You might remember me from before, maybe not. I have a 2000 F-150, 5.4 triton. New a/c compressor (properly filled and cycled) installed. New accumulator (oil added), orifice tube replaced. System evacuated for an hour and a half, and held vacuum well over 5 min. System took the first can no problem, and half of the second. Compressor never kicked in, just like before. Measured air gap for .030, and couldn't get it in. Jumpered the low side switch and nothing. Plugged everything in and measured for 12v and gound at the compressor, it had it. Disconnected the connector, and checked for continuity through it, it was good. I'm stumped, you got any ideas? Its a brand new motorcraft, not a reman. Ordered from rockauto. Also I swapped the clutch relay with a known good, as well as the diode, but that doesnt really matter if the damn thing is getting B+ and ground! Help!!!!! It freakin 102 degrees here!!!!!

 

Grab your multimeter and put it on the lowest OHMS setting.

Pop open the under hood fuse box and identify the AC clutch diode. Observe its orientation so it goes back in the correct way later, then remove it. Also, remove the WOT (AC CLUTCH) relay.

Connect the negative meter lead to the negative battery post.

Measure resistance from each terminal in the diode's socket to ground:
A) The anode connector should measure 0 ohms.
B) The cathode (band) terminal should measure through the coil to chassis ground and should be around 3-5 ohms.

If both are correct, go to socket pin 5 in the WOT relay socket and repeat measurement, results should be the same as B above.

If everything checks so far, reinstall the diode.

Switch the meter over to DC Volts and check for battery voltage on relay socket pin 3 which is an ALWAYS HOT circuit provided by Fuse F13 in the same fuse box.

If that checks good, connect a fused (15A) jumper between pins 3 and 5 of the relay socket and see if the clutch clicks or pulls in.

Lets see how far you get on that sequence and what the observations are.

 

Everything is off. Battery connected. A/C diode 502 anode socket to ground reads 10.5 ohms. Cathode socket to ground reads open. A/C Clutch relay 204 pin 3 reads 12v. I couldnt find the wide open throttle relay, but the symptoms didnt call to move forward anyway.

 

I think I replaced the compressor for no reason...

 

Yeah, maybe so.

WOT Relay= AC Clutch Relay, FYI.

1. Did you verify meter zeros (reads 0 ohms when the probe tips are shorted to each other)? Don't want to make any diagnosis without confidence in the test gear.

2. Perform continuity checks (zero ohms) as follows: Several may fail and should show the wiring section(s) that is(are) faulty. List each result.
A. Battery negative post to ground G102 (located on fender apron, pass side, below the hood strut lower mount)
B. AC Relay pin 5 to the cathode of the diode.
C. AC Relay pin 5 to the "switched HOT" wire (Gray/White) on the compressor clutch connector.
D. Ground wire (Black) on the compressor clutch connector to G102.

3. Verify the clutch coil reads 3-5 ohms.

Those readings should pin down the circuit segment(s) with the problem.

 

Alright, I got it figured out. Man, sometimes you get em quick, sometimes it takes a day or so! The contacts inside the connector were backed off just enough to not make contact, but just forward enough to read with the meter. Seems like a straightforward fix and you'd think it would've been easy to find, but man, I thought about it all day at work until it came to me as a possibility. Thanks projectSHO89 for the help yet again. She's full of 134 and blowing around 55 degrees on a 100 degree day.

 

Good deal.

I actually thought about adding a step for a visual exam of the pins of the connector Sunday evening, but I got distracted and didn't include that in my instructions.

Glad you got it finally.

 

Lol, yeah...some times you just don't think about it all the way through when it's right in front of you. Grandpa would always make us take a break, smoke a cigarette, drink a glass of iced tea, and talk and think. I failed to do just that, until the next day at work!
Anyway...the "feel like" temperature today was 106. My vents were blowing a nice 43 degrees.