Testing AC compressor

Reply Subscribe

Thread Tools

Search this Thread

Sep 17, 2010 | 06:15 PM

TheKirbyMan

Thread Starter

Posting Guru

Joined: Aug 2009

Posts: 2,271

Likes: 2

From: Mexia, TX

Testing AC compressor

1981 F-150, factory AC. System is currently incomplete, the compressor is not in the vehicle.

I just picked up a wiring harness for AC for my truck. My previous harness was missing the connectors for the AC compressor and fast idle solenoid (the part that raises the idle speed when the AC is on), and now I have all the necessary connectors.

I'm wanting to test an AC compressor I have to see if it's any good; but due to the system not being together and functional yet, I can't get power to the compressor due to the pressure switch on the accumulator.

I've heard that you can jumper the two contacts in the accumulator's connector on the harness and that will allow the compressor to get power. Is this correct?

Or is there another way to test the compressor to see that the clutch engages?

Sep 17, 2010 | 07:01 PM

Archion

Logistics Pro

Joined: Jan 2007

Posts: 3,827

Likes: 103

From: Martinsburg, WV

That or you can apply power to the clutch directly. Just dont doi it with the engine running if you are unsure of the oil level.

Sep 17, 2010 | 07:59 PM

kermmydog

Post Fiend

Joined: Oct 2003

Posts: 9,176

Likes: 4

From: Western Central NV

You can't tell if the compressor is good until it is hooked up & operating. The compressor can come on the clutch can work & the compressor can still be bad. These compressors are known to have bad compressor plates. Which means they will not pump as they should. I personally would never used a used compressor for these Fords. I have put in two re maned compressors in my 86 F250 4x4 in the 13 years I have owned it. The first one went 12 years, I just installed the second one along with a new orifice, drier, & had to flush the system because when the compressor went out it sent metal throughout the system. YET THE COMPRESSOR STILL CAME ON, JUST WOULDN'T COOL.
Craig

Sep 17, 2010 | 08:57 PM

TheKirbyMan

Thread Starter

Posting Guru

Joined: Aug 2009

Posts: 2,271

Likes: 2

From: Mexia, TX

That makes sense, I didn't think of that. Are remanned compressors very expensive? My system has been open for as long as I've had the truck, so I'm going to have to replace a bunch of components anyhow.

Thanks for the replies

Sep 17, 2010 | 09:39 PM

redlightning93

Senior User

Joined: Jan 2006

Posts: 566

Likes: 2

From: Mobile, Alabama

Here is a good test procedure:

Automotive AC Information Forum - ACKITS.COM

Sep 18, 2010 | 03:02 PM

TheKirbyMan

Thread Starter

Posting Guru

Joined: Aug 2009

Posts: 2,271

Likes: 2

From: Mexia, TX

Thanks for the link!

Well, just out of curiosity I jumpered the pressure switch contacts with a short wire and checked to see if the clutch would at least engage....nothing. Either something's unhooked or not functioning somewhere along the line, or the compressor is bad. On the new harness I picked up, it does have an extra grey connector that the old harness didn't have; everything else hooks up like the old harness. I wonder if this has anything to do with why the clutch didn't engage?

Sep 18, 2010 | 03:28 PM

bashby

Post Fiend

Joined: Nov 2005

Posts: 7,437

Likes: 4

From: Charles Town, W bygod Va

You should have power to one of the terminals on the low pressure switch, It probably gets power from the ac switch on the climate controls, which gets power from a fuse. I'd try to get a wiring diagram to confirm, or you could confirm power and ground at the ac clutch while jumping the low pressure switch. If you have both then the clutch is bad. You should also check to make sure the center hub of the compressor will turn by hand.