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2003 chevy trailblazer_lt
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Discussion Starter · #1 ·
I recently purchased an 2003 trailblazer with ac problems. I have a 02 that was overturned that I am using for some parts. This is an excellent site for information and it has helped me twice, but I still have one problem I can't seem to find the answer for.

The ac clutch works sporadically. I have jumped the low switch on the dryer and the clutch attempts to engage and sometimes it does. Once the clutch does engage it works well, yet if I turn off the motor and restart....it will not start again.

Compressor, wiring, .....???? any suggestions would be helpful.
 

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2004 gmc
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Possibly low voltage going to the clutch by way of the fuse and relay. If corroded or loose sockets cause high resistance connections, the voltage may be intermittent or low at the clutch. Or the wiring could have a loose connection with the same result. Or the clutch could have weak magnets, internal coil intra-winding shorts causing weak pull-in force, and so forth. Then you'd need to swap the clutch assy or the entire compressor.

Are you certain the refrigerant charge and pressures are proper?
 

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2003 chevy trailblazer_ls
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Yep, :iagree:

Are you sure you have a good connection when you jump the low pressure switch? A big paper clip works well.
Dave
 

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Discussion Starter · #4 ·
I checked the level and it was within range. I believe I need to double check that.
I will do some wiring checks also. :)
 

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2003 chevy trailblazer_lt
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Discussion Starter · #5 ·
Yep, :iagree:

Are you sure you have a good connection when you jump the low pressure switch? A big paper clip works well.
Dave
we used a heavy wire for the jumper. You can see the clutch tighten...then release when I remove the jumper wire. ...sometimes it engages fully
 

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2003 chevy trailblazer_lt
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Discussion Starter · #6 · (Edited)
compressor/clutch problem

I tried a heavier jumper wire on the low side and the clutch will engage every time. After about 5/10 minutes of the motor running the clutch disengages and will not come back on no matter what I try.

Is this an overheating clutch? and can I just replace this or most likely the entire compressor?

Thanks for any suggestions!!!!

btw low pressure reading is 40-45 at 90 degrees.
 

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One way to eliminate that would be to apply 12V directly to the clutch and see how it reacts. You would have to rig two wires from the clutch. Connect the - to a good ground and keep the + in your hand. Touch the wire to the + of the battery and see how it operates without starting the engine. If it seems to be working OK, start the engine and turn on your A/C to max. Engage the clutch with your wire and see how it works. Let it run a while and see how it goes. Cycle it a few times on and off to mimic the low pressure switch. If it has trouble re-engaging, it could be a couple of things:
- failing magnetic clutch. As it gets hot, it loses its ability to create a magnetic field
- Refrigerant pressure too high. High side of system too high, preventing compressor from starting again when hot. This can only be verified with a set of gauges.

If it runs fine in all situations, I would suspect either bad wiring or relay or a dirty plug. BTW, your low side pressure seems a bit high to me. At idle, the switch should cycle off at about 25psi, which supports the possible high pressure scenario. Either the system is blocked or overcharged. As far as replacing just the clutch, I don't think it's worth the trouble as the rest of the compressor is probably not too far behind.
 
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