HVAC problem - maybe the control module?

[Bushwack]

I was on the freeway at a record pace of 5-10 MPH for about an hour yesterday (with the a/c on) when I noticed the blower stopped blowing any air for about two minutes and then came back on its own (blowing cold air). The HVAC was set on medium/low at 72 degrees. The 'Service A/C' light did not come on. When I arrived home, as always I shut off the a/c then turned off the car.

This morning, the Service A/C light came on. I drove the car straight to my mechanic (recently had a new compressor installed). I gave him the keys to the car, turned on the ignition and all is good - no service a/c light and the a/c (blower) works fine (never had a chance to pull any codes). I've driven the car on an off today w/ the a/c on without a problem.

I can confidently rule out the compressor being the problem. My mechanic thinks (without troubleshooting) that the blower is OK because it does blow air. He thinks its the module. My question is, can the HVAC module turn itself off than back on (as it seems to have done initially)? Is it known that the HVAC control module can fail while its in operation?

I equate the module with a light switch. Turn on the switch and it doesn't fail - the light bulb will. Is this a fair comparison?

Thanks.

[Guest Richard D]

It could be the fan control module, or even a loose connector to the module. It is located under the hood passenger side above the fan and air handler. As far as the service message you may be borderline on your freon charge and if the ambient temp was cool that could cause a low pressure warning. There are other folks who may have had this problem and will offer their advice.

Good Luck,

Richard

[Guest Corvanti]

don't know if this will help:

http://forums.aaca.org/f116/cruise-control-vs-hvac-fan-328323.html

i haven't had a problem since that day. :confused:

[Guest Mc_Reatta]

How hot did it get under your hood while you were racing down the highway?

Did you check for BCM codes? If light came on a code should have been set.

Another possibility could be low airflow over the condenser caused the BCM to turn off the compressor due to too hot a temperature being reported by the high temp sensor. That would then allow the evaporator to get hotter than your set temp and shut down the blower until the situation corrected itself.

Did your radiator fans come on high speed during all this?

[Bushwack]

How hot did it get under your hood while you were racing down the highway?

Did you check for BCM codes? If light came on a code should have been set.

Another possibility could be low airflow over the condenser caused the BCM to turn off the compressor due to too hot a temperature being reported by the high temp sensor. That would then allow the evaporator to get hotter than your set temp and shut down the blower until the situation corrected itself.

Did your radiator fans come on high speed during all this?

Engine temp was OK. I tried duplicating the event by idling the car for 20 minutes w/o success. I don't think the compressor disengaged because I would have noticed.