AC Compressor will not kick in

I replaced my ac compressor, expansion valve, drier, and every single O-ring in the system. I then vacuumed out the system, noticing way too late that the worthless ac gauges I got from autozone do not read vacuum... Anyhow, I figured I would try to charge the system and the low pressure shot way up, compressor never started, thus the high pressure side stayed low. The system was unable to consume a single 12 oz. can and I know it takes approximately 22 oz.

Anyone in here have expertise with automotive AC systems? Here is what the gauges are reading...please excuse the crappy autozone gauges. I do realize they look equalized, but I also may have opened the high pressure valve in my frustration and that's what you're seeing. I know the low pressure side should be reading 21.76-36.26 psi while the high side should read 198.7-227.7 psi.
20210822_140805 by Jose, on Flickr

 

Another thing to note is that my AC button lights up but the idle will not change

 

20210822_152135 by Jose, on Flickr

 

If you don’t trust the gauges, get some of the loaners from oreilly and verify them. They’re a free loan with a deposit.

If you can’t get it to take refrigerant, that says to me that it doesn’t have a proper vacuum. But I’m no expert.

 

No O'reilly's around here unfortunately. I bought these at Autozone because they couldn't find their loaner (their employees are extremely incompetent). It very well could be that I still have a leak somewhere. I think my next step is to add a leak detector and see what happens. Will probably buy another set of gauges as well.

 

Going to buy another set of gauges, return the useless ones, add leak detector, and see what's going on.

 

Did you plug the pressure switch and evap temp sensor back in when you did the expansion valve?

 

https://www.autozone.com/diy/climate-control/how-to-recharge-car-ac

I would try again from the beginning since you said you barely added any refrigerant, then it may be an issue with the pressure switch. According to the link above it should turn on between 20-30PSI on the low side. Double check that you reconnected all wires, could be as simple as that.

 

my 96 had the same issue and what I discovered is that the magnetic clutch pull in coil would pop the 10 amp fuse EVERY time. A 15 amp fuse would work just fine, I discovered this because I ran out of 10 amp fuses. I would start with making sure that you are getting +12 v at the connector to the magnetic clutch first... it could be something as simple as a bad clutch coil.

from the 1996 manual

 

It’s normal to see the pressures equalize when the compressor is not on. Another fact that a lot of people don’t know is that this static pressure should be equal or damn close to the ambient temperature on that given day (with the system at ambient temperature like sitting overnight) …on a properly charged system ( correct amount of refrigerant.)
There is a pressure/temperature relationship most folks don’t know about.
Anyway sounds like your compressor isn’t coming on for one reason or another. I’d start by checking power and ground circuits.
If your compressor is kicking on and off that’s short cycling mostly due to the lack of refrigerant in the system. That is your opportunity to charge the system (with it running) using the low side to help pull the refrigerant into the system. If there’s nothing there to compress, your high pressure will never rise…

 

You should be able to verify if your compressor is engaging by watching the AC compressor. If it isn't coming on check the AC fuse. If the fuse repetitively blows then check the AC Clutch coil. If your AC clutch is good I would go to the other interruptors like High pressure and or temperature/low pressure built into the AC system. They are designed to protect the AC compressor from damage.

 

So, I went out and got some better gauges yesterday. I also checked the fuse and it is not blown.
20210823_085604 by Jose, on Flickr

 

I'm currently allowing the vacuum pump to take the air out of the system and then I will lock the valves so I can see if it actually holds a vacuum.
20210823_120720 by Jose, on Flickr

20210823_120857 by Jose, on Flickr

 

The clutch is not engaging but the AC fuse is not blown. Since neither my old nor the new compressor engage, I can't imagine both clutches to be bad. I will check for voltage at the compressor. I think the low pressure switch will be my next test.

 

I just replaced EVERY AC component on a Honda last Month and did a full charge. You definitely want to verify that you don't have leaks, but it should be accepting the refrigerant in the low pressure side so fast that any leak big enough to keep it from building pressure and causing the compressor to engage should be audible and very obvious. I ran into the same issue where the compressor wouldn't kick on, to transfer refrigerant to the high pressure side. My first troubleshooting was to pull the compressor relay and jump the pins with a wire to try and get the compressor to kick on manually, it did nothing. For me, it was the fuse to the secondary "radiator" fan, I believe it's called the condenser fan. Since it was blown, it wouldn't allow the compressor to kick on. Just another fuse to check.

EDIT: I'm thinking our trucks don't have that relay, must not be electric. Only relevant relay I can find is R11, under the hood, for the AC clutch relay (MG CLT).

EDIT2:...That was for a 2nd gen...more coffee. Just noticed the 1st gen forum title.

 

Did you make sure you plugged the pressure switch and evap temp sensor back in when you did the expansion valve?

 

Check your flyback diode; if that's open then your compressor won't compress.

 

Yes, I forgot to mention this. I just took out the glove box to verify and everything is plugged in.

 

I'm not familiar with the flyback diode, where do I find this?

 

This! Yes, this is exactly what I thought. I vacuumed the system for 30 minutes at noon and shut the valves at 12:30. It's now 1PM and it is holding at 30inHg so I don't think there are any leaks. I'm thinking of charging the system with the pressure switch jumped, but I will check that relay first and see.