First, I can say that I have ready the entire stick and search multiple times for the answer to this but had no success.
My A/C compressor shuts off about every 10-15 seconds. I figured it must just be low refrigerant so I purchased a Interdynamics R-134a recharging kit (model #RKR-7). Now the problem I have is when I connect the thing to the low pressure port with the A/C on, the pressure is really high. It gets to the yellow (45-65 psi) section right before the compressor shuts itself off, then it jumps to the red (100 psi) area and when the compressor kicks on again it drops back down, but shuts off before it gets below the yellow.
Now, according to the instructions this means it's either improperly connected to the high pressure side (which it isn't, I've tripple-checked on the forums and many web sites), or it has a huge mechanical problem and I am screwed. However, since the instructions say "make sure A/C is on for at least 3 minutes" I am hoping this doesn't apply.
Basically my question is is it normal for the pressure to be so high with the compressor off? If so, I assume I need to jump out the pressure switch to keep the thing on for a few minutes so I can recharge it?
It'd be great to get a quick answer as I am trying to get the A/C working so I can dry out the inside of my car. I left the sunroof open and it rained
- Ken
'99 Z24, Manual
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My apologies for the typing mistakes, I was in a hurry and forgot you can't edit your posts on JBO forums.
'99 Z24, Manual
Okay typical low iside pressure is ambient temp/2.5, and high side is about 2.5 times ambient temp.
Normaly low side is about 35psi, and high side is about 215psi, as a general spec.
If your pressure drops to low on either side, the compressor will shut off by itself.
You are correct the compressor cycling on and off is most likely low on refridgent. Yes it does need to be on for three minutes ATLEAST before charging it, I usually wait 10, so the pressures can stabilize.
Are you charging the low side as a liquid or a vapor? Thats my first question. Vapor is safest to do.
- 2004 Cavalier - 124k, owned since new
hmmm, this sounds identical to what happened to me.
do this - when you put your a/c on, check if your engine fan is running. its supposed to be on whenever you compressor is on. if its not, check the relay in the engine bay. my relay went bad, and caused the on off on off on off that you get. just one of many possible solutions......
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- Sold my beloved J in April 2010 -
No the compressor does not have to be on however the switch for the AC should be on. The the pressure in the can forces the gas out into the AC pipe. I have done this before, eventually the compressor just turns on.
Be very careful not to over charge your system. You can do it with the A/C on. Since you are not charging an empty system that has be vac'ed down, add small amounts of the 134a at a time. I suggest you set your A/C to max before you start charging.
Okay Viper you got it right, it was the relay for the cooling fan! I never thought to check the cooling fan until I read Rob's comment:
"typical low side pressure is ambient temp/2.5, and high side is about 2.5 times ambient temp."
That's exactly what happens. The reason I was getting high pressure readings on the low side was because the cooling fan wasn't turning on and the high temperature drastically changed the refigerant pressure. It turns out the compressor was shutting off because of high pressure, not low pressure or lack of refrigerant like I initially thought.
I replaced the relay for the cooling fan (the contacts in it were worn down so they wouldn't touch... looks like a surge smoked them as the plastic was a bit molten around one prong). Now it works fine. With the cooling fan keeping the thing from overheating, the low side pressure is down where it should be; about 30 psi. It was 2-3 times this when the cooling fan wasn't working. Temperature makes a HUGE difference.
Thanks guys.
- Ken
'99 Z24, Manual
