Trying to fix my mom's Altima ac problem here. What's the trick to add the refrigerant from a zero pressure system? The compressor was working recently but after having the system evacuated and vacuuming the system with my vacuum pump and manifold gauge set the compressor clutch will not engage. I've see tricks to jump the compressor or shunt the low-pressure switch but those seem a little sketchy. I read someone also use an A/C Pro canned air system but I'm not sure if that is pressurized enough to get the compressor to engage. Any suggestions?
I really appreciate it!
Thank you so much!
Mark in Florida
Your system should be under vacuum so the A/C compressor clutch doesn't need to engage for you to be able to begin charging the system. Once enough refrigerant is in there, the AC clutch will engage.
Make sure you read the A/C capacity sticker under the hood. That Nissan probably doesn't take much more than 18 ounces. (1 1/2 cans). So, don't overfill the system. Get an ounce scale.
Also, purge the air out of that center yellow hose on the manifold gauge by loosening its connection at the manifold a little until refrigerant starts coming out, then tighten it and open the low side valve on the manifold gauge.
Hi Jack! Thank you for your help. Good news & bad news here. You were 100% right on. Turned out my yellow hose was on the manifold a bit too tight. I loosened it and saw the pressure gauge kick up real quick. So I got it fully charged to 17.5oz of R134. But it still blows hot. The compressor does kick on so I'm not sure what it could be at this point. If I knew for certain it was a faulty compressor and that's all it was, I'd probably do it myself but I'm considering taking it to a mechanic at this point. Any other suggestions?
Btw...that is exactly the video I was watching while I was doing this. ChrisFix did a good job on that video.
Thank you,
Mark
Now that's it's charged with the correct amount of refrigerant what are the system pressures?
I just did a 2005 Altima about a month ago that the cooling fans weren't coming on when the AC was turned on. Replaced the fans and the AC worked great.
If you still have those AC gauges hook them back up. The pressures will give you a hint as to what's going on. If you need some suggestions, come back with the pressures.
Google a R134a Temperature Chart and compare your pressures with your ambient air temperature.
Scotty did a video on interpreting the high/low pressures.
You may find it useful in interpreting your pressures.
(Incidentally, that Altima performs a pretty neat Self IPDM test which you may find useful in the future. Easy way to tell if the A/C clutch and Cooling fans are working, among a few other things.
Google: Self Diagnostic Mode on Nissan Altima.)
HEEEEEERE'S SCOTTY
https://www.youtube.com/watch?v=80jSH8VQZms
Thank you so much for the pointers guys. My pressures after the recharge are 35psi on the low side and 60psi on the high side. My guess is bad compressor. But whats the chance it might need compressor, drier, etc. etc.? Should I attempt to replace only the compressor if ya'll agree it's a bad compressor? Thanks again.
FYI....the outside temp was about 93F here in Florida (high humidity). I also confirmed the compressor engaged (heard it turn on) and saw it spinning.
Could be an internal compressor leak, but an expansion valve stuck open can also cause the high pressure to be too low (too much refrigerant flowing into the evaporator). That is usually accompanied though by higher than normal pressure on the low side.
If you do replace the compressor, at a minimum the drier should also be replaced. You'll probably find it to be required for the compressor warranty.