How to know if A/C compressor gets power.

[motorsports_3]

I took out my a/c compressor but i do not think it was bad. It turns out it was disconected and had a bad fuse. It still may be bad, but i want to make sure before buying another one. I pput the fuse in and put a test light to the ONE wire that goes to the compressor. I grounded the test light but no light came on. How do i test if it has power?

[dark89e30]

Get rid of the test light and use a voltmeter. Also, you want to measure the resistance of the compressor clutch coil circuit. Do this by putting one probe of your dmm on the connector wire (compressor side), and since there is only ONE wire to power the clutch, I assume that the compressor is self grounding so put the other probe on the casing. You want to compare the # of ohms with the factory spec or that of a known good unit. If there is infinite resistance (open circuit) the compressor is bad. If the resistance is too low, then there is probably an internal short which would cause a fuse to blow as well as not work properly.

[AndrewBird]

If you aren't getting power to the compressor, then your test isn't going to work. Figure out why there isn't power going to it and THEN test if the compressor is bad.

I would start by looking for a short somewhere in the wiring, grounding out the wire. Might be the reason the fuse was blown.

[jlevie]

Power won't be applied to the compressor clutch if either limit switch in the dryer is active. Since you've had the compressor out there's no charge in the system and the low-limit switch will prevent power from reaching the clutch. For a quick test to see if the compressor will run you can jump power to the clutch. That'll tell you if the clutch works and whether the compressor is making loud noises, but you'll have to charge the system and check pressures to tell if the compressor is good.

[motorsports_3]

...

Power won't be applied to the compressor clutch if either limit switch in the dryer is active. Since you've had the compressor out there's no charge in the system and the low-limit switch will prevent power from reaching the clutch. For a quick test to see if the compressor will run you can jump power to the clutch. That'll tell you if the clutch works and whether the compressor is making loud noises, but you'll have to charge the system and check pressures to tell if the compressor is good.

Ahh it all makes sense now. I went ahead and ordered a compressor anyway so we will see what happens

[xLibelle]

oh my f'n god, three points of attack within 3 replies to the OP... its the most productive thread evaaaaarrrrr!!