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Discussion Starter #1
Have an issue with my 2006 LBZ.

After continued running with a/c on the evap core ices up and air flow drops considerably. It is not low on Freon but the compressor never shuts off. Even when jumping the low pressure switch. It only turns off via the dash selector.

Anyone run into this before?
 

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Jumping the low pressure switch will allow it to remain compressing. Unplugging the low side switch will stop the compressor.

Take out the blower module and get a look see. You say flow diminishes...icing over will be zero flow. Some creativity with a wand and you can blow through some of the core. I'd almost bet that the core is dirt covered and the condensation is sticking the the core.

If it looks really bad, you can always cut the duct work for the cabin filter mod, and really get a flexible wand in there.
 

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Discussion Starter #3
Jumping the low pressure switch will allow it to remain compressing. Unplugging the low side switch will stop the compressor.
Correct, unplugging the low pressure switch does not cause the compressor to disengage in this case.

Take out the blower module and get a look see. You say flow diminishes...icing over will be zero flow. Some creativity with a wand and you can blow through some of the core. I'd almost bet that the core is dirt covered and the condensation is sticking the the core.

If it looks really bad, you can always cut the duct work for the cabin filter mod, and really get a flexible wand in there.
Already cleaned the evap core.
 

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The low side switch is on the receiver drier unit, two wire.
Is that the one you unplugged?

Is it possible that the wire to the low side switch is shorted upstream of the connector?
 

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Discussion Starter #5
Black wire is <0.5 ohm to B- and green wire is 3.8k ohm to B-, key off.

Thought I recalled someone having this issue before and it was a PCM issue.
 

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Discussion Starter #6
It has been a while so here is a follow up.

After my Ohm results it was mentioned "there's the problem".
What it was is after doing the head gaskets and R&R the cab I swapped the low pressure plug with the coolant level sensor. Apparently it happens often on the GMT800. GM has always been good about not having components with same plug design so that never crossed my mind especially how close they are to each other.

So A/C is functioning fine now.
 

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It has been a while so here is a follow up.

After my Ohm results it was mentioned "there's the problem".
What it was is after doing the head gaskets and R&R the cab I swapped the low pressure plug with the coolant level sensor. Apparently it happens often on the GMT800. GM has always been good about not having components with same plug design so that never crossed my mind especially how close they are to each other.

So A/C is functioning fine now.
Glad your issue is resolved now.
Thanks for giving us an update!
(y)
 
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