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Ask A. Penland Your Own Question
A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Mercury
Satisfied Customers: 6206
Experience:  ASE Master Certified. ASE Gasoline Engine Performance Certified,Ford Senior Master Technician
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I have a 97 mountaineer that I'm having intermittent ac

Customer Question

i have a 97 mountaineer that I'm having intermittent ac problems. It was working on max ac then i switched to regular ac and quit working. i thought maybe low on freon so had mechanic refill and also place dryer. still have same problem after. weird. took back to mechanic. checked relay switch seemed ok, replaced anyway. still sometimes when i switch from max to regular clutch won't engage. my mechanic seemed to think it could be control unit on dash. i can get used one on ebay and replace but hesitant thinking these are only like on off switches but he said they have some computer controls in them that could go bad????
Submitted: 6 months ago.
Category: Mercury
Expert:  A. Penland replied 6 months ago.
I need to know if you AC controls are digital with a thumb wheel to control the fan speed or are the AC controls just three knobs?
Customer: replied 6 months ago.
Three knobs
Expert:  A. Penland replied 6 months ago.
Do not replace anything yet.The problem is either caused by the AC control panel, (3 knobs) or the engine computer (PCM). Your mechanic will need to check and see if power is taken away from the AC relay in the fuse box under the hood at pin #30 or if the PCM is taking away the ground signal to the relay at pin#85 when the AC controls are switched from MAX AC to Normal AC. Show him the diagram below.
Customer: replied 6 months ago.
It doesn't just happen when I switch from norm to max. It will also stop even if I don't turn any knobs
Customer: replied 6 months ago.
it's random. Sometimes it will run for two minutes then just stop and sometimes ten minutes before it stops.
Expert:  A. Penland replied 6 months ago.
Do you have to be driving it or will it do it at idle in park.
Customer: replied 6 months ago.
It will also do it in idle.
Customer: replied 6 months ago.
I was almost thinking maybe a loose wire connection somewhere
Customer: replied 6 months ago.
Are there any kind of computers in the control knobs
Expert:  A. Penland replied 6 months ago.
It very well may be, but the test I posted earlier will tell us what direction to look. The WOT AC RELAY controls the power to the AC compressor. It gets power from the AC controls and ground from the PCM to turn the relay on to send power to the AC compressor. No computer in the control knobs.

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