XJ A/C pump

That's a pretty wierd symptom, but I doubt if replacing the clutch or compressor would fix it. Sounds like a problem in the control circuitry.

I would start by disconnecting the wires at the clutch and hooking up a voltmeter to see what is happening - maybe you are getting stray voltage high enough to momentarily lock the clutch. Also check the ground while you are at it.

These are guesses, but you have to start somewhere....

ps: get a wiring diagram and a decent digital volt/ ohm meter.

John Davies Spokane WA USA

Just a simple thought: you say that the A/C is off, but could it be set to defrost (front window upper dash outlets)? The A/C compressor will also run (along with the electric radiator cooling fan) when the HVAC control is set to front window defrost. The purpose is to dehumidify the air and hopefully defog the front window faster.

Other than that, since the clutch is electrically operated, I'd whip out a tester and see if it is being energized when you hear it engaging. If so, then you probably don't have a mechanical failure. Something is "telling" it to energize.

Just a guess...

-John

Overpressure? If the system overpressures, I believe the clutch automatically disengages until the overpressure clears. It could be due to a blocked line or orifice.

Approximately 10/22/03 07:51, CrazyJ uttered for posterity:

By any chance is the defroster on? If so, this is normal operation.

Do the revs kick up for about a sec and then drop back down? Mine does that when it's cold. I'm not sure if it does it when it's warmed up, I just assumed that it was a way for the engine to warm up faster. Let me know if you find out anything. I think mine kicks up more often then every 30 seconds but it's probably the same.

Mort

CrazyJ wrote:

Yes, the rev's do kick up for a second. The defroster is not always on when this happens, and it does happen after driving for a while (aka it is already warmed up).

Thanks again,

Jason

Sorry, my bad (was going on info from the wife). I tested this out last night - it only happens when the defrost is on, so according to John Sevey and Lon Stowell, this is normal. Good to know, thanks guys.

Jason

disengages.

Cool!

Or should I say, "Less humid". :)

By the way, your 2000 probably has two "defrost" positions on the HVAC selector knob: defrost, and defrost floor.

That means that the A/C compressor will/should operate on: a/c, max a/c, defrost, and defrost/floor. That leaves (I'm recalling from memory here) off, vent, and heat/floor as the _only_ positions where the compressor won't operate.

You probably already found this out, but I thought that I'd clarify -- since my original post wasn't all that clear...

-John

Thanks, I was starting to think that I might have a problem on my hands. From what I can tell it's only happening when it's on defrost or when the AC is on.

Mort

John Sevey wrote: