Normal Operating Temperature
05-23-2016, 06:42 PM
#1
Advanced
Thread Starter
Normal Operating Temperature
What is normal operating temperature for my (2001) C5 Coupe? At what temperature should I get concerned about it running too hot in stop and go traffic? Watching the gage, it seems to creep way in excess of 220 almost to the red line. It will cool back down as you drive constant moving, even at low speeds. It does this whether the AC is on or off. Is something out of the norm on this?
05-23-2016, 07:35 PM
#3
Advanced
Thread Starter
Ok, I understand 220 is no problem, but you didn't answer the questions... As the gage creeps toward the red lines, What temp should I get concerned? Is this normal on C5's?
Where do I find related threads?
Where do I find related threads?
05-24-2016, 12:19 PM
#4
Le Mans Master
Written by ET
Coolant sweet spot 190/210 F Oil sweet spot 210/230
There is a sweet spot for these motors. This sweet spot is designed for efficiency and longevity. Once the engine is at operating temp Oil and coolant should be no colder than the designed temp. The engine is designed to run between the sweet spot and warmer. NOT the sweet spot and colder... Hot is your friend.. tuners will tell you different, but then tuners are paid to giver you HP. not guarantee longevity.. AS I've said here for 15 years... Everything is a trade off. want more HP, run colder, get it tuned, and lose the back end... Longevity. Use regular gas? save a few bucks. Ignore ping, and detonation. allow your car to run at reduced timing, reduced performance, allow internal damage ( pre-ignition )to beat your engine to death.
Cooling System Description and Operation
Cooling Fan Control
The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).
Engine Coolant Indicator(s)
COOLANT OVER TEMP
The IPC illuminates the COOLANT OVER TEMP indicator in the message center when the following occurs:
The PCM detects that the engine coolant temperature exceeds 124°C (256°F). The IPC receives a class 2 message from the PCM indicating the high coolant temperature.
The IPC will also illuminate the CHECK GAGES indicator and a chime sounds when this condition exists.
Cooling System
The cooling system's function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. The cooling system is designed to remove approximately one-third of the heat produced by the burning of the air-fuel mixture. When the engine is cold, the system cools slowly or not at all. This allows the engine to warm quickly.
Cooling Cycle
Coolant is drawn from the radiator outlet and into the water pump inlet by the water pump. Some coolant will then be pumped from the water pump, to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost.
Coolant is also pumped through the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders where it absorbs heat.
The coolant is then forced through the cylinder head gasket openings and into the cylinder heads. In the cylinder heads, the coolant flows through the water jackets surrounding the combustion chambers and valve seats, where it absorbs additional heat.
Coolant is also directed to the throttle body. There it circulates through passages in the casting. During initial start up, the coolant assists in warming the throttle body. During normal operating temperatures, the coolant assists in keeping the throttle body cool.
From the cylinder heads, the coolant is then forced to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine is warmed, or it will flow through the thermostat and into the radiator where it is cooled and the coolant cycle is completed.
Operation of the cooling system requires proper functioning of all cooling system components. The cooling system consists of the following components:
Coolant
The engine coolant is a solution made up of a 50-50 mixture of DEX-COOL and clean drinkable water. The coolant solution carries excess heat away from the engine to the radiator, where the heat is dissipated to the atmosphere.
Radiator
The radiator is a heat exchanger. It consists of a core and two tanks. The aluminum core is a crossflow tube and fin design. This is a series of tubes that extend side to side from the inlet tank to the outlet tank. Fins are placed around the outside of the tubes to improve heat transfer from the coolant to the atmosphere. The inlet and outlet tanks are molded with a high temperature, nylon reinforced plastic. A high temperature rubber gasket seals the tank flange edge. The tanks are clamped to the core with clinch tabs. The tabs are part of the aluminum header at each end of the core. The radiator also has a drain **** which is located in the bottom of the left hand tank. The drain **** includes the drain **** and drain **** seal.
The radiator removes heat from the coolant passing through it. The fins on the core absorb heat from the coolant passing through the tubes. As air passes between the fins, it absorbs heat and cools the coolant.
During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. This is an advantage to the cooling system. Coolant without bubbles absorbs heat much better than coolant with bubbles.
Pressure Cap
The pressure cap is a cap that seals and pressurizes the cooling system. It contains a blow off or pressure valve and a vacuum or atmospheric valve. The pressure valve is held against its seat by a spring of predetermined strength, which protects the radiator by relieving pressure if it exceeds 15 psi. The vacuum valve is held against its seat by a spring, which permits opening of the valve to relieve vacuum created in the cooling system as it cools off. The vacuum, if not relieved, might cause the radiator to collapse.
The pressure cap allows pressure in the cooling system to build up. As the pressure builds, the boiling point of the coolant goes up as well. Therefore, the coolant can be safely run at a temperature much higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant is, the faster the heat moves from the radiator to the cooler, passing air. The pressure in the cooling system can get too high, however. When the pressure exceeds the strength of the spring, it raises the pressure valve so that the excess pressure can escape. As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open, allowing outside air into the cooling system. This equalizes the pressure in the cooling system with atmospheric pressure, preventing the radiator from collapsing.
Surge Tank
The surge tank is a plastic tank with a pressure cap mounted to it. The tank is mounted at a point higher than all other coolant passages. The surge tank provides an air space in the cooling system. The air space allows the coolant to expand and contract. The surge tank also provides a coolant fill point and a central air bleed location.
During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. This is an advantage to the cooling system. Coolant without bubbles absorbs heat much better than coolant with bubbles.
Air Baffles and Seals
The cooling system uses deflectors, air baffles and air seals to increase system cooling. Deflectors are installed under the vehicle to redirect airflow beneath the vehicle to flow through the radiator and increase cooling. Air baffles are also used to direct airflow into the radiator and increase cooling. Air seals prevent air from bypassing the radiator and A/C condenser. Air seals also prevent recirculation of the air for better hot weather cooling and A/C condenser performance.
Water Pump
The water pump is a centrifugal vane impeller type pump. The pump consists of a housing with coolant inlet and outlet passages and an impeller. The impeller is a flat plate mounted on the pump shaft with a series of flat or curved blades or vanes. When the impeller rotates, the coolant between the vanes is thrown outward by centrifugal force. The impeller shaft is supported by one or more sealed bearings. These sealed bearings never need to be lubricated. With a sealed bearing, grease cannot leak out, and dirt and water cannot get in.
The purpose of the water pump is to circulate coolant throughout the cooling system. The water pump is driven by the crankshaft via the drive belt.
Thermostat
The thermostat is a coolant flow control component. It's purpose is to regulate the operating temperature of the engine. It utilizes a temperature sensitive wax-pellet element. The element connects to a valve through a piston. When the element is heated, it expands and exerts pressure against a rubber diaphragm. This pressure forces the valve to open. As the element is cooled, it contracts. This contraction allows a spring to push the valve closed.
When the coolant temperature is below 91°C (195°F), the thermostat valve remains closed. This prevents circulation of the coolant to the radiator and allows the engine to warm up quickly. After the coolant temperature reaches 91°C (195°F), the thermostat valve will open. The coolant is then allowed to circulate through the thermostat to the radiator where the engine heat is dissipated to the atmosphere. The thermostat also provides a restriction in the cooling system, even after it has opened. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block.
Transmission Oil Cooler
The transmission oil cooler is a heat exchanger. It is located inside the right side end tank of the radiator. The transmission fluid temperature is regulated by the temperature of the engine coolant that surrounds the oil cooler as the transmission fluid passes down through the cooler.
The transmission oil pump, pumps the fluid through the transmission oil cooler feed line to the oil cooler. The fluid then flows down through the cooler while the engine coolant absorbs heat from the fluid. The fluid is then pumped through the transmission oil cooler return line, to the transmission.
Coolant sweet spot 190/210 F Oil sweet spot 210/230
There is a sweet spot for these motors. This sweet spot is designed for efficiency and longevity. Once the engine is at operating temp Oil and coolant should be no colder than the designed temp. The engine is designed to run between the sweet spot and warmer. NOT the sweet spot and colder... Hot is your friend.. tuners will tell you different, but then tuners are paid to giver you HP. not guarantee longevity.. AS I've said here for 15 years... Everything is a trade off. want more HP, run colder, get it tuned, and lose the back end... Longevity. Use regular gas? save a few bucks. Ignore ping, and detonation. allow your car to run at reduced timing, reduced performance, allow internal damage ( pre-ignition )to beat your engine to death.
