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A/c compressor won't kick in except on defrost

cameronc

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cameronc Enthusiast

cameronc

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2003 tahoe z71. I can't get a/c to work. I replaced orifice tube and all the seals and took it to get vacuum pulled and charged. The compressor will not kick in on a/c. I can turn it in defrost and it will pull in refrigerant and charge but once you turn it back to max a/c, the compressor won't run. We replaced the high and low pressure switch and the snowflake does light up on climate control. The shop told me my climate control may be bad but everything on it works perfect. It's digital and it switches to all the vents like it should and everything else works on it great. I hate to blow $200 I'm a climate control if it doesn't need it. Any ideas?

cameronc Enthusiast

cameronc

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P.s. I understand the compressor always cycles with defrost, I just stated that because I know I don't have a wiring or power issue because it works as it should when on defrost

Dnt Senior Enthusiast

Dnt

Posted
Posted

So if you jumper the low pressure switch does it run continuously?

Dnt Senior Enthusiast

Dnt

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Posted

OK well just fro grins and giggles jumper the low pressure switch and then take a long handle screwdriver and tap the front of the AC compressor clutch (while running the engine of course) if it kicks in then we have a good diagnosis here.

Supreme Pizza Senior Enthusiast

Supreme Pizza

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Here is what I would do:

 

On the LOW pressure side, use the service port to vent all the pressure out of the system. Then use a Wal-Mart automotive 134A refrigerant refill kit to recharge the system. Before you actually add the refrigerant: start the engine, turn the A/C on, turn the dash temp all the way down, and the blower on hi (full blast A/C). DO NOT do this procedure with the defrost on. Now add the coolant.

 

What you are doing is putting the system through a "pressure cycle". You are going through the entire pressure range of the system. This means that if it has ANYTHING to do with the coolant volume or pressure, it will kick on at some point. Don't be afraid to put 4 or 5 cans of coolant into the system. The system itself consists of a low pressure side, high pressure side, liquid coolant and vaporized coolant, a pump, a clutch, pressure sensors, etc. It can take a lot of coolant and 10-15 minutes of time for it all to get sorted out and balanced inside the system. This whole test will cost about $30, assuming you don't have any of the equipment or tools needed. Cans of coolant are like $4 each. The kit is cheap. Its just a hose with a gauge on it. DON'T buy "A/C Pro" or any of those other expensive ones. Its all the same stuff. Buy the cheapest ones you can get, they work just fine.

 

A/C may seem complicated, but its not. Its a collection of parts, just like a lawn mower engine, or gearbox.

muddkatt Senior Enthusiast

muddkatt

Posted
Posted

 

Don't be afraid to put 4 or 5 cans of coolant into the system.

^^^ Bad Advice.

 

If you chose to empty the system and do a refill, put the correct amount of freon in. On a 2003 Tahoe it requires 25.5 oz for a front air only vehicle and 43 oz if it has front and rear air.

Supreme Pizza Senior Enthusiast

Supreme Pizza

Posted
Posted

If you put too much in, the pump will shut off due to the over pressure. The point is, don't give up on an A/C system after 1 can. If you have a leak in the system, it may take more than the recommended amount of freon to get the system to kick on. Its part of the diagnostic process. Once the issue is resolved, it would be necessary to lower the system pressure to get it back into the proper range.

Dnt Senior Enthusiast

Dnt

Posted
Posted

Never empty out and AC system and recharge without vacuuming the system.. The system will not work properly with air in it.

I suspect a compressor clutch problem and the cycling in defrost was just a coincidence.........

Next test will be for power to the low pressure switch with a voltage meter. Nothing hard here just need a few basic tools and some patience. If the control head is bad it can be verified very easily with a few basic tests.

Heavy 5.7 Enthusiast

Heavy 5.7

Posted
Posted

. If you have a leak in the system, it may take more than the recommended amount of freon to get the system to kick on. Its part of the diagnostic process. Once the issue is resolved, it would be necessary to lower the system pressure to get it back into the proper range.

It's silly to do anything until the leak is found & properly repaired.

Dnt Senior Enthusiast

Dnt

Posted
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LEAK? I thought he said that he had the system vacuumed and recharged? I don't know a lot of times in the evenings I enjoy a few adult beverages and reading this forum, maybe I messed up? Chit I don't know I got to go make a beer run you guys have a great night.................

Supreme Pizza Senior Enthusiast

Supreme Pizza

Posted
Posted

Air in the system will not cause any issues. Repair shops say that in order to get your money. I have never "vacuumed" the air out of any A/C system that I have ever worked on, and they all functioned just fine. My current vehicle needed several A/C repairs when I got it. For instance, one of the hoses was disconnected, so i'm sure there was some air in the system. I fixed everything, and added coolant until the pump kicked on (low pressure switch). Then I kept adding more until the pump kicked off (high pressure switch). Then I bled off some pressure until the pump stayed on at all RPM ranges. Done. Fixed. All you need to do is get the pressure level between the HI and LOW pressure switches, and it will work properly. Air in the system, or a little too much /too little coolant is not an issue. If you go to an A/C shop, they will say i'm totally wrong and that you need to pay them thousands of dollars to fix your air conditioner "properly". My knowledge is based on research and hands on experience. You may disagree with me, but it does not mean that your opinion is correct, or mine for that matter. Stop spending so much time picking apart others people posts, and focus more on helping the person in need.

txab Senior Enthusiast

txab

Posted
Posted

Air in the system will not cause any issues. Repair shops say that in order to get your money. I have never "vacuumed" the air out of any A/C system that I have ever worked on, and they all functioned just fine. My current vehicle needed several A/C repairs when I got it. For instance, one of the hoses was disconnected, so i'm sure there was some air in the system. I fixed everything, and added coolant until the pump kicked on (low pressure switch). Then I kept adding more until the pump kicked off (high pressure switch). Then I bled off some pressure until the pump stayed on at all RPM ranges. Done. Fixed. All you need to do is get the pressure level between the HI and LOW pressure switches, and it will work properly. Air in the system, or a little too much /too little coolant is not an issue. If you go to an A/C shop, they will say i'm totally wrong and that you need to pay them thousands of dollars to fix your air conditioner "properly". My knowledge is based on research and hands on experience. You may disagree with me, but it does not mean that your opinion is correct, or mine for that matter. Stop spending so much time picking apart others people posts, and focus more on helping the person in need.

 

 

 

 

 

Use this poster's advice at your own risk!

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