I recently just put in a a/c compressor and drier in my 2001 honda civic lx (6/18/2014). Now, when i go to turn the a/c on (with the car running) the clutch does not engage. Why? And how do i fix that?My father in-law said it could be that it's not getting any power to it. How do i trace something like this if possible? Any all feedback would be greatly appreciated

 

And you evacuated the refrigerant lines with a mechanical vacuum pump and then charged the proper amount of refrigerant by weight?

There is a switch to cut off the compressor when there is no refrigerant pressure, because running it dry will cause damage.

 

Yeah i evacuated the system for over an hour. And we're using gauges for the refrigerant. My father in-law put some refrigerant back into the system but i knew it wasn't enough i just didn't say anything. I think he put 1 1/2 cans in it before he asked me to try and see if it would work and it didn't and that's where we stopped and assumed it was an electrical issue. How much refrigerant should be in it for the compressor clutch to start engaging?

 

You need about 50 psi to close the switch. The switch is on the high side, so once the compressor starts, the pressure there will only go up. If the pressure goes over 450 psi, the switch will open again-- it has a dual function to protect against over- or under-pressure. The switch should stay closed all the time in normal operation.

So putting in more than a whole can will be enough. Rated amount is about 18 oz IIRC (check sticker under the hood), so don't use more than 1.5 12 ounce cans.

Do the condenser fans come on when you press the A/C button with the engine running? If not, unplug the switch and check that it is a closed circuit. If they do, the compressor should be starting. Check that the compressor gets power when it should start. You can jump the compressor to the battery to see if the clutch pulls in, but do this only with the engine OFF. Jumping the compressor with the engine running will cause an immediate over-pressure because the car doesn't know to start the condenser fans. And you don't have the protection of the switch either, so it is likely that the high side hose will blow.

What was wrong leading to replacing the compressor in the first place?

 

Yes both condensor fans come on. Ok, we tried jumping the compressor last night and it didn't work. Does the compressor need to be grounded? As far as the pressure switch goes, I didn't think to check/change that at all. I'll check that next and check the refrigerant amount too

 

Compressor doesn't engage when you jump it means the problem is at the compressor. Yes it needs to be grounded, it should of course be bolted to the engine which makes the ground. The resistance through the clutch circuit (from the compressor wire to ground) should be 3 or 4 ohms. If it is open circuit, find out where it is open, likely either the coil or the thermal switch.