Engine surging when heater/AC is on

I have a 2001 Limited that I just got a couple months age. I have noticed that when I have the AC or heater on that the genine gets loaded and the rpm drop about 100rpm's or so. For about 1-2 seconds, the revs go back up, then drop back down for about6-7 seconds before starting the cycle over. I was just wondering if this is normal. I know when you turn on an AC unit, like in my old ranger, the engine is using the compressor and will load the engine. It never cycled like the jeep though.

Anyone have any opinions?

Thanks
C

Refrigerant leak causing the compressor to short-cycle?

Dunno - my AirCon XJ's have always done that, so I figure it's the compressor clutch cycling to keep the coolant pressure up. Why? How do I know - I'm not an HVAC tech...

This is, of course, merely a guess. Any relationship between this guess and exstablished facts is purely coincidental, and should be ignored...

5-90

If it's the compessor, would it still cycle when the Heater is on?

In you non-HVAC tech opinion. :laugh:

C

Why not? I seem to recall reading somewhere that AC-equipped vehicles used the aircon system to remove moisture from the blower system when the defogger is on, and the defog and heater are related, so it makes a perverse sort of sense. I would also expect that, it being a pressurised system, it would want to maintain coolant pressure for "on-demand" use.

You can try pulling the plug on the compressor clutch - probably easiest to do at the receiver/drier (there is a pressure switch on top of it that is a low-pressure cutoff for the compressor clutch.)

5-90

I don't have the wiring diagrams for the 2001 but the a/c only comes on in the defrost mode in the earlier models. Of course the easy thing to do is look under the hood with it on and see if the a/c clutch engages when you have only the heater on. I'll have to let someone with a later model tell you if that is normal. :wierd: