AC compressor on when heater on

[Dannieb1973]

Why does my AC compressor kick on whenever I turn my defroster on?

 

[Snoranger]

It’s supposed to. AC helps dry the air and defrost the windows faster.

 

[Dannieb1973]

It’s supposed to. AC helps dry the air and defrost the windows faster.

Okay, thank you. I just wanted to make sure everything was okay.

It’s supposed to. AC helps dry the air and defrost the windows faster.

 

[Dannieb1973]

I do have one more question. I'm not too knowledgeable on dealing with air conditioning So please bear with me... I just put one can of freon in and My compressor only kicks on and then goes right back off again, it doesn't stay on for longer than a second. Is this because I still need to put more freon in?

 

[RonD]

Maybe............................but the AC system has 2 pressure switches, a low pressure and a high pressure switch

These both have to be closed for compressor clutch to stay engaged
In 1997 the AC control in the cab sends 12volts to the low pressure switch, which then passes the 12volts to the high pressure switch which then passes the 12volts to the compressor clutch relay that powers on the clutch

Cab control(12v)-----------------switch-------------switch---------------relay---------clutch

The clutch is engaging so at rest both switches are closed, but just after clutch activation one may be opening, may be the lower pressure switch if freon is low, but could be high pressure if there is a blockage in the system


AND..............the clutch itself may be bad, not uncommon on Fords, the clutch is basically an electro-magnet, the 12volts causes it to become a magnet and pull the clutch plate in to spin compressor, there is an "air gap" that needs to be close enough to allow the magnet it pull in and hold the plate but not too close or it will rub on the spinning plate
If gap is too wide plate will pull in and then release

Google: Ford AC air gap

 

[19Walt93]

I wouldn't just blow freon into it. If it's low it has a leak, once that's located and fixed you should pull a vacuum on the system for 10-20 minutes to make sure it holds, then charge it. The vacuum will also remove air and make the system work better.