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2002 chevy trailblazer_ltz
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11 Posts
Discussion Starter #1
I searched the forum, didn't see my issue so thought I'd give it a shot. AC compressor wouldn't run for more than 10 minutes before turning off completely until the engine cools and the 10 minute cycle would reset. Additionally, I had to replace the fan clutch (needed, it locked up [and the ac didn't stop blowing cold but more on that later]) and water pump (I was already in there so why not). Also added refrigerant and changed the switch on the evaporator.

The AC still doesn't cool as it should. Warmer days or while driving 40 average it runs cold a little longer but goes back to blowing hot air after 15 or so minutes. Cooler days or driving 55 avg the ac blows nice and cold. As of last week school traffic began and, in very slow traffic, the coolant temp spiked from 210 normal to 240 and the fan did not engage (it would have sounded like a jet). Fan fuse blown (replaced). Happened again. Fan fuse good. Swapped working low beam relay with fan relay with no change (and lows work). Double checked physical connection at fan shroud (good). Come to think of it, I have never heard the fan clutch engage since replacing it... not even when the ac is on.

What did I miss? Why won't the fan clutch engage? This all has to be related.
Thanks.
 

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2005 gmc trailblazer_ls
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160 Posts
Very carefully inspect harness and connector which is plugged to fan clutch connector for corroded or disconnected wire. Mine had broken off two wires and created weird problems with the cooling and A/C. Hope this helps

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2006 chevy trailblazer_lt_ext
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286 Posts
I do know that these vehicles will shut down then AC as part of a cool-down strategy if it thinks the engine is overheating.


First order of business: what are the high and low side pressures on the AC system, both before a cold start, and after running for 5 minutes.
 

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2002 chevy trailblazer_ltz
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11 Posts
Discussion Starter #4
I do know that these vehicles will shut down then AC as part of a cool-down strategy if it thinks the engine is overheating.


First order of business: what are the high and low side pressures on the AC system, both before a cold start, and after running for 5 minutes.
I don't have access to a pressure gauge today but I'll update as soon as I do. Thanks.
 

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2002 chevy trailblazer_ltz
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11 Posts
Discussion Starter #5 (Edited)
Update: I haven't been able to really get under the hood due to a death in the family and crappy weather but I looked at the wiring harness and to me it looks fine. All of the wires seem to be connected. Edit: I really think it has something to do with the fan clutch as it only engages briefly at cold engine startup and doesn't when it gets hot.
 

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2005 gmc trailblazer_ls
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160 Posts
Things to consider. Is the fan clutch aftermarket? Also is the fan clutch electronic relay aftermarket? How about swapping headlamps electronic relay with the clutch relay temporarily.

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