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2004 gmc envoy_slt
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Discussion Starter #1
I've read most of the threads about the fan clutch but none have what I'm looking for.

If I let the my 2004 Envoy (I-6) idle too long after starting it the condenser overheats and blows off freon. You can hear it when it does this, kinda sounds like when air breaks bleed. The system is then low on freon and the driver side air is warmer than the passenger side. I have re-charged the system a couple times only to have it blow out again.

I think the problem is the radiator fan is not fully engaging when i start the car. I am able to stop the fan with my hand and there is virtually no air flow from the fan. After the motor heats up the fan starts to engage and blows good. Is the fan clutch bad or is it some other problem? I want to make sure before I spend $200 on a fan clutch and the labor to replace it.
 

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2003 chevy trailblazer_lt_ext
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17 Posts
I had an intrepid that did this same thing. My high pressure switch was bad on my high pressure a/c line. It was a quick screw off / screw on deal. (had a Schroeder valve on the line)

The switch was reading the wrong line pressure and not making the fan kick on soon enough, allowing heat to build up and line pressure to get to high, which is why the bypass would blow off excess pressure.
 

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2004 gmc envoy_slt
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8 Posts
Discussion Starter #4
Yes. Very clear observation of fan clutch death.
The fan does engage correctly when the engine temp reaches 210 but not below 210. So the motor never overheats but the A/C condenser is. Is the fan supposed to be engaged at a cold start-up?
 

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2003 chevy trailblazer_lt_ext
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The fan does engage correctly when the engine temp reaches 210 but not below 210. So the motor never overheats but the A/C condenser is. Is the fan supposed to be engaged at a cold start-up?
do you have access to a gm diagnostic tool? if so, it will allow you to activate/deactivate certain sensors, and check the reading of other sensors. This would quickly tell you if the a/c line pressure is getting to high (from the condenser getting to hot) and causing the pressure relief valve to open. This would also give you the ability to lock up the fan clutch at any time to see if the line pressure sensor is reading incorrectly (reading temp/pressure lower than actual pressure)

the clutch fan is designed to not be engaged all the time, so that in theory you could grab the fan (if you were sure the clutch wasn't engaged) and stop it while the motor is running. if the fan clutch were to engage it would easily rip the fan from your grip though. a bad clutch would be one that either never engaged, or was locked up all the time.
 

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2004 gmc
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Sorry, I was a bit hasty last post. You didn't fill out your vehicle profile so I skipped over what you said it was in your post. (I'm used to just glancing inthe upper right corner for the vehicle details.)

In 2005, GM came up with new PCM programming to address an issue of insufficient AC cooling upon start-up, where the engine was cool and didn't need the fan to be running at high RPM, but the need for AC on a hot-after-being-parked vehicle was at a maximum.

THis was also when they were redesigning the EV fan clutch for its own reliability problems. Many members got both a new fan clutch and new PCM programming while in warranty in the 2005 time frame.

You might benefit from visiting the dealer for this updated PCM software, if you haven't had a reflash at the dealer for any other reason since 2004. It should force the fan to come on full at initial start up when cold.
 

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2004 gmc envoy_slt
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Discussion Starter #7
You might benefit from visiting the dealer for this updated PCM software, if you haven't had a reflash at the dealer for any other reason since 2004. It should force the fan to come on full at initial start up when cold.
I had the PCM replaced back in Nov 2008 so I would assume they updated the software then. I don't have access to a gm diagnostic tool. Is there somewhere I can go to borrow or rent one to check to see if it is a sensor?
 

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2002 chevy trailblazer_ls
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2,217 Posts
My 2002 had lousy AC the first 3+ years I had it, because of not enough air moving through the condenser coil. The clutch was redesigned in 2005 to have a higher minimum speed, and to respond faster to commands from the PCM. But it still takes a minute or more for the clutch to respond because the viscous coupling fluid takes time to move. The PCM update gave the PCM smaller increments of clutch engagement control. A new clutch will work fine with the old PCM program. A new clutch fixed my AC problem finally, after two dealers tried to fix the AC with reprogramming while it was in warranty. The new updated clutch didn't come out until I was 4 months out of warranty, so I got to buy it and installed it myself. Thanks, GM.

Also it sounds like the high pressure cutout switch on the compressor is not working if it's blowing off refigerant. (They don't use "Freon" anymore.) Supposed to cut out before it discharges.
 

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2006 gmc envoy_slt_xl
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Same problems on mine. I will be taking it back to the dealer soon to get the fan clutch replaced. I will let all know if this fixes my A/C problem. Thanks for the help.
 

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I've read most of the threads about the fan clutch but none have what I'm looking for.

If I let the my 2004 Envoy (I-6) idle too long after starting it the condenser overheats and blows off freon. You can hear it when it does this, kinda sounds like when air breaks bleed. The system is then low on freon and the driver side air is warmer than the passenger side. I have re-charged the system a couple times only to have it blow out again.

I think the problem is the radiator fan is not fully engaging when i start the car. I am able to stop the fan with my hand and there is virtually no air flow from the fan. After the motor heats up the fan starts to engage and blows good. Is the fan clutch bad or is it some other problem? I want to make sure before I spend $200 on a fan clutch and the labor to replace it.
I'm having this exact issue, did you find a solution?
 
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