Sorry I tried using the "search" but didn't work? My AC worked fine when I came home sat. night, got up to go to church sun. morning and the AC was blowing hot air out of the vents - the compressor was not coming on and the lights above the OFF & AUTO buttons were blinking. I have heard that the "Low Pressure Switch" can be bad causing the compressor not to come on, but I have no idea which one it is or how to check it instead of just buying a new one and hoping that is the problem. I don't think that the system is low on freon because when it was working it would cool immediatley, because I have also heard that when a system is low it will take a min. or so for it to really start cooling. ANY HELP here would greatly be appreciated

 

Do you have the auto (C68) A/C system? If so, press the fan up arrow and fan down arrow at the same time and hold for 5 seconds. That will enter the diagnostic mode and report any error codes back onto the temperature display. 00 is no error codes. If you get another error code, post what you find.

You can quick check for system pressure using the low side schrader valve (on the drier right in front of the p/s reservoir). Just like a tire, if you push it and nothing comes out, you somehow lost your freon charge.

 

I checked your profile and see you have an L98. Your drier is still mounted just behind the radiator, but I'm not sure where your p/s reservior is.

 

I pushed both the up & down buttons at the same time like you said and I got code -00, which you stated was no error code. I did this with the A/C turned on & off. I checked the primary fuse block at the side of the pass. door and the auxilary fuse block above th carpet panel beneath the pass. side dash and ALL fuses were good. I also got a test light and everything under the hood was dead except for the wire that goes to the blower and its relay, so now I am thinking that my main switch in the dash or that whole thing is bad? The only way I can see if any of the switches or compressor under the hood is bad is to test with a test light or to bypass the switches but I cannot do that if there is no power outside.

 

I don't know of any relay for the blower motor - it's controlled by a module on the evaporator housing. Compressor is controlled by the PCM which grounds a relay completing the clutch control circuit. If the relay shows a complete circuit on one side with the a/c request, but nothing on the output, it's probably needs to be replaced. I believe the signal side is brown from ignition or dash control, green/white back to the PCM for ground. Output to the coil is usually always green.

 

Sometimes the C68 electronic controller misplaces an 0 or 1 and will "lock up". One technique sometimes successfull is to remove the battery cable (or appropriate fuse) for about 30 seconds, reconnect, wait 2 full minutes, then check.

When performing this vodoo ritual, you are rebooting the electronic controller, the 2 minutes allows for the mixing doors full travel while the 'puter keeps track of position and movement.

This occasionally works. Since you had good A/C performance, doesn't sound like a slow leak and no codes. Let us know.

And SunCr would be my first choice for A/C info.

dlmeyers 90 coupe zf6 3 speed shocks

 

I disconnected the negative terminal on the battery like you said, waited then reconnected it and fired the car up and what would you know that my AC started blowin ice cold air once again. I let the car run for only a couple of minutes. But one thing I did notice is that the compressor would kick on and off about every 10-15 seconds, so now I am thinking that it might be a little low on freon because I dont think it should be cycling that quickly. Please let me know if I am wrong about this.

 

"on/off" cycling is a sure indicator that your system is low on freon.

 

Should have shown a trouble code 09. When the pressure switch - not the cycling or low pressure switch - sees low pressure, the PCM won't ground the clutch relay. This switch is mounted on the high pressure line and it's a thermistor with a 5 volt reference from the PCM. Resistance drops with low pressure - rises with high pressure, and the PCM uses this information to control the cooling fans (a/c on only) and compressor clutch engagement. Once the PCM receives a voltage indication that the charge is low, it disables a/c until the code is cleared; ie, the battery is disconnected.

The cycling or low pressure switch is after the PCM and basically keeps the evaporator from icing up. Since refrigerent pressures are dependent on the outside air temp, this switch is going to open the compressor clutch circuit or cause it to cycle when temperatures are low enough to cause icing (about anything below 60 degrees or until the system absorbs some engine heat). Once the engine is at operating temp, a fully charged system shouldn't cycle at all if it's 60 degrees or better. You can see if it's causing it to cycle by disconnecting it - it's either on the larger line from the evaporator or mounted on the accumulator. Once it's disconnected, put a paper clip across the harness terminals to keep the circuit from opening.

You should think about having the system pressure checked, or if you have a scanner, you can see what the pressure switch is sending to the PCM. Actually, a decent a/c shop is going to do both to verify that the pressure switch isn't out of whack. In fact, given that your a/c was ok and then quit, I'm not so sure that the pressure switch isn't at fault. It's a 3 wire switch mounted on the high pressure or smaller line from the condensor to the evaporator. You could backprobe it and see what the voltages are - I can't remember the leads, but I think red/black is the 5 volt reference, black is ground and whatever the other color is the return signal. It really doesn't matter what the wire colors are. You're looking for 5 volts on one of them and then something less on the other - ignore the ground. If the return is really low, it's either the switch or the charge is low.

 

I put one can of 134 in it and it stopped cycling for the couple of minutes I let the car run. I am going to drive the car and see if it cycles any once the engine temps get up to where they are supposed to be. I still think I am going to find a good AC shop and let them check the pressure and get it to where it is supposed to be. But for now its working and blowing ice cold. Will let you know if it cycles any or not.