I burned up the Lower fan motor on my 1991 C4 corvette. Got some gravel stuck between the fan blade and shroud. I have a new on on order. The control head for the A/C (controls climate of the cabin has the temp readouts etc..) is acting up and the AC will not come on. I have replaced the fan controller module and realized that it does the same thing with this module completly out of the circuit.
When I turn the key on the AC control head works, fan goes up and down can use all of the buttons no problem. If I starf the car all I get is dashes across the controll head window. I do not even have to start the car I can just turn the ignition past on and to were there is a momentary flash of power just before the starter comes in and the AC head goes to all dashes. If I turn the ignition off it resets itself and we are good until I try and start it.
I can control the fan speed etc.. until the car ignition is turned just past the on like I was going to start the car. I do not have both fan motors installed yet and thought that maybe the Aux fan motor being out might be the problem so i hooked it up to the main fan relay but it did the same thing. I cant beleive that both fans have to be installed to get this to work but maybe?
I will install tomorrow and see but I was wondering if anyone had every come across this problem?

 

I don’t think the AC will come on unless it’s charged up, so you might check that. Not an expert though.

 

Thanks I checked that. Completely full... good thought.

 

Lets start from square one. Was the A/C working recently? If so, was it cooling lesser then normal? How did you check the R134 level? Was it using one of those recharge gauges? I just picked up a 94 where the owner swore the A/C didn't work. 2lbs of refrigerant later..it gets colder then a eskimos titty lol When the condenser is low on refrigerant, it will not turn on to keep it from self destructing. This is dictated by the hi/low pressure switches. A common mistake if using the "recharge" gagues is that you make connect it and squeeze the trigger and it shows the "green" but still be low or empty. I had to keep force feeding it...until...the compressor kicked on and began taking in refrigerant. It cycle start-stopped the full first can and the needle would swing wildly as the condenser opened and closed. By the second can, the compressor stayed on and began cooling and the needle swings were less until it was topped up. I'd revist the refrigerant levels. 9/10 times...that's the cause for the condenser not switching on when prompted to.

 

yes just had it filled it is a controls problem. Every now and then the AC head works fine. I did pull the 5 am underhood fuse and it seemed to reset. I put the other fan motor on and drove the car for a 20 miles and it worked fine. Just every now and again the control head goes to all dashes and does not control.

 

Ahhhhh...yeah you may need to buy another control unit then. I think there is a dude on Ebay who rebuilds them for a fair price. I was looking into this dude to rebuild by LCD cluster.

 

You need to put down the can of refrigerant and step away until you have re-read your "AC Made EZ" book again. The condenser is nothing more than an air to gas/liquid heat exchanger. There is no moving parts(electrical or otherwise) and does not "turn on when prompted". It just patiently sits there and waits for high pressure/high temp gas to come to it. The compressor is what "turns on when prompted".

 

The AC portion of the system works. The control head is intermittent. Sometimes I get the inside and outside temperature readings and turn the key on start the car and the AC is very cold. Other times I turn the key on and there are nothing but dashes where the temperature readout should be.

Most of the I get the temperature reading turn the key to start the car there is a momentary loss of power while the car starts and the dashes show up. This started after the fan motor burned up and the wire to the fusable link burned up. The fusable link did not blow. I replaced the wire.

To reset this I can take the negative battery cable off and the dashes go away but the AC does not always work. I am wondering if I have a bad CCM?

 

I meant compressor....I got my terminology wrong. I have A/C gauges and have fixed several systems across various makes...but I am not an A/C expert. Just trying to simplify a mystifying topic many people make more complicated then it needs to be. However...I disagree with "does not turn on when prompted" lol I've seen compressors hooked up to switches...and theoretically...what is the A/C button? An electrical signal of you "prompting" the condenser to Engauge. Granted, several things have to be in place and present for it to do so...but...end of the day my point remains....9/10 times the reason for in-op A/C is low refrigerant.

 

this is true but the system is full and when called for the compressor clutch engages.

 

Anybody know anyone who can rebuild a control head? I have some checks to make but I think my control head may be the issue.

 

You can disagree all you want. At no point did I say the compressor "does not turn on when prompted". I said the condenser does not. This was in reference to your claim that it did.

 

oops my bad. The condenser as far as I know does not turn on or off it is just like a radiator? right? My point is that the AC works fine when it is controlinig properly but it is not being controled properly. I just got a scanner OBD1 I am going to check for codes. But holding the fan up and down buttons for 5 seconds shows no codes but does reset the control head to where the temperature readings come back but as soon as the key is turned the dashes come back --

 

If you are handy with tools here is a video on how to repair your A/C control head. I have had to do this twice to my 93 with the C68 option. it's not difficult to do, just take your time and clean everything like they show you.

 

thanks I will check-----on Youtube I suppose?

 

Great video

 

I rebuilt both my HVAC head unit and the control module under the dash. Check out my repair thread below starting at post #24. Batee sells everything you need and if your handy with a soldering iron you can do this. Other wise you can pull them out and Batee will rebuild them for you.

https://www.corvetteforum.com/forums...-thread-2.html

 

Thank you, I think I will start with the control head. The programmer I think controls where the AC or heat goes, defroster, floor etc. and that works.