A/C Clutch and Coil Problem

[Mark Stephen Lammers]

I replaced the compressor and clutch with a used assembly on my 2001 PT Cruiser. I bench tested the coil with a OHM meter and was around 5 Ohms. 2-5 is a good coil. Hooked up 12 volts to the clutch and coil and the clutch pulled in just fine. Put compressor /clutch assembly back in car and clutch would not engage with the ac switch. Checked OHMs on the coil and it was close to .4 OHMs. Bad Coils. Applied 12 volts straight to the clutch coil and still nothing happened other than wires getting hot because of a short. Could it be a fluke that the clutch coil went bad or is something in the wiring caused it.? All my wiring checks out fine with the wiring diagram. Checked for continuity and power to connectors and nothing is bad.

I do have a question that is puzzling to me. In the line from AC relay to the Clutch coil, there is a diode. Symbol shows a Transient Voltage Suppression diode. I know what a regular diode is for but I have no idea what this diode does. Could this be a problem why it went bad? I’d hate to get another clutch and it burn up also.

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• 01-PT-ACWiring.jpg

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[Mark Stephen Lammers]

Thank you for all your help. I printed the wiring diagrams, pulled the connectors out of the PCM, and checked continuity from pin to pin and relay to pin.

Turned out to be a bad AC High Pressure Switch connector at the compressor. Wouldn’t you know, it was the last line I checked, instead of the first. I replaced the connector with a new one. AC clutch kicked on and High and Low speeds work on the radiator fan. AC is nice and cold.

[EricTheCarGuy]

Glad you got it sorted. Sounds like a long strange trip indeed. This is one of the reasons I don’t recommend AC work for the DIY. Without the help of cap269’s posts, I don’t think you would have made it this far. AC work involves a LOT of different systems and if you’re not familiar with how they work, you often end up wasting your time and money throwing parts at the problem. For future reference with HVAC issues.

http://www.ericthecarguy.com/faq/solving-automotive-hvac-problems

Thanks for the updates and for using our little forum.

[Andrew Phillips]

I’m glad I could help, but I’m even more glad that you got it fixed. AND, without having to buy expensive parts! :woohoo:

[Mark Stephen Lammers]

Hey Eric,

Cap269 did really help me out a lot. Just so everyone can learn from this post, I was a little weak in reading vehicle DC wiring diagrams. Maybe that is why I am a mechanical engineer and not an electrical engineer. Realfixesrealfast on Youtube, has several training videos on reading wiring diagrams. This guy is an amazing teacher. He illustrates and makes sure you know the material. I know the mechanics of a AC system, but in my opinion, knowing wiring diagrams is the “life blood” to trouble shooting it. Took me a few days, but now I am really good at wiring diagrams. Anyone can learn this. Just takes some people a little longer to understand. I’m very grateful for cap269 explained somethings in my learning process so I would fully understand.

Hope this post will help others in there quest to get it done right at a very inexpensive price.

Thanks again! Happy 4th of July!

[Author]

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