A/c working backwards after 5.0 swap

[jake hunt]

I've searched and can't find enough info to fix this problem, 98 xlt explorer had 4.0 sohc, now has 97 5.0 with electric 4406 swap, I'm using the engine harness from the 97, but made a jumper to the 98 engine bay harness. (Been driving this around for a couple other years, just now getting around to hooking up the ac)
Any and all help is appreciated thanks!

 

[1998Exp]

It could probably help, if you explained what "A/C working backwards" actually means.

 

[jake hunt]

Haha right, I had it in my head that I typed it out, probably because I have been typing in the searches so many times, key on engine off "click" clutch engages in all knob settings, engine running clutch engages in every setting, (including off) except the a/c and defrost settings, switch to ac settings and clutch engages only at WOT.

 

[imp]

Haha right, I had it in my head that I typed it out, probably because I have been typing in the searches so many times, key on engine off "click" clutch engages in all knob settings, engine running clutch engages in every setting, (including off) except the a/c and defrost settings, switch to ac settings and clutch engages only at WOT.

@jake hunt
Wiring problem, I would guess. Driven a long time without A/C, "hooked it up", things don't work right. First off, the clutch is supposed to DISengage at WOT. You jumpered to the '98 engine harness. Do you have wiring diagrams for either year? I only have for '96, but could look into where you might have gone wrong. imp

 

[jake hunt]

I currently do not have diagrams for either year, It has been quite awhile since I did the swap and the jumper, I could probably used the c115 pinout to verify my jumper if anyone has them available

 

[imp]

I currently do not have diagrams for either year, It has been quite awhile since I did the swap and the jumper, I could probably used the c115 pinout to verify my jumper if anyone has them available

@jake hunt
I'll see what I can find. Won't go to shop till morning, though. imp

 

[jake hunt]

Thanks bud, I appreciate your help, the engine harness is early 97 btw.

 

[1998Exp]

It's backwards, indeed. I am going by the 98 EVTM book. It shows that the A/C clutch is controlled by a relay, which in turn, is controlled by the PCM. The relay has two connections: a red wire that goes through some junction to fuse #13 in the power distribution box, and a pink/yellow wire that goes to pin 69 in the PCM. The relay is activated when the PCM drives the latter wire to ground. Seems that you connected something wrong. One possibility is that the red wire goes to ground instead of +12 through that fuse. This will activate it when the PCM drives the control line high (to +12) - exactly the opposite from what you want.

 

[1998Exp]

Added note: I don't have any documentation for the 97, so no idea how things were wired there. It's almost certain that the PCM is a "low side driver", just like in the 98, because all vehicles of that era had their electronics controls done that way -- much simpler and cheaper than driving "high side". The other possibility is that the relay contacts are reversed. I would check the PCM control first. If the red wire (pin 2) is permanently at +12 and the pink/yellow wire on pin 1 goes from +12 to 0 when the A/C is supposed to kick in, you are fine there. Actually, the coil has no polarity, so these two wires can be reversed with no consequence at all. All that matters is that one end is constantly at battery voltage, and the other drops to ground when the compressor needs to kick in.
The output side of the relay should have +12 connected to pin 3 (pink/light blue wire). The A/C compressor (gray/white wire) should be connected to pin 5 of the relay (normally open). If it goes to pin 4 instead (normally closed), you found your problem.

 

[jake hunt]

I will trace those wires down, thanks, I never thought about it being my fault, haha everything has worked great so far, but it is very possible that I may have gotten mixed up with my jumper, that is the only place I messed with the wiring,

 

[jake hunt]

Verified my jumper, and it is accurately wired up. Early 97 must function differently than the 98, the 97 did have the message center but I wouldn't think that has any bearing on this since I am using the 98 body harness for the ac.......

 

[crispins]

Dude just use a relay to reverse the action.

It would take 5 mins to wire in and would fix the issue without any complicated time consuming diagnostics.

 

[jake hunt]

Feel free to walk me through that

 

[1998Exp]

Dude just use a relay to reverse the action.

It would take 5 mins to wire in and would fix the issue without any complicated time consuming diagnostics.

Not sure about the five minutes - probably more like an hour, assuming that the OE has a proper relay on hand, and knows how to do that logic reversal. Nevertheless, if the wiring error is not obvious, I would tend to agree with you. He will probably have to use a "normally closed" contact on the new relay, and feed it from some ignition-switched source, with an extra fuse. That's because the existing A/C fuse is "always hot", which, if used, will constantly energize the clutch when the vehicle is parked.

 

[crispins]

Not sure about the five minutes - probably more like an hour, assuming that the OE has a proper relay on hand, and knows how to do that logic reversal. Nevertheless, if the wiring error is not obvious, I would tend to agree with you. He will probably have to use a "normally closed" contact on the new relay, and feed it from some ignition-switched source, with an extra fuse. That's because the existing A/C fuse is "always hot", which, if used, will constantly energize the clutch when the vehicle is parked.

I would have to draw it up on some paper but it is not a hard circuit to make.

 

[crispins]

Feel free to walk me through that

Do you need me to walk you through it or have you found it out?

It is pretty easy.

PM me if you really want my help and I will make you an easy to follow diagram

 

[imp]

Guys, ..... "key on engine off "click" clutch engages in all knob settings, engine running clutch engages in every setting, (including off) except the a/c and defrost settings, switch to ac settings and clutch engages only at WOT."

If I am understanding this description correctly, more is involved than a simple WOT relay problem. Something is turning the clutch ON even with the switch in OFF position......Looking at the schematic for the Heater-AC Control Assembly, the switch isolates all the functions from ground when in the "OFF" position.
I'll study this a bit more tonight.......imp

 

[jake hunt]

Guys, ..... "key on engine off "click" clutch engages in all knob settings, engine running clutch engages in every setting, (including off) except the a/c and defrost settings, switch to ac settings and clutch engages only at WOT."

If I am understanding this description correctly, more is involved than a simple WOT relay problem. Something is turning the clutch ON even with the switch in OFF position......Looking at the schematic for the Heater-AC Control Assembly, the switch isolates all the functions from ground when in the "OFF" position.
I'll study this a bit more tonight.......imp

That's why I think it could be fixed right fairly simply, I don't want to hack a bunch of stuff up and try to remember what I did if I have a problem later. It seems it functions like it is supposed to, just opposite when it comes to the clutch.