Gl!tch

Ok, Masters of Vettedom...Can anyone give me leads as to the directions I should take to find out why I have no heat or warm air from my defroster or heater? Fans/blowers all run...and I understand to check fuses....and then......??

93 Coupe...and yes, the temp is bumped up on the controls.

Thanks always for the input!

NEVRL8T

I bet its the heater core. Smell any coolant? Floor damp on passenger side?

My heater core is going out but my floor is not damp. I can definetly smell coolant when I run the heater/defrost and I get a light film on the windshield at times and my defrost doesn't work hardly at all.

Gl!tch

None of the above...just good ol' cool air.

shadowman1

Do you have manual or automatic temp control?

LMDNC5

I betting on a vacumn leak used to control heater controls

The Hobbit

On my 86 it was the heater valve, the lever moved ok but just spun around the shaft on the valve.

Barry

shadowman1

It could be the head unit or the temp sensors. Blend door actuator, heater valve.
Auto air...
One photosensitive and two temperature variable resistors (sensors) are connected to the Heater and A/C Programmer to provide in-car and outside temperature information. The In-Car and Outside Sensors are thermistors which decrease in resistance as the temperature of the device increases. The Sun Load Sensor resistance decreases as light increases. These sensors are connected to fixed resistors in the Heater and A/C Programmer to provide a voltage input which varies according to the change in resistance. Ground reference for the sensors is provided by the Heater and A/C Programmer.

Circuits within the Heater and A/C Programmer use the input from the In-Car Sensor and the Sun Load Sensor in conjunction with the set temperature selected to determine whether the air should be heated or cooled to bring the inside of the vehicle to the selected temperature. The input from the Outside Sensor is used to determine the amount of heating or cooling required to bring the temperature inside the vehicle to the selected value as quickly as possible.

The Air Mix Valve Motor controls the position of the Air Mix Valve. The Motor can be operated in either direction by the polarity of the voltage applied to it. When the solid state switch grounds terminal "C8" in the Heater and A/C Programmer, then terminal "5", of the Air Mix Valve Actuator is positive. If the condition of the solid state switches is reversed and terminal "C7" is grounded, then terminal "6" of the Air Mix Valve Actuator is positive and the Motor runs in the reverse direction.

The Position Feedback Pot indicates the position of the Valve at any point of its travel. As the Valve moves between fully open and fully closed, the voltage input at terminal "D13" on the Heater and A/C Programmer will vary between 0 and 5 volts.

Manual air...

The Air Delivery system consists of the Heater and A/C Control Head, a solenoid assembly, vacuum actuators and air valves. The function of these are described below.

HEATER AND A/C CONTROL HEAD

With the Ignition "ON," voltage is applied through the A/C Fuse to the Heater and A/C Control Assembly. The operating mode of the system is determined by switches on the front panel. Output grounds to the Heater and A/C Solenoid Assembly determine which air valves are to be operated.

HEATER AND A/C SOLENOID ASSEMBLY

The Heater and A/C Solenoid Assembly contains the solenoid valves that control the vacuum actuators. There is one solenoid for each vacuum actuator. When the solenoids are de-energized, the valves vent the vacuum actuators, allowing the vacuum actuator to return to the vent position determined by a spring.

TEMPERATURE VALVE

The Temperature Valve is controlled by the Temperature Lever in the Heater and A/C Control Assembly. With the selector in "COLD," the valve is in the "COLD" position. This prevents air from blowing across the Heater Core. With the selector in any position but "COLD," the Temperature Valve is open. According to the selector position, some or all of the air blows across the Heater Core.

A/C DEFROST VALVE

The A/C Defrost Valve is controlled by the A/C Defrost Valve Vacuum Actuator. When the Mode Selector is in "MAX," "NORM," "BI-LEVEL" or "VENT," vacuum is applied through the RED hose to the A/C Defrost Valve Vacuum Actuator. This pulls the A/C Defrost Valve to position B and prohibits air from entering the Defroster Outlet.

If the Mode Selector is in "HEATER" or "DEFROST," no vacuum is applied and the A/C Defrost Valve moves to position A, thereby forcing the air out the Defroster Outlet.

FRONT MODE VALVE

When the Front Mode Valve Vacuum Actuator receives vacuum (only in "HEATER" Mode) the Front Mode Valve is pulled to position B. This prevents any air from flowing to the A/C and Defroster Outlets and forces it to go to the Heater Outlets. In any other mode, the Front Mode Valve is in position A, blocking the Heater Outlets.

