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AC compressor won't engage after timing belt change

 
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Old 23 Jul 2018, 08:20 am
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Default AC compressor won't engage after timing belt change

hi everybody, this may be covered somewhere else, but I couldn't find it anywhere. I just changed the head gasket, timing belt, water pump, etc on my 2008 PT 2.4 non-turbo and now my AC compressor will not engage. I think maybe I damaged the connector(s) while jacking the engine up/down. however. I don't see any damage to the connector or wiring, but I can't find what I must look for when testing the wires with a DMM to see if the compressor is getting everything it needs to run. can anyone help me with diagnosis techniques? THANKS!!!
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Old 23 Jul 2018, 08:24 am
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Default Re: AC compressor won't engage after timing belt change

I damaged a ground when doing my timing belt, The AC didn't work at that point, but after it was fixed, the mechanic that did it fixed two bad grounds, I think one in the compressor area the other on the low pressure cutoff switch.

I'd check for bad grounds
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Old 23 Jul 2018, 09:27 am
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Default Re: AC compressor won't engage after timing belt change

thanks for that info!! I checked the two wires going to the compressor (power connector?) with the key in 'run' and with the AC switch on or off of it reads 10.7V. the ground wire (black) shows a solid ground to the battery terminal but the "hot" DB/B wire shows 10.7 regardless of whether the switch is on or not
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Old 23 Jul 2018, 11:09 am
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Default Re: AC compressor won't engage after timing belt change

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Originally Posted by jeff180 View Post
thanks for that info!! I checked the two wires going to the compressor (power connector?) with the key in 'run' and with the AC switch on or off of it reads 10.7V. the ground wire (black) shows a solid ground to the battery terminal but the "hot" DB/B wire shows 10.7 regardless of whether the switch is on or not
Is your compressor clutch not engaging while driving around? Apply 12V from an external power source and listen for the clutch to click on and off.

Check your battery voltage. It should read 14V with the engine on and at least 12V with the engine off. You did put the alternator belt back on and adjust the tension right?

Just checking the obvious.
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Old 23 Jul 2018, 12:27 pm
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Default Re: AC compressor won't engage after timing belt change

i'm sure the alternator is working properly, but I believe the AC compressor clutch is not engaging. I just got the car running again yesterday. we took it out and the AC wouldn't get cold. when we got home, I opened the hood and had my wife turn the AC on (no "click or engine bog). I also turned the HVAC controls to 'defrost'...nothing again. the car starts and runs great. so, this morning I pulled the connector on top of the compressor, turned the key to "run", turned on the AC, put my DMM on the connector....10.7V....i went from the black wire to the chassis.... .02ohms....from the black wire to the battery......12.56V. from the power wire to the ground wire (in the connector)….10.7V. from the hot wire in the connector to the chassis......10.7V. I conclude the power wire in the connector is only seeing 10.7V regardless of the HVAC switch position with the engine not running and the ignition in "run'. I have no idea what this means. PS: I also replaced the cooling fan.

Last edited by jeff180; 23 Jul 2018 at 12:31 pm. Reason: adding text
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Old 23 Jul 2018, 03:48 pm
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Default Re: AC compressor won't engage after timing belt change

ok, I figured out a way to keep the DMM connected while I started the car....it DID go up to 12.1V when running. so, now i'm really stumped. I didn't discharge the AC system. I worked around the lines. I THINK if I had cracked a line, I would've heard it. i wasn't rough with them. any ideas? thanks!!!
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Old 23 Jul 2018, 04:17 pm
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Default Re: AC compressor won't engage after timing belt change

I would suggest checking the Freon level. Anytime you move the engine there is a potential for A/C hoses to start leaking.
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Old 23 Jul 2018, 04:54 pm
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Default Re: AC compressor won't engage after timing belt change

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Originally Posted by jeff180 View Post
ok, I figured out a way to keep the DMM connected while I started the car....it DID go up to 12.1V when running. so, now i'm really stumped. I didn't discharge the AC system. I worked around the lines. I THINK if I had cracked a line, I would've heard it. i wasn't rough with them. any ideas? thanks!!!
It's completely doable to safely replace the timing belt and head gasket without disconnecting the A/C lines. I did that last week.

I don't want you to be chasing red herrings but your car voltage seems low

My UltraGauge reads fairly steady at 14.00V when the car is running. What is the battery voltage with the engine off and what is the voltage with the engine running?

When running, the voltage on your car should be 13.5V - 14.5V

The High Pressure cut out switch is one of those connectors that can be damaged when raising the engine to get to the bracket bolts.

Check the condition of the high pressure cut out switch. It's location is shown in this message:

07 PT Cruiser AC switch

With the clutch coil connector off, what is the resistance between the A/C clutch coil terminals? It should be between 2 and 5 Ohms.

It's best to test the clutch off the car but if you can safely power the clutch terminals with 12V you should hear the clank of the clutch engaging. You'll need a power supply that can put out 12V and 6 Amps. Just make sure everything else is disconnected from the clutch coil lines so you aren't feeding the external power supply back into the car's electrical system.
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Old 23 Jul 2018, 05:55 pm
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Default Re: AC compressor won't engage after timing belt change

Try jumping the AC low pressure switch and see if the compressor kicks in. If it does and it blows cold the switch is most likely bad. If it engages and does not get cold you probably have a leak.

When I was replacing my 02 sensors I managed to kill my low pressure switch. I think I might have pushed on it. Things happen.
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Old 24 Jul 2018, 02:20 am
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Default Re: AC compressor won't engage after timing belt change

the unusual voltage drop indicates a series voltage drop caused from a high resistance and there's not enough current to engage the AC compressor. this means opening the wiring harness and carefully inspecting for damage on the specific wire. it could also be at the junction point of the relay or fuse box.

you can also try measuring the voltage and manually manipulating the wiring harness until the voltage goes to 0 or BV (battery voltage)

i have also seen bad ground wires and ground points also cause a low voltage from a signal or control circuit.

either way you need to get the proper wiring diagrams to do this job
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