Intermittent A/C issue related to voltmeter gage change?

[KATfishing]

2008 Yukon Denali, 6.2L, 181K miles. Original A/C components and alternator. Newer battery.
On hot days my A/C has intermittently quit working while driving. When it happens I always notice the volt gage displaying its lower level as seen in second pic. In first pic (above 14), the AC is usually working. When it quits working, I can shut off the vehicle at my next stop and it always "resets" and is working again. Sometimes, it'll begin working again while driving and during those times I notice the gage has returned to 14+. I am not a mechanic, but I've learned a lot from this forum, sometimes just by asking a few simple questions that help point me in the right direction as to whether its a DIY job or take it to the professionals. Think the gage correlation is purely coincidental? Or, might this be related to the electrical system... perhaps alternator? The alternator is original, but there haven't been any typical signs of it failing (i.e. dimming dash lights/headlights, or error lights). Vehicle starts strong every time. Or is it more likely a failing compressor, or something else in the AC system? So far, it keeps coming back ice cold, but when it goes out it's completely warm. My snowflake button to activate the AC stays fully lit whether it's working or not. Thanks for any thoughts.

 

[Doubeleive]

well supposedly when the ac is going the voltage is supposed to in a charge mode, the RVC (regulated voltage control) will not charge the battery if it detects there is a enough charge to run everything without needing additional power, ac of course is a big drain so what you are seeing is normal voltage wise.
you may want to have the ac system checked to be sure it is fully charged for starters and go from there. if the r12 or whatever they use now is low it can make the system be intermittent, but so can some other things but I would start with the ac charge test first.

 

[Foggy]

The electric fans take quite a bit of power... So maybe your fans are weak or
your alternator is not good enough to keep the fans going at the proper speeds

 

[Geotrash]

Next time it happens, before you shut the car off, pop the hood and take a look at the air conditioning compressor. What you’re looking for is whether or not the clutch is engaging the compressor or not. I’m guessing that your air conditioning compressor clutch is starting to fail requiring more voltage than is available when the alternator is in no charge mode to function.

 

[BG1988]

2008 Yukon Denali, 6.2L, 181K miles. Original A/C components and alternator. Newer battery.
On hot days my A/C has intermittently quit working while driving. When it happens I always notice the volt gage displaying its lower level as seen in second pic. In first pic (above 14), the AC is usually working. When it quits working, I can shut off the vehicle at my next stop and it always "resets" and is working again. Sometimes, it'll begin working again while driving and during those times I notice the gage has returned to 14+. I am not a mechanic, but I've learned a lot from this forum, sometimes just by asking a few simple questions that help point me in the right direction as to whether its a DIY job or take it to the professionals. Think the gage correlation is purely coincidental? Or, might this be related to the electrical system... perhaps alternator? The alternator is original, but there haven't been any typical signs of it failing (i.e. dimming dash lights/headlights, or error lights). Vehicle starts strong every time. Or is it more likely a failing compressor, or something else in the AC system? So far, it keeps coming back ice cold, but when it goes out it's completely warm. My snowflake button to activate the AC stays fully lit whether it's working or not. Thanks for any thoughts.

the current sensor could be bad this is part of the charging circuit..


if it is the clutch just replace the clutch don't replace the whole compressor


it would be hard to trust a remanufatured or new one as now days the quality is poor

 

[Denali Deen]

My a/c has been doing the same for a couple of years and have not been able to track it down. I replaced the compressor and it seemed better for a short time then back to the same thing. Then did the expansion tank and was a little better but again back to the same thing. Over the winter my alternator started acting up getting a discharge warning while driving. I finally put a new alternator in and a/c has not been cutting out like it used to. Not sure that it is officially fixed but has been better after the alternator

 

[KATfishing]

My a/c has been doing the same for a couple of years and have not been able to track it down. I replaced the compressor and it seemed better for a short time then back to the same thing. Then did the expansion tank and was a little better but again back to the same thing. Over the winter my alternator started acting up getting a discharge warning while driving. I finally put a new alternator in and a/c has not been cutting out like it used to. Not sure that it is officially fixed but has been better after the alternator

Thanks for sharing this info. It has been pretty consistent with the symptoms. When starting the vehicle, the A/C comes on ice cold with the volt gauge showing the higher level (above 14). As soon as the gauge drops to the lower level, within a short time the air quits working. Ironically, I can pull over, shut the vehicle off, immediately turn it back on, and A/C blows ice cold... when turning vehicle back on, volt gauge goes right back to 14+. Think Auto Zone, or another auto parts store, could accurately determine if the alternator is not working properly with the battery/alternator tester device? Yesterday, I went to turn the key, and nothing. Turned it again, and nothing. Turned it a third time and it started strong, but briefly displayed a "Service Vehicle Deterrent System"... it went away once the vehicle started and has been fine on a few trips. Some strange things are beginning to happen at 182K.

