a/c and heat

Last night while my 99 caravan 3.8 awd was idleing I noticed that it had an intermittent loss of power(idle would drop and interior lights would dim and rpm's would lower)and I heard a rattling noise that sounded like the fan was loose,I looked at it today and found that the problem only happens when my heater is on and I noticed that the a/c compressor kicks on intermittently when the heater is on and a/c off,I believe that the rattling is coming from the blower motor but my first concern is taking care of the heater/ac problem.Any help will be greatly appreciated. Thanks

The intermittent loss of power when idling was your A/C compressor cycling on and off. What position was your vent switch in when this occurred? The A/C compressor will automatically start when the "Defrost" setting or the "Bilevel Defrost" setting is selected (with the knob in the extreme clockwise positions). In all the other settings, A/C operation requires the A/C or "snowflake" button to be pushed. Remember, whenever you select "Defroster" on the vent control, the A/C compressor will run. We have owned our 1998 Town & Country LX AWD for six years and my wife still does not understand why the car gets cold when she turns on the "Defroster".

As for the rattling noise, I suspect one or more of the fan belt driven accessories is worn or loose. We experience the same thing in our T&C, as well. This is most pronounced when the engine is idling in gear with the A/C on. Hard to get out and stick your head under the hood under these circumstances. So far, I have replaced the water pump (it started leaking) and both the tensioner and idler pulleys, without a cure. This leaves either the A/C compressor, alternator, or power steering pump as the culprit. But nothing obvious sticks out. Good Luck with your Caravan.

Thanks alot KManiac that helps alot I didn't know that the compressor runs when on defrost,as far as the rattling I have tracked it to the blower motor,it only happens when I turn the fan on.Thanks again I was beginning to think I had yet another module going out.