1986 Bronco II A/C clutch field coil - no power

[RonD]

Diag1
(it does have an accurate diagram of WOT relay, 5 pin, passes 12v when OFF)
331 and 361 activate the WOT relay, which is never activated, lol
(Diag2)
Looks like these 2 red wires run to 4 pin connector along with the "monitor" wire, B/Y wire, that lets the EEC known AC is on, not a control just a monitor so EEC knows if it should activate the WOT Relay, connector would not be unused if no Factory AC

Diag1
348 is 12volt IN from AC on switch
347 is 12v OUT to AC clutch

Diag3
WOT relay/ECC wire connector, probably not connected if no Factory AC
This connector could be unplugged and AC would still work fine just no WOT relay control

Don't see the pressure switch but it will for sure be there

AC switch------pressure switch------WOT relay--------AC Clutch---ground

 

[jbldsdad]

RonD - THAT was the gem I needed!

"WOT relay/ECC wire connector, probably not connected if no Factory AC. This connector could be unplugged and AC would still work fine just no WOT relay control."

I was not getting 12v to the B/Y wire at the WOT, even with the a/c switch on. I was starting to wonder if the WOT was bad, as I do get 12v at 361 (R). I decided to try disconnecting EOBB-14A459-A (Diag3).

Then I was getting 12v at 347 (B), and on the near side of the pressure switch. (Nothing on the other side, but I presume that's because the pressure switch is disconnected...'not enough pressure'.) So I removed the pressure switch and jumped the 347 circuit. (Of course, 12v on the far side of the pressure switch connector) and 12v at the a/c clutch relay!

Leaving the pressure switch connector jumped, I reconnected the a/c clutch connector and (KOEO) pressed the a/c switch in the cab. "click". . Then (KOER) I had my wife press the a/c switch in the cab as I watched the clutch engage and the compressor's working. (Hoses are all disconnected, so I didn't want the compressor to sieze. No idea how much oil is in there.)

NOW...why?

I've spent a lot of time (and a bit of cash) trying to get this B2 back functioning and looking decent (despite it's age) without shortcutting. My OCD just twitches at the idea of that connector remaining disconnected when they obviously fit. I have no idea of that a/c is after market or not. (It looks as old as the everything else under the hood) As you mentioned, disconnecting 14A459 will disable the WOT from 'pausing' the compressor when under load. Fine, it'll drive up hills a little slower; but I have to ask "why?". Or maybe what else would it take to regain WOT behavior?

If I'm tracking...those red wires (361 & 331) end up at the computer. (Short unwrapping18 inches of electrical tape to the firewall - the diagram suggests that's the case). B/Y wire (347) ought to end up at the computer as well. That B wire going to ground (coming out of the blue connector) looks like a 'shortcut', and the purple wire heading down the EEC wiring harness - I have no idea where it ends. (No such coloring in the manual) However, if B/Y should be connecting at 'pin 10' on the EEC...I could simply run another - back to factory specs.

Check my logic, but I'm guessing the purple wire is shorting the circuit (wherever it goes) and was mis-wired, causing this problem in the first place.

 

[RonD]

Most car makers disable AC clutch for start up, i.e. no compressor engagement when cranking the engine over
Most did it with ignition switch, the AC "demand" wire on climate control doesn't have 12v when key is turned to START, same as radio or other un-needed electrics lose power with key in START, so starter motor gets all the batteries power

Ford may have used the WOT relay for this since the computer needs to stay on for start up.
Computer already has software to not turn on the fuel pump relay until RPMs are above 400
So it would be easy to turn on the WOT relay, cutting power to AC Clutch until RPMs were above 400
Cranking speed is 200rpms
Don't know that they do this, I would think the ignition switch in START would be easier, but no telling what engineers think is "the best way" to do something