1991 Oldsmobile 98 AC Compressor and Switches Not Getting Power
 

I have a 1991 Olds 98 Regency Elite and have an issue with no AC.

So I'll start from the beginning. I got the car off my father which was sitting in a garage for the last 18 years, car only has 77,000km. Once we changed out the battery and got it running I noticed the AC Compressor would click in and out quickly (every couple of seconds) when idling. (can't tell when driving) We thought that it was low on the refrigerant cause of the issue and that it was blowing cool air and not cold. So we ended up taking it to a local shop to have it recharged. After about 2 hours of waiting they tell us that they can't get the compressor to kick in and that they can't do anything as the car has r12 in it and the only thing they can do is convert it to r134a. We ended up leaving to try and solve the issue first ourselves as we are handy and want to save some change. Once we got home we noticed that the mechanics had drained what was left of the refrigerant and now the compressor no longer clicks in at all.

So, instead of spending lots of money converting the system from r12 to r134a we searched and were able to buy a 30lbs bottle of r12. The first time filling the system we couldn't get more than 1.51 lbs of refrigerant in when it specifies 2.42lbs, and when turning on the car to get the compressor to kick in to accept the ac it would not no matter what. Without the compressor kicking in it wouldn't take more than the 1.51lbs.

So the next day came and we decided to do some research, we saw that people would jump/bridge the pressure switch located by the drier/accumulator to kick in the compressor, so we tried that and nothing. We afterwards took a test light and saw that once the car turned on the pressure switch would only have power for a split second and then turn off. So no power to the pressure switch... So we also decided to try and test power to the other pressure switch/refrigerant pressure switch connected to a line right beside the compressor, the power(green and white wire) had constant power when the car was on, so that is good. Next, we tested another connector connect to the back of the compressor (it was red and on the opposite side of the clutch). It was the same as the pressure switch by the drier, the power wire would only switch on for a split second and then immediately no power. And finally just to confirm we tested the connector that is beside the clutch, responsible for kicking in the clutch. And to no surprise no power at all.

So to dive into our investigation we applied an independent power source 12v to the connector on the clutch and we could hear it click in, so we know that the clutch and compressor work in that way. Next, we found somewhere that you can jump the AC relay and that it will kick in the compressor too. So we held a vacuum on the system with no issues at all, went to put the refrigerant in and we jumped the relay when turning the car on and the compressor works and stays on, YEAH! expect after we filled the system and replugged in the relay the compressor no longer kicks in at all. We tried switching a 100% working relay ( the horn relay) and the Compressor still doesn't click in, so we know it's not a relay issue. We have checked all the fuses in the car, no issues. We have checked the pressure switch by the drier by checking if it has resistance on a multimeter, and yes it does indeed have resistance (forgot what the number was). And I have even opened up behind the radio and climate control to get access to the interior temperature sensor thingy. We tested that sensor by checking the resistance while we applied hot and cool air by a hairdryer, and yes the resistance increased with hot air and when down with cool air.

Most recently we checked to see what terminals on the relay had power, so we checked, and terminal 30 had constant power with the car off, and 85 had power once the car was on. the other two 86 and 87 had no power, as 86 I believe is ground, and 87 is what the power switches too.

Honestly, no idea where to go from here, only thing we can think of last is some type of bad programmer/computer that is messing something up. (Please let me know if you need any extra details that I might be missing, or photos etc... I know the more detail I give the more helpful it might be, thanks)

Evan
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1991 olds 98 3.8L V6

In all your information you do not tell us anything about your pressures. You may have a restriction but without pressures you don't know.
I have the info on that car if you like. There's a few things that have to work together for that relay to be commanded.

If I can remember correctly, when we were filling it up it was just under 60psi and that was on the low line we were filling up on. We never had the high pressure hooked up. Anything else you need to know? And yes and info about the car would be amazing, appreciate it!

I take it you don't do AC work. Need high and low pressures to have an idea of what's going on.
How long did you evacuate the system and under how much vacuum? Did you take the system apart at all?
I'll get you some info on it in a bit.

We were vacuuming it for 20 minutes and had it down to 27psi on the low line and then after we let it sit for about another 20-30 minutes making sure it would hold, and it seems it does. And we haven't taken the system apart at all, but not sure what that mechanic did behind closed doors when they messed it up/couldn't recharge it.

Didn't know the high side was needed for vacuuming and filling sorry, thought it was just the low side. If there are any videos or websites with instructions that you can recommend I can definitly give that a try!

The system was stagnant for more than a decade. It should had a machine for R12 hooked to it and see what it had. Normally you want to drain the oil out of it before charging with the correct amounts of each. How much oil did you get into the system? I find it amazing that you bought 30lbs of R12. That should have cost you more than a total conversion to 134A.
I have a ton of info on it but we need to do some basics to see where we stand. A scan tool would be great to see what the HVAC unit is doing.
Here's the main part of the electrical for it.
https://cimg0.ibsrv.net/gimg/www.gmf...5f54950709.jpg

The R12 wasn't too expensive, but I'd like to try and keep the system to R12 since I hear it's better cooling and whatnot, except for the environment. But would be open to the idea of r134a if it made this whole process easier lol.
The machine and scan tool I don't have, what are they called? and is it better to bring to a professional to check what the issue is instead of spending however much money the tools are?
For the oil, we didn't drain any out. While we were filling up the system, we filled it up to 2.32lbs of R12 and were going to put in a 4oz can of oil in after as we didn't know quite how much would have been missing, but we first decided to see if the clutch would kick in at all since it was pretty close to full. (Originally to fill it we had the relay jumped, but once we filled it up to the 2.32lbs we tried putting in the relay again to see if the clutch would kick in normally, but no luck so we gave up on the oil as we didn't think it would make the clutch work immediately anyway, and that's when we started checking all the switches). and thank you for the diagram! Whatever you need I can definitely check it out.

I've converted a bunch of vehicles to R134 over the years. It's not a big deal, and doesn't cost a lot. Yes I do agree that R134 doesn't run as cold. There's a consistent difference on every one. The native R134 cars have evaporators designed for R134 which I believe means "slightly larger".

Hey, there was busy with work and other things. Is there a step-by-step test procedure on how to diagnose my problem? Because I can't really give you guys psi numbers because the compressor won't even click on so I can't fill it.

Looking at that diagram you can trace where you problem is. You need a good scan tool or you will be spinning your wheels. Do you understand that diagram?