Auto A/C problem... 'tis the season, eh? lol

[tRidiot]

That is the accumulator/dryer. Dripping is probably from the evap coil and is normal. Really the only way to start knowing what is going on is to put gauges on it. At least on the low side. Start the truck and turn the AC on full blast and recirculate. See if the compressor is cycling on and off. Should be easy to tell. Then have someone rev it up to about 2k RPM and see if it cycles on and off. cycling in either situation cold mean low charge. What year is the tahoe? If it is the GMT400 like my truck, you've probably got a belly leaking compressor. Very common and a pretty easy fix if you've got a couple hundered and a couple hours.

You might have a problem with your fan if it is warming up at stop lights. If the compressed freon isn't getting cooled into a liquid by the condenser it will get warm.

I've replaced my stock fan with electric ones. They seem to be working fine, they come on when the motor is hot or when the compressor is running. Compressor doesn't seem to be cycling, it works "ok" when at highway speed. I may try HMFIC's advice... gives me an excuse to buy a set of gauges.

Although, I found this:

AIR CONDITIONER PROBLEM: INTERMITTENT COOLING

An A/C system that blows cold air for awhile then warm air is probably freezing up. This can be caused by air and moisture in the system that allows ice to form and block the orifice tube.

Evacuating the system with a vacuum pump will purge it of unwanted air and moisture. Evacuation should be done with a vacuum pump that is capable of achieving and holding a high vacuum (29 inches) for at least 30 to 45 minutes.

For best performance, an A/C system should contain less than 2% air by weight. For every 1% increase in the amount of air that displaces refrigerant in the system, there will be a corresponding drop of about one degree in cooling performance. More than 6% air can cause a very noticeable drop in cooling performance, and possibly cause evaporator freeze-up.

Air can get inside a system through leaks, by not evacuating the system prior to recharging it, and/or by recharging the system with refrigerant that is contaminated with air. Recovery equipment can suck air into the recycling tank if an A/C system contains air or if the system has a leak. For this reason, the refrigerant recovery tank on recycling equipment must be checked and purged daily. On some equipment, this is done automatically. But on equipment that lacks an automatic purge cycle, tank pressure and temperature has to be measured and compared to a static pressure reference chart.

Some refrigerant identifier equipment can detect air in the system as well as other contaminants. An identifier should be used to check the refrigerant before the system is serviced to prevent cross-contamination of recovery and recycling equipment.

I DID have one incident a couple of weeks ago where I was going to Tulsa and the driver's side started blowing HOT air while the passenger's side was blowing cold (independent climate control)... turning it on/off didn't help, adjusting temp didn't help. I eventually just killed the truck and restarted it at a stoplight and everything was peachy afterwards. WEIRD. Hasn't happened that way since...

Reading the info above, I could be low on refrigerant AND have some air in the system if I have a leak. It would explain some of my problems.... truck is a 2004 Chevy Tahoe 5.3L.

 

[338Shooter]

I wouldn't think you'd have air in the system. Air isn't going to get into a system that is pressurized very quickly. Especially not 2% by weight. Sounds like you might have a controller problem too.

 

[MBowman325]

There's a low pressure switch, so the compressor will run, suck down the refridgerant, and when it gets to a low point, the switch will open and the compressor will stop for a few minutes. If you're low, you'll hit that point quicker. A quick visual test of turning it on and then watching the clutch engage / disengage will tell a little bit. If it cycles quickly then waits a while before it cycles again, I'd suspect that. You can also feel the lines (do not grab them!) and that'll tell you if you're low or not. I always have to refer back to the Internet to remember what that actually tells you though.

If you have a FSM for yout truck, it'll tell you details on the AC charge. if I still had the FSMs for my Impala, I could give you ball park figures...

 

[Hump66]

If you give me the year/model/engine etc. I can get on Mitchell and look up the specs for you.

 

[nich018]

Years ago, I used to put freon in myself. But it's all changed since then. As far as freon goes. Every summer I would add a can or two.

 

[inactive]

If it gets cool eventually, like you say, I'd chalk it up to being low on freon coupled with 110+ temps. More serious problems end up with the system blowing hot all the time.

Seriously, get a can of freon with the equipment bundled. It's super easy.

 

[okievarmint]

Also, check your cabin air filters. The musty smell may be caused by condensate build-up on the evaporator core, GM TSB99-01-39-004C touches on this.
Earl

 

[tRidiot]

Well, I just went to Advance and spent $50 to get a kit with a coupler, gauge and 2 large cans of R-134a with leak sealer and an ultaviolet leak detector built-in. Also comes with a UV light pen to search for leaks. I'll give it a shot later and see where my pressures are and how much 134 I need.

I'll update back with results. It may be the morning before it's cool enough, though, being as how it's 111F outside!

 

[HiPower]

You'll be sorry you added the leak sealer - it's gonna cost you more money to fix the problems it will cause.

Something I've never understood...if you have a refrigerant leak, you also have an oil leak. The oil in an A/C system circulates with the refrigerant, but nobody ever adds oil until their compressor dies.

 

[tRidiot]

You'll be sorry you added the leak sealer - it's gonna cost you more money to fix the problems it will cause.

Something I've never understood...if you have a refrigerant leak, you also have an oil leak. The oil in an A/C system circulates with the refrigerant, but nobody ever adds oil until their compressor dies.

I really did consider oil, but I don't know how much to add. Do you add a full can? Actually, I'm thinking the one I got may have oil in it, too... lemme go check.


<edit> Ok, here's the kit I got. No oil in it, but I haven't opened it yet. I can take it back and get something else, or add oil to it, if I knew which of the three R134a oils to add. I'll look into that.

Why do you say I'll be sorry about the leak sealant? Because by itself it causes more problems, or did you mean without adding oil, too? I want to do this right if possible, short of going to an A/C repair shop. If I need to have the system rebuilt, I will, but I'd like to try to fix it on the cheap if I can, as long as I'm not going to cause major problems down the road. Tell me about your experience level with this stuff.