Automotive Air Conditioning Information Forum

Ok I just replaced compressor because ac would not hold freon. Evacuated the system and went to charge, freon was going in and finally compressor starts to click on and off very rapidly, the system finally stopped taking freon at about 1 can but the low side is at 90-100 psi while high side is at 150ish, and is just clicking on and off simultaneously! Seems like it's not compressing? I'm guessing maybe drier or orfice clogged because it had trouble taking that 1 can. I would try jumping the compressor but I'm not sure which sensor, there 2 on the compressor and 1 on the hardline right beside compressor. Any help on troubleshooting would be greatly appreciated

One can is 12 ounces- your truck holds 2 lb or 32 ounces- so you need almost 3 cans. You have trouble getting the first can all in because it is almost empty- put another can on, then another and be happy. The compressor will suck refrigerant in and stop cycling so rapidly when you get enough "freon" as you call it in.

The thing is, I couldn't even get all of the first can in, because the low side pressure is at a 100 psi! Is it normal for liw psi to be that high on 1can?

Salteedogg54 wrote:The thing is, I couldn't even get all of the first can in, because the low side pressure is at a 100 psi! Is it normal for low psi to be that high on 1can?

Could be just the static pressure that you're reading because the compressor hasn't yet kicked in.

Ok guys think I found the fix, I went ahead and put a new drier and orphice tube (old tube was gummed up!) and now the truck pulled the refrigerant right in, can got cold and sucked dry pretty quick unlike my first attempt! What psi should it run at on low side? 2 cans got it at 40 psi, I added a little more out of a third can and stopped at 45 psi. This was in 90° weather. It's blowing cold as of now!

I hope you pull adequate vacuum first--and you always charge by weight- not pressures in automotive a/c....so don't ask for pressure specs- there are none...just opinions

GM Tech wrote:I hope you pull adequate vacuum first--and you always charge by weight- not pressures in automotive a/c....so don't ask for pressure specs- there are none...just opinions

And pressures are less helpful anyway if not measured at appropriate rpm like (1800 rpm) with system running at that rpm a couple of minutes. And pressures are less helpful without real service gauge kit and readings of high side too.

In your first post you said the reason you replaced the compressor was because it wouldn't hold refrigerant; if your orifice tube was clogged I bet your AC performance was crappy then too !!! And if your refrigerant did all leak out, would've been wise then to replace the accumulator then too (I realize that the 1994 GM accumulator is a crappy thread design though).

Original compressor was leaking freon straight out of the compressor instantly so it has never even worked at all. Yes I vacuumed it for 45 minutes straight, was sucked down to 27 in hg, let it sit for 30 minutes and vacume never leaked. I put 8 ounces of oil in compressor before assembly, plus 2 and half cans after vacume. I wasn't sure on the exact amount as I read conflicting specs from multiple sights. Quick question though, if it calls for 2lbs (32ounces) and I put 1-1/2 lbs in and I'm already at 45psi, it's ok to add more? I just don't want to blow an o ring out!

Salteedogg54 wrote:Original compressor was leaking freon straight out of the compressor instantly so it has never even worked at all. Yes I vacuumed it for 45 minutes straight, was sucked down to 27 in hg, let it sit for 30 minutes and vacume never leaked. I put 8 ounces of oil in compressor before assembly, plus 2 and half cans after vacume. I wasn't sure on the exact amount as I read conflicting specs from multiple sights. Quick question though, if it calls for 2lbs (32ounces) and I put 1-1/2 lbs in and I'm already at 45psi, it's ok to add more? I just don't want to blow an o ring out!

Saltee - that's one reason you need to read high pressures too; loaner gauge sets are available at Autozone.

Questions:
1. That 45 psi is at what rpm?

2. For that reading, did you have a fan blowing at the front grille/condenser ?

3. You said you put in 1-1/2 lbs: that's 24 oz. unless you mean a can and a half which would be 18 oz. as the cans are 12 oz each. So either way you're less than 32 oz. It's important to add the correct amount of refrigerant, for both oiling and operational cooling.

System has roughly 26-28 ounces of freon, I didn't mean 1-1/2 lbs. I added 2 cans plus a little out of a third can and stopped their since it was at 45 psi. 45 psi at idle, no fan blowing, just the mechanical fan. I have ac gauges, high side was 250ish psi.