99 Silverado A/C in and out....Help!

I have been trying for days now to locate/ fix my A/C issue. I have a

99 Silverado that is not cooling as it should. When it cools, it is fine, it is great. Sometimes it works, sometimes it doesn't. Can't find a common denominator there. Anyway, I HAVE checked the refrigerant and pressure levels are good (45psi). Then I replaced the low pressure switch, no change. It appears that the compressor clutch isn't always engaging. When it spins, the truck is cold and all is well....until it stops. Does this sound like my high pressure switch may be going out or what? What could it be? Thanks in advance.
Reply to
g22dru
Loading thread data ...

45 psi on the low side, clutch engaged, fan set to max, system set to recirculate, temperature control to full cold, is not good, its too high.

Whitelightning

Reply to
Whitelightning

you pressure is probably ok....45 at idle right? Of coarse it would be best to check the high side too. If you havent added freon don't worry about it. Anyway, I would look closely at the compressor clutch. It could be that its not kicking in when its hot. Get a test light and monitor the clutch for 12v. If its got 12 volts to it and its not kicking in its either the connection, ground or bad clutch.

Reply to
ShoeSalesman

you mean the pressure is too high? What would be the next step here? Excuse my ignorance, I haven't dealt with the a/c stuff to much. Thanks for looking!

Reply to
Dru

Correct, 45 @ idle. Great, I will try that this weekend. Thank you very much for the advice! I appreciate it. So the high pressure switch is probably NOT the culprit?

Thanks again.

Reply to
Dru

If you rev the engine up a little you will find the low side pressure will go down. At about 2000 rpm it should be lower, like about 35 (depends on some factors like temp outside, how well the fan works, how worn the compressor is, and of coarse amount of freon. The reason it does this is because the compressor simply works better when you rev it up. This however has nothing to do with your problem unless the low pressure goes too low like 25. If this happens it will kick out for a short time(low pressure switch)till it reaches about 50psi then kicks on again. If this is the case usually it means its low on freon but you really need to see the high side before adding freon (safely). If your

99 has never had freon added before it is most likely low, a loss of a small amount of freon is considered normal. In seven years I would expect it too be VERY low.
Reply to
ShoeSalesman

Not likely, but you need to diagnose it first. (see above) and check back.

Reply to
ShoeSalesman

I will check the 12v on the compressor clutch this weekend as mentioned before, but until then perhaps you could enlighten me on a couple of things.....I bought the refrigerant refill/ lube/ complete kit from Wally world and checked the pressure. That is where it said 45psi and from the illustration, that appeared to be the "full-do not add" zone. Is this different or the same as the amount of freon you mentioned. There has been NO work on the A/C since I bought it new, so I assumed that freon would be needed as well. Also, how might one check the "high side"? I took the kit back and got my 30 bucks back since it appeared to be {?} full. Would that kit be used to check high side too? When we checked it on the 4th it was running fine and the clutch was spinning and all was good. (I couldn't get it to not work) Of course, as soon as I packaged up the kit and took it back, the clutch would not spin and no cold air. Back and forth. Would it have made ANY difference if we were able to have checked it while it was not working properly?

Thanks for all of your help ShoeSalesman. I appreciate your time.

Reply to
Dru

IF it cools well while its working you need to find out why its not kicking the clutch in....back to the test light. Use the test light to check both sides of switches like the low and high ones. When running both wires to the switches should be hot. (current travels THROUGH them). At the clutch one should be hot, one grounded.

Reply to
ShoeSalesman

Dru,

One caution here, the gauge on those kits can be pretty inaccurate, I say this b/c i bought probably about the same thing you did at advance auto a couple months ago, read 0 at first, added two cans, the compressor wouldn't kick on until I got to 55 or so on the gauge, the low side gauges are inaccurate by nature.

NOTE: THE BELOW ADVICE MAY BE DANGEROUS BUT IT WORKED FOR ME!!!

Ignore the gauge, run the truck a/c on when it won't kick the compressor, add freon until the compressor kicks on....this is how I filled mine, been 2 months now and no probs, ice cold a/c.

Again, BE CAREFUL!!!!!!!!

ShoeSalesman wrote:

Reply to
89GMC

what engine do you have if it is the v6, the clutch is probably going out, when the clutch gets hot the magnetic looses it magnetism thats why it work fine when its cold, compressor on gm from 96-99 where not all that great

Reply to
Steven

I have a 2003 silverado with5.3 and the air conditioner cuts in and out when its extreemly hot out. My father has a 2003 2500hd 6.0 and his does the same thing.

Reply to
Jeremy Yeoman

Reply to
CHROME

My 03 Silverado A/C gets warmer and warmer if I just sit still for to long of a time, especially on a really hot day, I mean you'll end up having to turn it off after a while because it'll start blowing out Hot Air, but when I start driving it gets colder and colder again and works really good. When your in a long line in a hot day trying to get into parking at some event, it sucks. I had the A/C compressor take a dump once on me, and it had to be replaced and flushed and recharged like a year after buying the truck. It did it before, it does it now. Is that really how it is? My last truck had no A/C, but I can't remember a time is someone else's car doing this either.

Reply to
JBDragon

I live in Texas where it's hot as hell. I had the same problem that you have with every GM vehicle I ever bought. I'm really not saying this to bash GM but I bought my first Dodge Ram back in 2001 and I haven't looked back. Ice cold air and no mechanical problems at all. Not even the vibration that my 2000 Shakerado had.

Bob

Reply to
Bob M

I'm not a big fan of Dodge Trucks. They have there own problems. I haven't had any AC problems in a couple years, but when it's really HOT out and I'm just sitting there, the AC Temp gets less and less cool and will actually start blowing out warm air. Once I'm moving again it starts getting cold once again, and it does get quite cool. This is the first Vehicle I've had with AC! My last 77 Chevy truck, NO AC, my Old car I had, No AC. My Parents Cars/Trucks never had AC when I was growing up. The only AC that was around was a small Unit in my Parents Bedroom because my Dad worked Graveyard, so slept during the day. It's almost like the fan is not pulling enough Air though the Condenser when I'm just sitting there, yet the Engine doesn't over heat. Just don't know if this is normal, or if I should just bring it to the dealer and have them take a look at it again. It's normally not a problem, but last year for example waiting behind a huge line of cars to get into the State Fair, it was pretty HOT out, and I'm sitting there cool, and after a bit, it's getting less and less cool, until it's blowing out HOT Air. I hat to turn it OFF and Open the Windows. What's the point of having AC if it's not going to work. No AC, in a Hot truck sitting there waiting for the line to move up, very very slowly wondering where the FU*K is my AC. Other then the AC, it's been a great truck.

Reply to
JBDragon

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.