Cooling System Description and Operation
Cooling Fan Control
The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).
Engine Coolant Indicator(s)
COOLANT OVER TEMP
The IPC illuminates the COOLANT OVER TEMP indicator in the message center when the following occurs:
The PCM detects that the engine coolant temperature exceeds 124°C (256°F). The IPC receives a class 2 message from the PCM indicating the high coolant temperature.
The IPC will also illuminate the CHECK GAGES indicator and a chime sounds when this condition exists.
Cooling System
The cooling system's function is to maintain an efficient engine operating temperature during all engine speeds and operating conditions. The cooling system is designed to remove approximately one-third of the heat produced by the burning of the air-fuel mixture. When the engine is cold, the system cools slowly or not at all. This allows the engine to warm quickly.
Cooling Cycle
Coolant is drawn from the radiator outlet and into the water pump inlet by the water pump. Some coolant will then be pumped from the water pump, to the heater core, then back to the water pump. This provides the passenger compartment with heat and defrost.
Coolant is also pumped through the water pump outlet and into the engine block. In the engine block, the coolant circulates through the water jackets surrounding the cylinders where it absorbs heat.
The coolant is then forced through the cylinder head gasket openings and into the cylinder heads. In the cylinder heads, the coolant flows through the water jackets surrounding the combustion chambers and valve seats, where it absorbs additional heat.
Coolant is also directed to the throttle body. There it circulates through passages in the casting. During initial start up, the coolant assists in warming the throttle body. During normal operating temperatures, the coolant assists in keeping the throttle body cool.
From the cylinder heads, the coolant is then forced to the thermostat. The flow of coolant will either be stopped at the thermostat until the engine is warmed, or it will flow through the thermostat and into the radiator where it is cooled and the coolant cycle is completed.
Operation of the cooling system requires proper functioning of all cooling system components. The cooling system consists of the following components:
Coolant
The engine coolant is a solution made up of a 50-50 mixture of DEX-COOL and clean drinkable water. The coolant solution carries excess heat away from the engine to the radiator, where the heat is dissipated to the atmosphere.
Radiator
The radiator is a heat exchanger. It consists of a core and two tanks. The aluminum core is a crossflow tube and fin design. This is a series of tubes that extend side to side from the inlet tank to the outlet tank. Fins are placed around the outside of the tubes to improve heat transfer from the coolant to the atmosphere. The inlet and outlet tanks are molded with a high temperature, nylon reinforced plastic. A high temperature rubber gasket seals the tank flange edge. The tanks are clamped to the core with clinch tabs. The tabs are part of the aluminum header at each end of the core. The radiator also has a drain **** which is located in the bottom of the left hand tank. The drain **** includes the drain **** and drain **** seal.
The radiator removes heat from the coolant passing through it. The fins on the core absorb heat from the coolant passing through the tubes. As air passes between the fins, it absorbs heat and cools the coolant.
During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. This is an advantage to the cooling system. Coolant without bubbles absorbs heat much better than coolant with bubbles.
Pressure Cap
The pressure cap is a cap that seals and pressurizes the cooling system. It contains a blow off or pressure valve and a vacuum or atmospheric valve. The pressure valve is held against its seat by a spring of predetermined strength, which protects the radiator by relieving pressure if it exceeds 15 psi. The vacuum valve is held against its seat by a spring, which permits opening of the valve to relieve vacuum created in the cooling system as it cools off. The vacuum, if not relieved, might cause the radiator to collapse.
The pressure cap allows pressure in the cooling system to build up. As the pressure builds, the boiling point of the coolant goes up as well. Therefore, the coolant can be safely run at a temperature much higher than the boiling point of the coolant at atmospheric pressure. The hotter the coolant is, the faster the heat moves from the radiator to the cooler, passing air. The pressure in the cooling system can get too high, however. When the pressure exceeds the strength of the spring, it raises the pressure valve so that the excess pressure can escape. As the engine cools down, the temperature of the coolant drops and a vacuum is created in the cooling system. This vacuum causes the vacuum valve to open, allowing outside air into the cooling system. This equalizes the pressure in the cooling system with atmospheric pressure, preventing the radiator from collapsing.
