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AC cut out switch adjustment procedure

Jim1941 on Fri August 12, 2011 1:28 PM User is offline

Year: 2002
Make: Mercury
Model: Grand Maquas
Engine Size: 4.6 V8
Refrigerant Type: R134a
Ambient Temp: 85
Pressure Low: 45
Pressure High: 145
Country of Origin: United States

Hi, I am replacing my compressor because it started making a winey noise and later the clutch burned up. The relay stuck and I drove about 100 mi not knowing the compressor was engaged with the sys off. I assume the damage to the compressor was caused by hi pressure and freezeing up and think the cut out switch should have protected the compressor.
Does anyone have a idea why the compressor was damaged? The system still cools ok. I am buying a new cut out switch and plan on installing it when I replace the compressor, Acculator and a new orifice. Can one of you very experienced people advise me on how to install the switch? I have heard some are adjustable. If mine is adjustable how do I adjust it. Also is there some other switch that perhaps failed causing the damage to my compressor. I assume that the swatch plate and slippers are scared causing the noise. There is a pressure switch on the system but I don't know what it function is, maybe hi pressure cot off. It is pretty expensive and I don't what to replace it with out knowing it is bad. How can I test these switches?
Also can I flush with mineral sprits and then follow up with a A C flush? Thank you for any advice.

mk378 on Fri August 12, 2011 2:00 PM User is offline

You said the relay was stuck, if that was the problem just replace the relay. The switches are before the relay, so they probably worked like they should trying to stop the compressor-- but the relay was stuck-- so it didn't stop.

The condenser catches most of the debris from a blown compressor, it should definitely be replaced here.

Jim1941 on Fri August 12, 2011 2:46 PM User is offline

I Replaced the relay the next morning when I saw the compressor would not stop. The compressor still had the whiney noise and a week later on the road the clutch must have slipped and got really hot. after it cooled it engaged but it got so hot the bearing was damaged and is very nosey. A few weeks before all this, I think the evaporator was freezing up because the vent volume would go down when the fan was set to low. I would turn the sys off for 5 minutes and it would start blowing at full volume and if I kept it on hi fan it never happened.
I think the clutch failed to engaged because of hi milage (100,000) and probably the air gap opened up. I had just passed a slower car had hi engine rpm when the clutch failed to engage.
I though it froze up again but later found the clutch bearing was damaged. The system still works ok and appears to blows very cold air but the pulley bearing is noisy and the compressor wines. I don't know why the system was freezing at low fan settings (I saw the accumalar with 1/4 inch of frost one time) I also observed that the compressor would only disengage for about a second with the engine at idle and low fan with a 75 degree ambient temp.
Any thoughts about the freezing? And what about the cut out switch.
How can I check the condenser for compressor junk?
Sorry this is so long
Thanks for any advice.

JJM on Fri August 12, 2011 8:30 PM User is offline

Replace the CPS at the accumulator. No need to test or adjust, clearly the switch is stuck closed or way out of whack.

This is one the easiest and most inexpensive A/C fixes - about $20 even if you get the switch from a Ford dealer - just disconnect the connector and unscrew the switch from the accumulator. Reverse procedure to install. You don't even need to discharge the system.

To confirm the compressor is disengaging, run the engine at 2,000 RPM with the A/C on the lowest blower speed. Compressor should start to cycle (21-23 PSI).


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