A/C problems, need suggestions...
03-12-2012, 11:37 AM
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A/C problems, need suggestions...
So my A/C went out in my 2003 Tahoe and I am trying to diagnose what is broken before the weather gets hot.
Currently, the compressor won't kick on when I press the A/C button or the Recycle Air button, but the fan speed works fine, it's just ambient air that comes out. I jumped the low pressure sensor with a wire, and it still didn't come on. The belt on the compressor is spinning, but the clutch just won't engage. Checked the A/C fuse already, are there others I should check?
I already have another compressor I picked up for cheap, but I would rather not replace it if that's not the problem.
Thoughts of ways I can diagnose this myself?
Currently, the compressor won't kick on when I press the A/C button or the Recycle Air button, but the fan speed works fine, it's just ambient air that comes out. I jumped the low pressure sensor with a wire, and it still didn't come on. The belt on the compressor is spinning, but the clutch just won't engage. Checked the A/C fuse already, are there others I should check?
I already have another compressor I picked up for cheap, but I would rather not replace it if that's not the problem.
Thoughts of ways I can diagnose this myself?
03-12-2012, 04:21 PM
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I have not. But I jumped the low pressure switch, so if the pressure was low, the compressor would still kick on. I was told this is how you could rule out being low on freon or a faulty low pressure switch. Is that true?
03-13-2012, 10:01 AM
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I'm probably going to have to do that either way, so I might as well learn now.
03-13-2012, 03:33 PM
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03-13-2012, 03:50 PM
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Interesting, thanks for the link.
A friend suggested I put a voltage meter on the harness to see if I am getting any voltage to trigger the compressor clutch to engage. If so, the compressor is shot, if not, something upstream is not sending the signal.
A friend suggested I put a voltage meter on the harness to see if I am getting any voltage to trigger the compressor clutch to engage. If so, the compressor is shot, if not, something upstream is not sending the signal.
03-13-2012, 05:15 PM
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I just remembered that I switched out the A/C relay with a relay that I was sure worked (fuel pump iirc) and no change. Would that be the same as testing the voltage at the pigtail and narrow my problem down to the compressor itself?
03-13-2012, 09:01 PM
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The compressor should get a signal only if refrigerant is fully charged, so you could be fooled if refrigerant is low.
03-14-2012, 09:58 AM
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To avoid that, I could jump the low pressure sensor again while testing for voltage, correct?
But this weekend, I am going to try to get some gauges on it, and next week I am going to get with my tuner to have him scan it for codes and command the compressor on. Hopefully all of this gets me somewhere, fingers crossed.
Last time my A/C went out in 2006, I just took it to the dealer. That mistake cost me $800 and it didn't even involve replacing the compressor. Not doing that again.
But this weekend, I am going to try to get some gauges on it, and next week I am going to get with my tuner to have him scan it for codes and command the compressor on. Hopefully all of this gets me somewhere, fingers crossed.
Last time my A/C went out in 2006, I just took it to the dealer. That mistake cost me $800 and it didn't even involve replacing the compressor. Not doing that again.
Last edited by TX Tahoe Z71; 03-14-2012 at 10:01 AM.
03-14-2012, 10:22 AM
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I believe that assumption is correct.
It looks like you have a good plan. I use a local shop (advertises in the church bulletin) who takes on things that are too time consuming, require tools that I don't want to buy for a one-time use, or are very messy. The cost for most jobs is reasonable. However, I am a bit more cautious for higher-end vehicles and have gone to the dealership for certain things. Finding and using the right place/person (including yourself at times) is the key to getting the job done right.
It looks like you have a good plan. I use a local shop (advertises in the church bulletin) who takes on things that are too time consuming, require tools that I don't want to buy for a one-time use, or are very messy. The cost for most jobs is reasonable. However, I am a bit more cautious for higher-end vehicles and have gone to the dealership for certain things. Finding and using the right place/person (including yourself at times) is the key to getting the job done right.
03-14-2012, 12:41 PM
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I need to find a place like that. I have a good place for general mechanic stuff that I don't want to or have time to tackle, but he doesn't really do specialized stuff, like transmissions, a/c and chasing electrical gremlins.
03-14-2012, 03:15 PM
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Close to the small shop I referred to is a well-known auto-electric shop. If those guys can't solve the electrical problem,no one can. dealerships that are stumped bring their customer cars to these guys. They worked on my 68, many years ago.
03-22-2012, 01:27 PM
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So tested it with a multimeter after bridging the low pressure sensor pigtail and bringing the truck to operating temp. No voltage coming from the pigtail going to the compressor. Tested the multimeter on other things, worked fine. Checked all of the compressor and HVAC related fuses and they all check out. What is the next step? Should I bring a wire from the battery to the compressor to see if it fires up? What are the likely points of failure? Is there a way to test the a/c control panel inside the truck?
But there is no continuity from the low pressure sensor, so does that mean the system has low pressure?
But there is no continuity from the low pressure sensor, so does that mean the system has low pressure?
03-22-2012, 03:09 PM
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When I looked at this statement from the link:
I think getting a recharge may be your best bet.
There is only one method to determine refrigerant charge.....recover and measure/weigh the amount recovered. Then evacuate the system for app. 15-20 minutes and recharge to OE specifications utilizing the correct recharge equipment. A can of refrigerant and a hose with a $.25 gauge is not going to accomplish this. Service the system correctly....keep screwing around with jumping this and jumping that....and operating the system with a undercharge and a good bet is that you will be spending some serious cash on new parts.....heck, this will occur if the system is not totally recharged.....undercharge this system several ounces and the compressor will suffer serious damage due to lack of lubricant movement.
Static pressures are not an indication of the amount of refrigerant within the system. At any given temperature a 12 oz can has the same pressure as a 30 lb cylinder. It is a temperature/pressure thing...
Adding one can or a parcel charge of one can should be sufficient to activate the compressor...unless there is a problem in the electrical supply to the coil. Be careful attaching 12 volts directly to the compressor....some of these Denso units have a built in diode in the coil and may be damaged.
Static pressures are not an indication of the amount of refrigerant within the system. At any given temperature a 12 oz can has the same pressure as a 30 lb cylinder. It is a temperature/pressure thing...
Adding one can or a parcel charge of one can should be sufficient to activate the compressor...unless there is a problem in the electrical supply to the coil. Be careful attaching 12 volts directly to the compressor....some of these Denso units have a built in diode in the coil and may be damaged.
03-22-2012, 04:03 PM
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Yeah, I've pretty much come to that conclusion too. Looking around for good places in Houston right now. Thought I would be able to diagnose it as the compressor, have a shop discharge it, install new compressor and recharge. But that would have been too easy 
04-16-2012, 11:08 AM
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So turned out it was out of refrigerant. Spoke with the mechanic and apparently there are two low pressure switches, so jumping just the one didn't work to bypass it. Quick recharge and I was on my way... however it has been a bit over a week and it no longer blows cold. Luckily they put dye in it and told me to bring it back if it doesn't stay cold. So heading back over to find the leak sometime this week. But at least it has been diagnosed.
04-16-2012, 11:05 PM
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Generally, if you lose refrigerant, even after 9 years, there's probably a leak. My 01 C5 still blows ice-cold air. Let's hope the leak is easy to access and fix.
04-17-2012, 08:32 PM
#20
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I am very good friends with one of the service managers at a local dealer - one of the only GM elite dealers in Houston. Ping me a PM. They will help you diagnose and fix on your own if you wish.