Climate Control Short

[Lunging Wolf]

I wonder if anyone has heard of this before. Recently I lost the ignition module in my 86 Mark VII LSC. The unit that mounts outside of the distributor. When I replaced it the car was running fine....until I turned on the air conditioning. After a few moments of running the air it starts running on 7 cylinders, (which might actually be a problem with the ignition module.) So I turned the air off, and after a few minutes it starts running clean again.

I tried an experiment where I didn't run the air at all for a month and never had a problem. After that I turned the air on again, and in just a few minutes it was running horrible again. I do believe there is a wiring harness that shares distributor wires, and the air conditioning compressor wires.

I should also mention that when I was flushing the cooling system recently, and turned on the heater to flush the heater core, I noticed the air conditioning compressor coming on and going off occasionally. The compressor shouldn't run with the heater on, should it? So, has anyone heard of a short in the climate control causing a problem with the distributor before?

One more tid bit. In the three years I've owned this car it only idles much smoother with the air conditioning on, and always suspected there was a problem in the climate control.

 

[Elessee]

running on 7 cylinders? ...meaning one cylinder isn't firing? How do you know that?

The AC certainly puts a noticeable load on the engine.. i can usually tell when it's on or off by the way the car accelerates.
I'd guess that load could cause the engine to run "horrible" if the car already has some sort of tuning problem.

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"....and turned on the heater to flush the heater core..."

How do you turn on the heater? I have climate control on this '88. There's no heater option. The system attempts to reach whatever temp you have selected.

"AC" seems to mean that it will "automatically condition" the car's climate with both heat and cold..
AC = "Automatic Climate" control? I dunno.

On my car, heat and cooling normally cycle on and off once the temperature I select is reached... a little AC.. a little heat. Your seeing the AC compressor cycling might be due to that.

Actually this is kinda annoying when, once in a while, I get a blast of hot air on a hot day, or cold air on a cold day.. Adjusting the temp a few degrees usually cures that.

 

[Lunging Wolf]

Thanks for the reply

No, this car normally runs like it did in 1986. It is an EXCELLENT running car. I've used the AC for 3 years, and it loses a little power, but this is nothing like that. I won't say for sure it's running on 7, but there is a SERIOUS degradation of performance. It runs EXTREMELY rough, and loses 75% of its power. I mean to the point it scares me that I might do mechanical damage. There has to be a short between the climate control and the ignition module. I was just wondering if anyone had any ideas where it might be.

 

[Elessee]

If it were me, I'd first suspect whatever changes were made around the time the problem appeared.

"...Recently I lost the ignition module in my 86 Mark VII LSC... "
Was the replacement module installed properly?
What caused the old module to go away? Does that cause still exist... alone, in a different form with different symptoms, or in combination with a new problem?

 

[OldSchool1]

Wire Woes.

No, this car normally runs like it did in 1986. It is an EXCELLENT running car. I've used the AC for 3 years, and it loses a little power, but this is nothing like that. I won't say for sure it's running on 7, but there is a SERIOUS degradation of performance. It runs EXTREMELY rough, and loses 75% of its power. I mean to the point it scares me that I might do mechanical damage. There has to be a short between the climate control and the ignition module. I was just wondering if anyone had any ideas where it might be.

You'll need to trace the wire from the top of the compressor back to the dryer switch on the fire wall. It ~may~ share a wire loom with your alternator wires behind the alternator. I cannot see it being a short though as this line is normally open until switched. If it were shorting to a live line then the compresso would be constantly on.

Your best answer would be to check the connector at the top of the compressor for full and steady voltage. All it does is pull in the clutch and should be constant when a call for cooling exists. Your next test would be a wiggle test. Be prepaired to remove some wire loomes and old factory tape

Our Climate Controls are powered through our ignition switches. How's your's?

Yes. Our compressors can run when the climate control is set anywhere between 60-85 degrees F.