NEED HELP Automatic climate control

corky

Registered Member
Original poster
Jan 23, 2012
44
Portland OR
So I can't find a lot of info on my problem, most of it doesn't apply. My a/c works find when the outside temp is in the 70s bit will work for only 10 to 20 minutes when it's above 80, the out side temp reads correctly, the little fan need my ear appears to be functioning, my freon press reads right and there are not any leaks. Once it shuts off it won't go come back on for quite a few hours, I have ordered another control head but haven't received it yet, any ideas or people that have had the same problem find the fix. When it happens the compressor pulley is not engaged, the fuses are fine and the blend doors work properly.
 

MRRSM

Lifetime VIP Donor
Oct 22, 2015
5,917
Tampa Bay Area
If it is STILL located in the same spot on your 2003 Trailblazer 4.2L SUV as is depicted in this Video...Try changing out your Ambient Temperature Sensor after considering this Guy's experience with successfully reconciling a similar "Phantom Temperature Change" Behavior:


AMBIENTEMPSENSOR.jpg

 
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TJBaker57

Guru
Aug 16, 2015
2,074
Colorado
So I can't find a lot of info on my problem, most of it doesn't apply. My a/c works find when the outside temp is in the 70s bit will work for only 10 to 20 minutes when it's above 80,

my freon press reads right

... there are not any leaks. Once it shuts off it won't go come back on for quite a few hours,

When it happens the compressor pulley is not engaged,


What are your high and low pressures and at what ambient when read?

Do you have an OBD adapter? You can see the high pressure with one of those.

If you are at highway speeds does it still shut off after 20 minutes or so?
 

Matt

Guru
Dec 2, 2011
3,878
I'd say your clutch is going out. I had the same sort of issue, changed the control head as well (but it had issues) and it still did the same thing. About 6 weeks ago I changed out the compressor and it's been mint ever since.
 
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corky

Registered Member
Original poster
Jan 23, 2012
44
Portland OR
What are your high and low pressures and at what ambient when read?

Do you have an OBD adapter? You can see the high pressure with one of those.

If you are at highway speeds does it still shut off after 20 minutes or so?
All my driving is at highway conditions, going to work in the afternoons when it runs for about 15 minutes coming home at midnight it runs untill I get home which is about 45 minutes, they put the gauges on it at work and said the high and low were fine, just frustrating that it works great when it's cooler out side than when it's hot, and the outside temp gauge appears to be reading correctly
 

corky

Registered Member
Original poster
Jan 23, 2012
44
Portland OR
Prior to changing out your compressor, consider removing the air-gap shim. I had dissimilar symptoms but removing the air-gap shim has kept my air cool for over 8 years.
Not familiar with an air gap shim, is it behind the clutch
 

TJBaker57

Guru
Aug 16, 2015
2,074
Colorado
All my driving is at highway conditions, going to work in the afternoons when it runs for about 15 minutes coming home at midnight it runs untill I get home which is about 45 minutes, they put the gauges on it at work and said the high and low were fine, just frustrating that it works great when it's cooler out side than when it's hot, and the outside temp gauge appears to be reading correctly

Well that lessens the likelihood of it being an airflow through the condenser problem or a high pressure cutout problem and maybe even the airgap issue as from my own experience all of the above seem to occur more often at high ambient temps and lower speeds when the high side pressure shoots up and the system is generally under more stress.

I will have to say that without actual numerical values, "just fine" doesn't carry much weight as a diagnostic tool. Admittedly, I am not so experienced in the automotive A/C arena, however I have been in the residential and commercial A/C field since 1984, and I see an alarming number of technicians who don't really know how it all works! I am a big fan of gathering hard data to see just what is happening at realtime rolling down the road.
 
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budwich

Guru
Jun 16, 2013
1,737
kanata
you need to get access to the controller and with a meter find out what's up... but at this point, the one test that you can do is meter the connection at the compressor clutch. do this when you know it is working and again when it stop... basically disconnect the plug, measure the resistance towards the clutch and do the same towards the controller... compare the results at the two different "events".

one question: when was the AC last serviced?
 
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Mooseman

Master Blaster
Moderator
Dec 4, 2011
22,325
Ottawa, ON

TequilaWarrior

Active Member
Dec 5, 2011
454
Central Pennsylvania
Not familiar with an air gap shim, is it behind the clutch
"Yes" - see @Mooseman 's post above.
Bonus: it's free! (Excluding your time.) While I had mine apart, I cleaned up the clutch mating surfaces a little with a wire brush on a dremel-like tool. While I stated my symptoms were dissimilar, they weren't completely different either. The hotter it was, the less likely it was for my clutch to engage properly. The dead giveaway for mine was a brief, high-pitched "chirp", that was the sound of the clutch attempting to engage for a moment and the magnetic force not being strong enough to hold it engaged. This sound occurred I believe on a 9-second (ish) cycle. Regardless, it only costs "time" to try and could prevent a high-dollar repair that would be a lot more lengthy.
 
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