I have a 1991 A/C with the automatic A/C. I absolutely hate this thing. I prefer a manual valve....fewer headaches. This is my 3rd C4 with these things. With that said...My A/C has a new control head, program module, compressor & clutch, lines, accumulator, self-adjusting orifice tube, evaporator core, condensor, freon, & a few sensors.

Here's the latest problem that has occured..... The AUTO settings reset to 75 degrees everytime I turn the key off, & the blower fan won't come on in AUTO mode. If I move the blower FAN controls higher or lower, the blower will come on, but if I press the AUTO FAN button located between the UP & DOWN FAN control buttons, or the main AUTO button, the fan just dies. I'm not sure if it's a relay, switch, the resistor, or what that's causing the AUTO & AUTO FAN problems.

Any ideas before I start testing piles of stuff on this thing?

THANKS!!!!!!!

 

I'm beginning to lead toward the Temperature Door Motor (or something controlling it) going bad, also. I used to hear it come on whenever I put the key in the car, but I haven't heard it lately.
This A/C is driving me nuts, & I'm in HOT & HUMID Florida.

 

I saw your question under Dale1990's thread and here was my reply:

I'd guess an intermittent in the power supply or ground - memory side since it happens once you turn off the key. Once memory is erased, nothing works for a few seconds (to a couple of minutes) while the Programmer learns the position of the temp door. 75 is usually the default, so if you disconnect and reconnect the battery and that temp shows up, you should probably look at the connector and make sure it's got a good ground because something is momentarily coming undone somewhere.

 

Before I read your reply, SunCr, I discovered tonight that the system holds memory if the key is only put into the accessory (ON) mode. I can remove the key, & come back later, & the settings I used are still in memory. However, as soon as I turn the key to the cranking position, everything gets erased. So, I at least know now that the memory is getting lost ONLY when I crank the car. The battery (dummy) light also came on while the car was running, so I've got to fix this before I end up with a serious electrical problem.

Yesterday, I tested every fuse, & all of the fusable links (those were fun) ,and they all checked out fine.

I agree with your reply, SunCr. There is something being lost somewhere. Tomorrow, I'm going to check power, ground, & the light blue information wires that run between the A/C control head, & the A/C programmer. That light blue wire also connects to the radio. However, my radio has been removed, so the radio shouldn't cause any problems. The service manual even says to remove the light blue wire from the radio in order to check the bus.

If anyone has anymore suggestions, please let me know. I'm slowly beginning to narrow things down at this point. It's just very time consuming to run all of these tests.

Thanks.