 

[KATfishing]

Next time it happens, before you shut the car off, pop the hood and take a look at the air conditioning compressor. What you’re looking for is whether or not the clutch is engaging the compressor or not. I’m guessing that your air conditioning compressor clutch is starting to fail requiring more voltage than is available when the alternator is in no charge mode to function.

Thanks for sharing this info. It has been pretty consistent with the symptoms. When starting the vehicle, the A/C comes on ice cold with the volt gauge showing the higher level (above 14). As soon as the gauge drops to the lower level, within a short time the air quits working. Ironically, I can pull over, shut the vehicle off, immediately turn it back on, and A/C blows ice cold... when turning vehicle back on, volt gauge goes right back to 14+. Given this, do you think that would be symptomatic of the clutch going bad? It's odd that I can get the A/C immediately back when restarting the vehicle, but maybe it only is working when the alternator is in charge mode. I thought the alternator would stay in charge mode based on load/demand. I don't recall seeing the gauge drop like that when it's under load in the past. I keep suspecting the alternator, but the vehicle starts well and doesn't seem to display other tell-tale symptoms of bad alternator, but wondering if an auto parts store can accurately test it at least to rule it out.

 

[Geotrash]

Thanks for sharing this info. It has been pretty consistent with the symptoms. When starting the vehicle, the A/C comes on ice cold with the volt gauge showing the higher level (above 14). As soon as the gauge drops to the lower level, within a short time the air quits working. Ironically, I can pull over, shut the vehicle off, immediately turn it back on, and A/C blows ice cold... when turning vehicle back on, volt gauge goes right back to 14+. Given this, do you think that would be symptomatic of the clutch going bad? It's odd that I can get the A/C immediately back when restarting the vehicle, but maybe it only is working when the alternator is in charge mode. I thought the alternator would stay in charge mode based on load/demand. I don't recall seeing the gauge drop like that when it's under load in the past. I keep suspecting the alternator, but the vehicle starts well and doesn't seem to display other tell-tale symptoms of bad alternator, but wondering if an auto parts store can accurately test it at least to rule it out.

It's also possible that the battery itself is falling back to a lower voltage than it should when the system shuts the charging system off to save fuel, as Wes mentions above. You might have the battery tested at Autozone to see what it's falling back to.

 

[KATfishing]

Just reporting back to this thread on my progress. I ended up pulling the alternator and took it to O'Reilly's for a bench test. It passed the test, but was definitely on the weaker side, so with 182K on it, I decided to replace it. Installed the new one and took it for a nice 45-minute ride. The volt gauge was noticeably higher, and never went into that low maintenance mode as it kept doing on other rides. The A/C stayed on blowing cold for the entire time. However, the next day I took it for a longer ride and it cut out again when volts dropped back. Today, I had battery tested and it passed as good and strong. Also, I put a gauge on the A/C and it’s holding pressure at 32 PSI so no recharge needed. I think next step is a professional diagnosis now that I’ve done what I’m comfortable with. It’s working about 75% of the time, so it’s fine for now. Will report back when the pros do diagnostics.

 

[a4edwin]

I’ve been reading a couple of threads where they replace the big fuse that’s mounted to the firewall close to the battery fixing problems with the voltage drop.

 

[RST Dana]

32psi is the low pressure side, not the high pressure side. You will need grownup tools and knowledge to adequately pressure test both sides.

 

[KATfishing]

Hi all - Just reporting back to this thread for the archive. The AC problem finally revealed itself in the fullest as I was pulling our camper on a 4-hour trip in WI. The clutch locked up solid and the AC belt began its loud, smelly decomposition. Nothing like being on the road pulling a load to completely lose AC in 90+ humid weather, also to wonder if something more was going on with the noise and burn smell. After pulling over and lifting the hood for a visual inspection, decided to continue on. Thankfully, it was contained to AC system. This time, we let the trusted GMC dealer replace the compressor/clutch, tensioner and belt. It's blowing cold and running great now. Speaking of blowing, it was $145 diagnostic + $1,500 parts and labor -- all OEM, but it's fixed. I also had them fulfill a recall claim on the airbag replacement. Related/unrelated, my airbag light had come on a few weeks ago, and it coded as the Left Front Impact Sensor, of which they quoted $530. While I paid another $145 diagnostic fee that was part of the quote (didn't have a scanner that reader SRS) to learn that, I made myself feel better by buying the sensor for $70 from Autozone and installed it myself. Light off! Regarding the AC clutch, I'm thinking it must have begun failing when symptoms first came about. As always, I appreciate all your thoughts and perspectives when trouble shooting. THANK YOU!