Surge Tank
The surge tank is a plastic tank with a pressure cap mounted to it. The tank is mounted at a point higher than all other coolant passages. The surge tank provides an air space in the cooling system. The air space allows the coolant to expand and contract. The surge tank also provides a coolant fill point and a central air bleed location.
During vehicle use, the coolant heats and expands. The coolant that is displaced by this expansion flows into the surge tank. As the coolant circulates, air is allowed to exit. This is an advantage to the cooling system. Coolant without bubbles absorbs heat much better than coolant with bubbles.
Air Baffles and Seals
The cooling system uses deflectors, air baffles and air seals to increase system cooling. Deflectors are installed under the vehicle to redirect airflow beneath the vehicle to flow through the radiator and increase cooling. Air baffles are also used to direct airflow into the radiator and increase cooling. Air seals prevent air from bypassing the radiator and A/C condenser. Air seals also prevent recirculation of the air for better hot weather cooling and A/C condenser performance.
Water Pump
The water pump is a centrifugal vane impeller type pump. The pump consists of a housing with coolant inlet and outlet passages and an impeller. The impeller is a flat plate mounted on the pump shaft with a series of flat or curved blades or vanes. When the impeller rotates, the coolant between the vanes is thrown outward by centrifugal force. The impeller shaft is supported by one or more sealed bearings. These sealed bearings never need to be lubricated. With a sealed bearing, grease cannot leak out, and dirt and water cannot get in.
The purpose of the water pump is to circulate coolant throughout the cooling system. The water pump is driven by the crankshaft via the drive belt.
Thermostat
The thermostat is a coolant flow control component. It's purpose is to regulate the operating temperature of the engine. It utilizes a temperature sensitive wax-pellet element. The element connects to a valve through a piston. When the element is heated, it expands and exerts pressure against a rubber diaphragm. This pressure forces the valve to open. As the element is cooled, it contracts. This contraction allows a spring to push the valve closed.
When the coolant temperature is below 91°C (195°F), the thermostat valve remains closed. This prevents circulation of the coolant to the radiator and allows the engine to warm up quickly. After the coolant temperature reaches 91°C (195°F), the thermostat valve will open. The coolant is then allowed to circulate through the thermostat to the radiator where the engine heat is dissipated to the atmosphere. The thermostat also provides a restriction in the cooling system, even after it has opened. This restriction creates a pressure difference which prevents cavitation at the water pump and forces coolant to circulate through the engine block.
Transmission Oil Cooler
The transmission oil cooler is a heat exchanger. It is located inside the right side end tank of the radiator. The transmission fluid temperature is regulated by the temperature of the engine coolant that surrounds the oil cooler as the transmission fluid passes down through the cooler.
The transmission oil pump, pumps the fluid through the transmission oil cooler feed line to the oil cooler. The fluid then flows down through the cooler while the engine coolant absorbs heat from the fluid. The fluid is then pumped through the transmission oil cooler return line, to the transmission.
Last edited by 73Corvette; 05-24-2016 at 12:24 PM.
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05-24-2016, 12:30 PM
#5
Le Mans Master
When you do a search DO NOT use the forum search feature... use GOOGLE it will usually have several options from the C5 forum as well as the LS1 forum and others you can do your research from there and then come back to the forum to ask any questions you still may have...
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05-24-2016, 12:31 PM
#6
Tech Contributor
Member Since: Dec 1999
Location: Anthony TX
Posts: 32,736
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1,585 Posts
CI 6,7,8,9,11 Vet
St. Jude Donor '08
230 in traffic would be my HIGH!
If it started to register more than 230 then I would start to look for cooling system problems. Low coolant, poor air flow, fan issues ect ect.
Bill
If it started to register more than 230 then I would start to look for cooling system problems. Low coolant, poor air flow, fan issues ect ect.
Bill
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Clayton59 (05-29-2016)
05-24-2016, 12:37 PM
#7
Le Mans Master
debris in and or between the A/C condenser and the radiator is probably the MOST common issue...for overheatingThe ONLY really good way to clean the RADIATOR is to REMOVE IT... that's right REMOVE IT...
