2002 Ranger AC Problem

[deep3]

The truck at Idle is when the ac kicks off and on.
Checked at 1500 rpm and coolant is good.
The clutch engages then dissengages right away at idle.
What could be the problem here?
At 1100rpms and up the clutch runs constant.
thank you

[dozer]

Hello, I'm thinking when you say coolant you mean refrigerant right? I would guess low refrigerant because as pressure builds the clutch remains engaged that would make sense. When rpm's and pressures are low the compressor will cycle if the low pressure switch tells it to, if the charge is too low the sensors will tell the compressor that there is "no charge" and in an attempt to save itself it will cycle off a second after it starts, but as you increase rpm's you also increase running pressures which will keep the compressor running. If you haven't already, use the proper gauge manifold and take pressure reading's. Also your compressor is designed to cycle on and off as more or less cooling is needed. Todays compressors run much more efficiently than the older ones did and it is normal for them to cycle but they will usually will run for a few seconds before doing so. Hope this helps. BTW what engine do you have?

[deep3]

Is there any other reason that would cause the compressor to click off and on other than the refrig being low?
thanks

[dozer]

There are a couple of other things you can look at, the first being your low pressure switch. As I mentioned these switches are designed to disengage the compressor during a "low pressure" situation, however, like any thing else they've been known to fail, an easy way to check for this is to eliminate the switch from the circuit entirely by jumping it out. The second thing I would check for is a possible blockage, you can do this by recovering the charge and pulling a good vacuum on the system then replacing the filter/dryer and recharging. I do not know what motor you have so it is difficult to make a positive diagnosis for your particular problem but it sounds like either there is a low pressure switch malfunction or a low system charge. Give the low pressure switch jump a try and see what happens if the comp runs then you know that you must replace the switch, I've also seen temperature switches give false readings as well, unfortunately there a lot of variables here so it comes down to the process of elimination.