98 Neon AC question

Tiny
KEGELMTA
  • MEMBER
  • 1998 DODGE NEON
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 150,000 MILES
I am working on an AC problem on a 1998 Neon with 4 cylinder engine. System has plenty of 134 in it but the clutch is not engaging or making a clicking noise when the AC is turned on by my assistant and key is in the on position but the engine isn't running. There are two wire harnesses that attach to the compressor. Each of the harnesses has 2 wires in it. One of them does have 12 volts and the other does not. I have checked the AC relay and the fuse and both are good. Any suggestions on what might be causing the AC compressor clutch not to engage? I can also turn the clutch by hand so the compressor is not locked up. I believe the person who charged the system did not evacuate it so I'm sure having air in the system prior to charging it is not particularly good for the AC system as a whole.
Friday, August 5th, 2011 AT 1:01 PM

7 Replies

Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
You need to be testing this with the engine running. The computer knows the difference. You will have to follow a wiring diagram of the circuit to locate the source of the problem. You may even need a scan tool.
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Friday, August 5th, 2011 AT 1:39 PM
Tiny
KEGELMTA
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Testing for voltage in that ridiculously small space while the engine is running will be dangerous. At least I only need to test one of the 2 wire harnesses. I'll see what the scanner says first. If the same 2 wires do not supply 12 volts while the car is running, I'll probably rig up a 12 volt supply to the harness that is not supplying 12 volts and see if the clutch engages. If the clutch engages, the high pressure shutoff could be preventing the clutch from engaging.
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Friday, August 5th, 2011 AT 2:01 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
There are many, many reasons for the compressor to be shut down and the circuit has to be troubleshooted by someone that understands how it works.
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Friday, August 5th, 2011 AT 2:06 PM
Tiny
KEGELMTA
  • MEMBER
  • 19 POSTS
I understand how airconditioning in automobiles works. I've charged and repaired 100s of AC systems for over 25 years. BTW, you provided me with no help earlier this week with the Toyota '02 engine swap to '05 toyota engine which I figured out on my own (your suggestion was air pockets). As I thought, I had to switch the heater hose back to the 02 hose & once I did that, its been running like new. It would be more helpful if you would list the more commonly encountered causes for why something isn't working rather than state that the system "has to be troubleshooted by some who understands how it works". Please don't bother replying; I'll figure it out for myself (again).
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Friday, August 5th, 2011 AT 2:29 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
No problem. If you think you're up for the task, here is what you need to find the problem.
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Friday, August 5th, 2011 AT 2:38 PM
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
Don't say I didn't warn you if you poke that testlight in the wrong place and fry the PCM
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Friday, August 5th, 2011 AT 2:46 PM
Tiny
KEGELMTA
  • MEMBER
  • 19 POSTS
Now thats what I'm talking about! Thank you!
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Friday, August 5th, 2011 AT 2:47 PM

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