A/C question?

[steelydan]

My 1999 Sub...the A/C works but not like it should. Pressure on the low side is too high with compressor running. It is into the red on my A/C guage. What should I check?

 

[THEFERMANATOR]

You need to know what the pressures actually are. Those cheap guages that come on top of a can are not wort a crap for charging an A/C system.

 

[iviper123]

too much 134? in the system

 

[steelydan]

You need to know what the pressures actually are. Those cheap guages that come on top of a can are not wort a crap for charging an A/C system.

Unfortunately all I have. System had higher than reccomended pressure on the cheapo guage...but it was working a bit. It is unseasonably hot where I was working (Seattle 105`) and the a/c just quit today. Compressor not running, checked pressure again with the cheapo and it was too low. Added some cheopo r134 that you cannot buy in Canada...and got pressure back up to blue on the cheapo guage. Still no A/C although the compressor is now running. Suggestions?

 

[Odlaw]

You need to get some real gauges to properly troubleshoot your system - you can get a decent set from any auto parts store or Harbor Freight for less than $50.00. If you can't get them or don't feel comfortable using them, your ole gal is gonna have to visit an A/C shop.

If you were showing high before, and now it's low and compressor is not engaging, it sounds to me like you have a leak somewhere. You can look for oil on the A/C lines or on the condensor - that will be a dead givaway of a leak. Check the high side shrader valve. If you charged it back up enough to get the cheapo gauge in the blue and still not blowing cold it could just need more refridgerant.

It's really difficult to fully troubleshoot these types of problems without gauges.

Good luck, I feel for you - my A/C was dead a couple months ago.

Smitty

 

[figment]

Unfortunately all I have. System had higher than reccomended pressure on the cheapo guage...but it was working a bit. It is unseasonably hot where I was working (Seattle 105`) and the a/c just quit today. Compressor not running, checked pressure again with the cheapo and it was too low. Added some cheopo r134 that you cannot buy in Canada...and got pressure back up to blue on the cheapo guage. Still no A/C although the compressor is now running. Suggestions?

I can get the r134 in the little cans at the local Peavey Mart chain, I live in SK. I over charged mine and blew out the seal behind the clutch on the compressor, got fed up and paid $300.00 to have it fixed. Never doing it myself again.

 

[mitchedo]

You need gauges or you need to take it to a shop. Plain and simple. I took my old Suburban in to get a compressor replaced. AC was fine, but the compressor had just started making some noise. To make a long and sordid story short, I paid this company $800 and they utterly destroyed my AC system. I bit the bullet, got some books, a vacuum pump, and some gauges, and now I fix my own AC.

The best way to charge these systems, and the way I charged mine, is by weight. If you still have a functioning system, then you can charge by temperature and high-side pressure. Low side pressure tells you if you have a functioning system, but it can't tell you how much to put in. You MUST have a high side pressure reading to charge by pressure.

Harbor Freight sells gauges for a reasonable price. You need to get a book put out by Mastercool about how the systems work and how to troubleshoot them.

I think it should be okay to post a link to a really helpful AC forum. It's run by the guy who sells the parts, but he went above and beyond to treat me right. It's ACkits.com

Don't go there and post this same question or you'll get the same answers you've been getting here. Get some gauges and a thermometer and take some measurements. Then go ask your questions.

Some typical reasons for your low side pressure being too high is either there is too much charge in it, or your compressor is too weak, or your condenser isn't getting enough air through it. ...but you need the high side measurement to diagnose. In my case, I didn't realize the orifice tube was in the condenser when I changed out the condenser. I put it all back together without an orifice tube. :mad2: My low side pressure was too high.

 

[mitchedo]

Unfortunately all I have. System had higher than reccomended pressure on the cheapo guage...but it was working a bit. It is unseasonably hot where I was working (Seattle 105`) and the a/c just quit today. Compressor not running, checked pressure again with the cheapo and it was too low. Added some cheopo r134 that you cannot buy in Canada...and got pressure back up to blue on the cheapo guage. Still no A/C although the compressor is now running. Suggestions?

Low pressure, compressor not running, usually is due to extremely low (or no) charge (and air in the system). Charging until low side pressure is in the "blue" (whatever that is), then seeing the compressor coming on (and short-cycling) would indicate you added enough 134 to engage the compressor. You probably would need a total of a pound and a half or so, but that's only a wild guess, and you need the high side pressure reading to know how much to put in. Actually, if the compressor was not running, and you still got a low reading, and it's hot outside, it sounds like your system may well have been completely empty, which means it has air in it. If it has air in it, it has moisture in it. If it has moisture in it, it won't work.

If there was any freon at all in the system, and the compressor was not running, you should have seen the pressure on your gauge being too high. I don't have a P/T chart handy, but it will be about 60 psi if there is any charge at all in there and the compressor isn't turning. It needs to run more like 25-30 psi in order to cool, and will only be low if the compressor is working (or the system is empty). Once you get air in the system, you need to find the leak, probably flush, definitely change the drier, dig out the O-tube and look for gunk on it -- then diagnose and repair.

My guess (from limited information) is that the system was completely empty, got air and moisture in it, and needs to be evacuated and recharged (after the leak is fixed).

This guess is based on the following:
1. low side pressure too low, compressor not turning -- no charge
1a. This also means you probably have air (moisture) in the system.
2. low side pressure too high after adding 1 can, compressor turning -- weak compressor and/or moisture in system
2a. you need to pull the orifice tube and see how much gunk is on it.
2b. you need to evacuate the sytem and pull a good vacuum before recharging.
2c. you might need a new compressor

If you have rear air, that makes things even more fun to diagnose. You need high-side readings.

 

[jmiller]

mitchedo,
great explination of A/C toubleshooting. :thumbsup: :thumbsup: :thumbsup:

reminds me of my Linclon Tech days.