Hello I have checked fuses relays pressure switch fans connectors wires and anything else that I can search to check. First of all my relays are new. Not only new but the new ones are new and I have about 4 others to replace those just in case... Fuses all have been checked with resistance and are good. Also I have bypasses pressure switch no luck. Have also bypassed 12v to compressor hot and compressor engages. So here goes what I do know...

When I press the AC button in the cab the AC fan comes on like normal when the car is hot along with the cooling fan, but no AC Compressor. I have tried jumping the pressure switch no help. Now checking the loads on the relay tails I have 2 on each 12v constant when switch is on and 1 each ground. that leaves the lead to compressor and fan which is none with relay out.. You would think. My compressor lead shows almost 4v while car is running. Do I have grounding issues and if so WHERE!!! This has driven me nuts! One day the ac worked fine turned car off next day no AC. This happened literally after a mechanic added a partial can of R134. But not the same day was more like a week or so later. Any help or direction would be well listened to as I have racked my brain for any other ideas....

 

On for a couple more things. I also just now after I typed this hooked a negative wire from my battery to the yellow and blue wire on the thermo switch behind the glove box and the compressor still didnt come on. Then tried to bypass the pressure switch with this just in case it was "overfilled" and compressor still no go. I DO NOT have negative at the blue and yellow or the blue and white wire on thermo switch so I am guessing that means the ac switch on the dash is bad? But what would cause the compressor not to come alive with the pressure switch bypassed and red white straight to ground? Could there be some other issue somewhere I can not see?

 

Turn the key to the II position (or start the engine), turn on the a/c, turn on the blower inside of the car.

On the a/c pressure switch electrical connector, does the red/wht wire have 12V to ground? Also, does the blu/yel wire have continuity (~zero resistance or closed circuit) to ground? I always try to use a valve cover bolt as the ground when testing.

 

If I bypass the interior thermo switch yes. But only if I bypass it. Also like I said If I bypass the thermo switch or ground the blue Yellow on the switch and put a jumper for the pressure switch the compressor still doesnt come on.

 

If AC thermostat is open (blu/yel & blu/red to thermostat not shorted), thermostat is likely faulty. It should only open when thermister in evaporator senses low (~28F) temps. It could be a bad thermister or bad thermostat. Make sure thermostat has power on the blk/yel wire.

good luck

 

I'm back to my original question about voltage to the red/wht wire at the pressure switch. Also test for ground on the blu/yel (wasn't sure from your previous post if this was done). Measure the voltage like I described in the previous post.

Also, on the thermostat electrical connector, test for 12V on the blk/yel and blu/yel wires. Check continuity to ground on the blu/red wire.

Hopefully, this should help narrow down the problem.

One last question, why was R134 added?

 

I am pretty sure it was R134a I could be wrong but my air wasnt blowing cold and he said it was "just a smidge low" on refrigerant. Like I said everything worked fine till this moron worked on it minus it not blowing like a freezer. Ok on the thermostat connector you are talking about the one behind the glove box correct? And what is this switch called? I checked with the auto parts store locally and no one can find this switch to sell me. I had 12v on the blk yel and another wire when the "AC" switch was off. With the "AC" switch on I had nothing but to make sure I will go outside and check every wire possible and upload all of my readings so it will help you further. It was raining the night I tried this and I was getting soaked outside and frustrated my flashlight was dying so I tried to do as much as possible before I couldnt see. Be back in a couple hours with responses O yea I have a new dash switch I am going to replace while at it. Just in case

 

I'm coming in way late here.

I'm confused but that is nothing new.

The ac pressure switch under the battery....do you have continuity across the pins - yes no?

The AC compressor relay - drivers side, just under the rad support - the one with WHT, RED, BLK/YEL and RED/BLU wires to it....car on, ac on, blower on - what is the voltage on the:

BLK/YEL?
WHT?

 

Sorry it has been a while since I responded I will get answers for you tomorrow on that I have given up on everything since I checked every wire to ensure there wasnt any breaks by doing a check with a meter. Either way I will give you the answer to what you asked when I get off work tomorrow. I plan to save up some money and send it to a local mechanic soon in hopes it doesn't cost me an arm and ahole. I am seriously thinking it is something mechanical or electrical not faulty equipment.