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TRAKOUT (05-25-2016)
06-06-2016, 04:53 PM
#8
Advanced
Thread Starter
Ok, so there is a lot of debris between the radiator and AC condenser. I cleaned it out the best I can without removing the radiator... So, If I'm understanding this correctly, If my car is sitting, running idle speed in the driveway, water temp at 215, BOTH fans should be running? on mine only the driver side fan (upper fan) is running. While sitting idle in the driveway for 30 minutes after reaching 198 mark, I cant get the temp to exceed 219. However in stop and go traffic, temp will creep up well in excess of the 230 mark very quickly. I don't know if the right hand fan is coming on or not. I'll have to check on this next time I'm in stop and go traffic.
06-06-2016, 05:26 PM
#10
Racer
If I read the electrical schematics correctly, the last time whey were posted (someone please correct me if I'm wrong), you should never have just one fan running. You should have either two at low speed or two at high speed. Assuming the fan control is still stock.
Jim
Jim
06-06-2016, 05:34 PM
#11
Instructor
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06-06-2016, 05:38 PM
#12
Le Mans Master
06-06-2016, 06:59 PM
#13
Safety Car
Max is 230 when left on idle or even sitting in traffic. On all stock settings, meaning no fan adjustment.
While on freeway it should average 195 ish.
Street will average 210-220ish.
Now if your temp is above 230 then could be the following that may caud issue:
Bad coolant
Block radiator
Bad radiator
Bad water pump
If you have a leak then check everything.
Other than that if you have stock fan settings, them 230 will be the max it should get then the fans will cool it off.
Plain and simple if you reaching red line, I'd shut the car down and start finding thw problem because chances you'll destroy something or head gaskets can blow out.
All easy to fix if you can do it.
While on freeway it should average 195 ish.
Street will average 210-220ish.
Now if your temp is above 230 then could be the following that may caud issue:
Bad coolant
Block radiator
Bad radiator
Bad water pump
If you have a leak then check everything.
Other than that if you have stock fan settings, them 230 will be the max it should get then the fans will cool it off.
Plain and simple if you reaching red line, I'd shut the car down and start finding thw problem because chances you'll destroy something or head gaskets can blow out.
All easy to fix if you can do it.
Last edited by My Vette Life; 06-06-2016 at 07:06 PM.
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06-07-2016, 04:01 AM
#15
Melting Slicks
Member Since: Aug 2013
Posts: 2,491
Received 312 Likes
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227 Posts
St. Jude Donor '15-'16-'17-'18-'19-'20-'21-'22
Here are the normal temperature ranges:
Normal Temperature Range.pdf
Factory temp settings are low speed on at 226 degrees and off at 219 degrees. High speed on at
235 degrees and revert to low speed at 226 degrees. As stated both fans run at low speed and high
speed and fans are commanded off by the PCM when the vehicle speed exceeds 35mph.
You can force low speed operation at 185 degrees by turning on the AC. High speed operation with
AC on is still 235 degrees.
Normal Temperature Range.pdf
Factory temp settings are low speed on at 226 degrees and off at 219 degrees. High speed on at
235 degrees and revert to low speed at 226 degrees. As stated both fans run at low speed and high
speed and fans are commanded off by the PCM when the vehicle speed exceeds 35mph.
You can force low speed operation at 185 degrees by turning on the AC. High speed operation with
AC on is still 235 degrees.
Last edited by laurent_zo6; 06-07-2016 at 04:02 AM.
06-07-2016, 07:05 AM
#16
Advanced
Thread Starter
06-13-2016, 04:11 PM
#19
Cool it switch
Aftermarket, it's a wireless remote controller for the right fan and high speed relay. Comes complete and installs in minutes. Hid my wireless controller in the ashtray on top of the cigarette lighter opening. Works great, keeps temp in the sweet spot.
06-24-2016, 08:30 AM
#20
Advanced
Thread Starter
Ok, so I looked at the relays. two of the three were apparently burnt.There are also indications that something got hot under these two relays (slightly melted plastic at the holes where the electrodes plug in). is there a schematic to show how to jump the relays to check the fans???
Cooling Fan Control
The engine cooling fan system consists of two electrical cooling fans and three fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage and ignition 1 voltage from the underhood electrical center. The ground path is provided at G102.
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan 3 relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 3 relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the cooling fan 2 relay coil is energized closing the relay contacts and provides battery positive voltage on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph).