A/c mode switch works backwards after v8 swap

[Ranger8]

After my 95 ranger was totaled by my 17 year old, I found a 98 with the 5.0 swap already done. Other than some minor issues it looks to be well done. One puzzling issue is that the a/c selector mode switch turns the a/c on and off in reverse order. It actually turns it on in the off position and off in the a/c max position for examples. The engine and harness is from a 99 mountaineer 5.0, the computer and transmission are from a 97. Everything else in the a/c system works like it should. In the on positions, it runs even with both pressure switches unplugged! In vent or heater positions I get cold air. Any suggestions?

Thanks,
Ranger8

 

[SoHK_alumni]

Hands down, the A/C control logic is the trickiest bit of a late Ranger/V8 Expo or Mountaineer swap.

As alike as the two vehicles are, the A/C control logic is very very different and blending the two systems is not plug and play.

In the Ranger, the A/C switch goes straight to the PCM, as does both high and low pressure switches. The A/C relay is always powered and the relay's coil is entirely controlled by the PCM. You select A/C at the dash and the PCM "lets" you have it if all conditions are met.

In the Explorer, the PCM is simply one more "switch" in series with the high and low pressure switches. You select A/C at the dash and the PCM can turn it off on WOT or over heat conditions.

Grabbing up a copy of the wiring diagrams (EVTM) for both your Ranger and the doner Explorer, sorting out how the conversion wiring was done then finding the fault in the conversion wiring is your best solution.

But, since the function is opposite of expectations, simply changing the wiring at the A/C clutch coil relay from NO to NC might (might) be all you need. The concern is that in the Ranger, the common pin between the NO and NC pins is always powered and the NO/NC swap might leave the clutch energized even when the engine is off -- you'd need to pull the fuse for the clutch and round a jumper wire from the dash control to the relay.

 

[Ranger8]

Thanks SoHK

I had attempted to switch the relay wires this weekend but was unsure which wires to change. I hadn't considered the clutch possibly staying energized with ignition off. I can install a switch if needed. At least I'm closer than I was.
Thanks again
Ranger8

 

[SoHK_alumni]

Should be a micro relay with 5 pins, three aligned one way, 2 the other.

Of the three in a row, the two outer are for the coil, the inner is the NC contact.

Of the other pair, the outer most is Common, inner is NO.

So? As long as the common is not powered with the ignition off, swaping NO and NC should do the trick.

If it is powered, pull the a/c clutch fuse and tie the violet colored wire from the a/c control panel into the non powered side of that fuse socket.

 

[Ranger8]

Got it!

The a/c clutch was powered with the ignition off after rewiring the relay. Ran the jumper and pulled the a/c fuse and everything works like it should! Should I put in an in-line fuse, or is it covered somewhere else? Thanks for the help. I have jumper wires everywhere now to test it out but will hard wire and clean it up tomorrow. One more gremlin dead.

Thanks so much for the help
Ranger8

 

[SoHK_alumni]

Sweet! No need to worry about a fuse, that violet wire is already fused in the doorpost fuse box.

In the Ranger, its a 10 amp fuse, a 15 in the Explorer. If the system blows the 10amp, opt for a 15 amp replacement.

 

[Ranger8]

Not quit like it's supposed to

Got to checking things and I assume I have bypassed the pressure switches. AC runs with them unplugged. Can I add them back into the loop somehow? Wired in series ahead of the clutch or relay possibly?

Thanks again,
Ranger8

 

[SoHK_alumni]

You've got a couple options to route in the pressure switches:

As I recall, the Ranger wiring has a wire go from the PCM, to the low switch, to the high switch to ground.

You can grab that PCM to Low wire, and use it either for the ground for the relay, or for the a/c clutch. If either switch opens, the clutch will de-energize.

Or, you can grab both ends of that circuit and route the a/c switch wire (that violet one from the dash) through both and then back to the fuse/relay box. Same result.

In both cases, (as is now) the PCM is fully out of the loop and won't have any control over the A/C system. Normally, the PCM will turn off the a/c under Wide Open Throttle or if it detects an engine overheat condition. In a perfect world, you'd include the PCM's ability to open the control circuit along with the pressure switches.

Not knowing how the Expo engine harness was grafted to the Ranger's makes it impossible to give more specific advice, sorry 'bout that. Did I not mention the A/C was the tricky bit in the swap?

I've often thought that Ford should darn well have built a V8 Ranger, would have been childs play for them and there's certainly a market. I love mine, but did all the work to build it. Not sure I'd have the courage you've shown by taking on someone else's work .

Good luck with it!

 

[Ranger8]

Almost there

I had planed on doing the swap on the Ranger my son wrecked. When I found this one at a good price, it made sense. I knew I would have bugs to work out. After the ac is done I have to figure out a cam position code. Not sure if it's from the swap or something else. New sensor didn't help and the synchronizer looks good and tight. I'll run the pressure switches from my violet wire and live with that. Thanks again
Ranger8