How to determine if A/C R134a is low? Checking pressures

[Keven]

Hello,

My A/C fans are not spinning and my A/C compressor is not engaging so I suspect I am low on R134a/Freon. However, when I hook up my gauge to the low side line, either my gauge is broken or I'm not getting a reading. Is there something I am missing?

 

[Votblindub]

The fans should spin regardless of freon being in the system or not. Have you had regular a/c service on the car?

 

[yatzee]

The fans should spin regardless of freon being in the system or not. Have you had regular a/c service on the car?

regular AC service?

 

[Rdsoxx]

http://forums.tdiclub.com/showthread.php?t=242699

 

[Votblindub]

regular AC service?

Yeah, you have to service it at regular intervals. My white car didn't cool down, I thought something broke. I went to a place that does a/c service and they got it to work. I didn't have to replace any parts. They said that the a/c has never been serviced. There are no leaks, nothing is missing, pressure was okay on the high and low end.

 

[yatzee]

Yeah, you have to service it at regular intervals. My white car didn't cool down, I thought something broke. I went to a place that does a/c service and they got it to work. I didn't have to replace any parts. They said that the a/c has never been serviced. There are no leaks, nothing is missing, pressure was okay on the high and low end.

that's a cash grab. I've never heard of nor ever done an AC service. If you have a low freon level, there is a leak. If there is a smell in your vents, there is a product for that.

 

[red16vdub]

Yeah, you have to service it at regular intervals. My white car didn't cool down, I thought something broke. I went to a place that does a/c service and they got it to work. I didn't have to replace any parts. They said that the a/c has never been serviced. There are no leaks, nothing is missing, pressure was okay on the high and low end.

Regular a/c service hahaa. Look at it this way. Your air condition is no different from you're refrigerator which never needs servicing, if it's low there's a leak its that simple.

bajan

 

[hughesjasonk]

turn on the ac and stick a thermometer in the vent or a charge gauge on one of the service ports.

 

[Enabled]

With A/C off, put on manifold gauge and you should have somewhere 100-110 psi in high and low port, depending on outside temperature.

Turn on A/C, and watch the pressures. Low side should drop to ~25-35 psi, and high should go up to 150-250 psi, both depending on outside temperature. The drop in low side and raise in high side should happen fairly quickly, say 10 seconds.

These pressures are not "cast in stone" as they really fluctuate, but should be good enough to see if you have enough R134a.


You never need to add, unless you actually have a leak. Overfilling the system makes it less efficient, and can possibly seize your A/C compressor.

A few things that can result in bad A/C cooling (in somewhat order of likeliness):
-One or both fans not working
-Blend door foam is deteriorated
-A/C compressor weak, or refrigerant control valve needs replacing
-Leak, low R134a
-Blockage, in expansion valve, condenser..
-others

 

[joep1234]

Check your fuses on top of the battery first. They tend to cause the problem of the a/c not working. Last spring I was checking my a/c since it was the first summer coming owning the car. My fuse was corroded and wasn't making contact thus the a/c didn't work. Cleaned things up and the fans worked and the compressor started. Had to add a little Freon but it spit out ice cubes all last summer. Got the Freon at the parts store that had a gauge on it. Total cost was less than $30.

 

[Votblindub]

Regular a/c service hahaa. Look at it this way. Your air condition is no different from you're refrigerator which never needs servicing, if it's low there's a leak its that simple.

bajan

I had them check for leaks and test the low and high pressure. Everything was on point. They said the freon was in there, no parts were missing or broken. It's a good thing I didn't get one of those cans and dump more gas in it, it'd have over-pressurized the system. They hooked it up to the machine that drains the freon and changes it, let it run a bit and now it just works. They said that nobody serviced it before. *shrug* It works fine after that.

 

[Dimitri16V]

there is always some Freon leaking out overtime but not enough to cause the system not to run

 

[Keven]

Hmmm.....looks like I will have to investigate further. I was under the impression that if the car was low on freon the fans/compressor would not engage.

I replaced the clutch 30k ago and filled with r134a then. All the fuses look good but maybe they need to double check.

 

[Keven]

With A/C off, put on manifold gauge and you should have somewhere 100-110 psi in high and low port, depending on outside temperature.

Turn on A/C, and watch the pressures. Low side should drop to ~25-35 psi, and high should go up to 150-250 psi, both depending on outside temperature. The drop in low side and raise in high side should happen fairly quickly, say 10 seconds.

These pressures are not "cast in stone" as they really fluctuate, but should be good enough to see if you have enough R134a.


You never need to add, unless you actually have a leak. Overfilling the system makes it less efficient, and can possibly seize your A/C compressor.

A few things that can result in bad A/C cooling (in somewhat order of likeliness):
-One or both fans not working
-Blend door foam is deteriorated
-A/C compressor weak, or refrigerant control valve needs replacing
-Leak, low R134a
-Blockage, in expansion valve, condenser..
-others

Fans were also replaced around 35k ago. The foam door is definitely deteriorated. I'll look into the rest.

 

[dieselnewbie]

I've been battling problems with my AC for the past year or so and found that my fans did not come on when the freon level was too low. When freon was added they did work (as did the AC) - at least until the level got too low again. Once it gets a little warmer we'll put some dye in the system and track down where this leak is, but the point of this reply was to say that I do believe that if you're too low on freon your fans won't turn.

 

[whitedog]

We are missing info.

What gauges did you hook up? Some cheap ones from HF that have been tossed around in a box or good ones put away safely?
Is there a valve on the coupler that has to be opened?
Did you hook up to the high side?

I h8 AC work and only know a tiny bit so people like enabled are the guys to listen to for specifics, but I think that there is some information missing that will help them help you.

 

[Keven]

I have an A/C gauge...which I've linked below. It's from Advance Auto Parts now I'm wondering if it's broken. I don't remember if it was at 0 when I first tried it but after I hooked it up it was pinned at 100 Psi. It's been working it's way down through the week and currently reads 45 unhooked just sitting in the laundry room. I hooked it up to the low side, it wont fit on the high side.

http://shop.advanceautoparts.com/p/...0-push-and-lock-coupler-ac993-gbm-4/9220016-P

 

[whitedog]

Get or borrow a real gage set.