REAR MODE VALVE

The Rear Mode Valve is controlled by the Rear Mode Valve Vacuum Actuator. When the Mode Selector is in "MAX," "NORM," "VENT" or "DEFROST," vacuum is applied to the Rear Mode Valve Vacuum Actuator which moves the Rear Mode Valve to position A. This allows air to flow to both the A/C and the Heater Outlets. In any other mode, the Rear Mode Valve is in position B.

RECIRCULATION VALVE

The Recirculation Valve Vacuum Actuator has no vacuum applied for every Mode Selector position except for "MAX." The actuator bellows are expanded. The Recirculation Valve is in position A. This opens the Outside Air Inlet and lets outside air into the Plenum.

When the Mode Selector is moved to "MAX," vacuum is applied to the Recirculation Valve Vacuum Actuator. The bellows are drawn in and the valve is moved to position B. Air from inside the vehicle is pulled into the Plenum.

redwing76

The 1st thing that Id check is the coolant level. If its to low it won't fill the heator core. Had that happen it was a leaking water pump.

Gl!tch

Shadow -- Auto Climate --read you tech post...now I just have to find pics of the pieces and parts to look at...Thanx

shadowman1

do you have a fax?

shadowman1

do you have a fax? or email me .. djboyd1@hotmail.com

samsonb

Where is the heater valve and what does it do?

Mine is an 89 with auto climate control.

Red Dwarf

Did you check the vacumn valve under the pass/side fuel rail cover?

Gl!tch

Shadow -- Got an efax number ...goes directly to my email (free too!).. the number is 702-975-3696. You can dial it from any fax machine and it gets converted and sent to my email. Email address also is floydbolton@charter.net Thanks! Floyd

shadowman1

Check your email.

SunCr

There's no heat valve on this Year (or the '89 for that matter).

If the air blows where it should blow, there isn't a vacuum problem.

You start by making sure air is getting to the heater core. Remove the Blower Module or Resistor Pod on the left side of the Evaporator Case and look inside. There's a door in there and it should move between hot and cold, cold and hot, 60 and 90, etc. If it does, the controls are working and you simply have a plugged up heater core. Some of the later years use a check valve from the source which other members have posted as being the problem. Otherwise, you can try flushing the core by removing the hoses and using your garden hose or compressed air. Go easy on the pressure as system pressure usually doesn't exceed 18 psi.

shadowman1

GM calls the blend and air diverter doors "valves". See above post for reference.

TEMPERATURE VALVE

The Temperature Valve is controlled by the Temperature Lever in the Heater and A/C Control Assembly. With the selector in "COLD," the valve is in the "COLD" position. This prevents air from blowing across the Heater Core. With the selector in any position but "COLD," the Temperature Valve is open. According to the selector position, some or all of the air blows across the Heater Core.

SunCr

Early C4's and most GM's through the mid 80's used a vacuum/mechanical valve controlling coolant flow to the core. The '93 and the '89 do not.

Your description sounds like a Manual Air setup wherein the temp door is controlled by a cable from the Controls. Electronic Air, for the '93, communicates with a Processor - the Programmer - over serial data lines. That device then operates an electrical motor which is connected to the Temp Door (which is between the Evaporator and Heater Cores). Door position is calculated from the Temperature Setting and if the Controls are at anything other than 60 and 90, input from the Outside and Inside Temp Sensors. This Year (and I can't remember exactly when this started) might also monitor the Coolant Temp Sensor and for those Years that do, heat doesn't flow until the signal is somewhat north of 100 degrees. All of this is designed to be diagnosed with a bi-directional scanner through the Body (CCM) Computer Link. Most don't have access to such, so doing what I outlined is a quick way to see if the door is even moving - for either, Manual or Electronic Air for that matter.

'89 Electronic Air isn't as sophisticated as the '93. The Controls operate as the Processor, but it still relies on an electric motor to move the Temp Door. Again, removing the Blower Module (Electronic) or Resistor Pod (Manual) is still the best way to visualize what that door is or isn't doing.

It would really help to keep HVAC questions to a specific Year. GM continually redesigned these things adding enough subtle differences to where what works on one, isn't going to work on the other.

93v

My 93 w/climate control had the same problem.Are both your'e hoses going in and out of the heater core the same temp? If not you may have a blocked heater core.I had to pull off the hoses and flush out the core with a hose couldn't believe all the junk that came out of there. First you may want to check to see if your'e air control door is working properly. Mine worked great after flushing the core

dudman

My 93 too had the same problem. I was fooled in thinking since both heater hoses from the firewall were hot that coolant was flowing through the heater core. That assumption was incorrect. I was able to unhook the hoses and flush with a garden hose. Mine too had a lot of crap in there and once flushed worked like a charm.