Bob88Convertible

Here's a couple scenarios.

Driving along no air on one fan running. Car runs perfectly, temp stays in the 190's all day long. Even in stop and go traffic, only goes up in the low 200's, never sees 210.

Driving along 50-60 whatever, air running, both fans on. Temp stays in the 205-210 range, never hotter. Soon as I slow down or encounter any traffic, temp starts to rise. If I get in stop and go traffic, temp will go into the 220's and even 230's. If I start to drive steady again the temp will drop, or if I shut the air off and I'm still in heavy traffic the temp will still drop.

Just so you know, both fans work, radiator is perfectly clean.

Is it possible that the compressor is going bad and is causing a big enough drag on the motor that it will heat up when in traffic. The compressor does seem to cause more drag than normal when turning the air on.

Any thoughts would be appreciated.

jghmczo6

Sounds normal, a/c compressor will have some drag which causes the heat to rise, however 220-230 is not overly hot for a c-4.

Bullyj

tequilaboy

How do you know that 1 or both fans are running? Are you using manual switches for both fans?

From your username, I assume your talking about an 88 with the optional aux. fan.

The ecm controls the main fan normally 226 on/220 off. A thermal switch controls the aux. fan. something like 235 on/220 off, maybe even hotter.

Unless your programming has been modified, or the fans rewired or a lower temperature switch has been installed, your fans shouldn't be running under the conditions described.

The exception is with AC on and the AC high pressure flag set. In this case the ecm will also activate the main fan independent of the coolant temperature on/off switch points.

It sounds to me that at lower speeds, with the AC on, the AC high pressure flag is no longer set, resulting in the normal 226 on/220 off control for the main fan. This permits the temperature to rise until these temperatures are reached.

The aux. fan should not be activating until over 235 or more.

Expect it to run hot, unless changes have been implemented to the fan programming, aux fan switch or fan wiring.

Bob88Convertible

This is a new problem since I put new heads on the car. They are Brodix heads and did not have a place for the fan switch, so I have that on a manual switch. The fan behind the radiator comes on as soon as I turn on the a/c and the other is controlled manually, so I know they are both running.

The car never ran this hot with the a/c on prior to changing the heads, and the other side of that is, without the air on the car runs cooler than it did prior to putting on the new heads.

tequilaboy

Ok, now I understand your setup.

Having the AC on does not guarantee that the main fan will also run, even though you've observed it running with the AC on.

When below the normally programmed main fan on temperature of 226 F, this will only occur if the AC is on and the AC high pressure flag is also set. This flag may cycle on and off following the compressor cycles and may or may not be set depending upon conditions within the AC system, level of charge, etc.

There is an AC high pressure switch that is read by the ecm to set this flag on or off. I don't know if it is normally open or normally closed, but thats not really important in this discussion.

It could be that your AC is simply not maintaining enough pressure to keep the switch activated (and hence the AC high pressure flag) under all conditions described which would result in higher coolant temperatures until the normal 226 F main fan on threshold is reached if the airflow through the radiator is insufficient.

The aux. fan being manually controlled, in this case should be running when activated by the switch, so thats not part of the issue.

89 Bob L

How is the coolant level? After replacing the heads, you may not have added enough coolant or the proper mix. Remove the radiator cap, start the engine and let it idle up to operating temperature so the thermostat opens. Look inside the radiator and check the coolant level, Raise the idle to approx. 13-1400 rpm and the coolant level may drop. Add coolant at 13-1400 rpm and put the radiator cap back on.

Just a thought

89 Bob L

In addition to the above, make sure the heat is on full when checking the coolant level

TLewis4095

Stop by the shop, we will do a complete A/C check for free.

Bob88Convertible

Yep, did that.

Didn't do this tho, have to check it again.

What are your hours over there??

SunCr

Fans shouldn't be on at cruise and in some cases, particularly the pusher, it can restrict air flow.

a/c operation, at idle, should always be a few degrees cooler than without it. Main fan runs sooner - and longer - because the monitored parameter is the temperature (pressure) at the condensor which is generally no more than 120 to 140 degrees. You swapped out the heads and that means you moved the compressor and accumulator which means there's a possibility one of the lines got crimped. It doesn't take much to create a restriction and that can back it up creating more pressure which creates more heat. Examine your work or better yet, after the a/c shop hooks up a manifold gage set, post what the pressures are along with the outside air temp.

TLewis4095

www.RevXtreme, Hours are 9-6 M-F, 10-5 Sat.