something at idle pulling a load for a second

[dkmcgowan]

When I sit at idle, I can hear something every couple of seconds pulling load.  It sounds like if you barely turned the steering wheel and the power steering pump started working for a second.  So this would be like if every second or two you barely moved the steering wheel and then moved it back.  I can hear the load happen and the idle just barely drops, then it goes back.

 

I have replaced the belt, the power steering pump, the idler pulley, and the water pump...

 

So on the pulley that just leaves the fan clutch and the AC...

 

When I turn on the AC it seems to stop, so it seems to only be when the AC is off.

 

Any chance the clutch on my AC has some drag every once in awhile even when off?

 

Any other ideas?

[HOrnbrod]

Easy to check - unplug the A/C clutch connector or pull the clutch relay and see if it goes away.

[Eagle]

If you have the heater set to defrost, it still cycles the a/c, to dry out the air it blows at the windshield.

 

Another possibility is alternator load, when the fuel pump kicks in and shuts off.

[DirtyComanche]

I'd personally guess alternator.

 

As said, pull the connector for the A/C clutch.

 

If it's still there, I'd pull the connector on the alt.

 

If it's still there, well, it ain't either of those things. :laughin:

[dkmcgowan]

It's a new alternator, not reman, but that doesn't mean much...  It's charging great and when I see the load happen, my voltage doesn't go down.  I will test both this weekend though.  If the clutch is bad on the compressor, would unplugging tell me anything?  Couldn't the clutch not disengage sometimes even when unplugged causing something like this?

 

I have some additional info though.  When I have the AC on, so the idle goes up a little, it smooths out and I don't feel the load every couple of seconds, even when the compressor is not running...  So as long as it's in the AC switch mode I don't feel it, no matter about compressor being on/off.  Weird right?

 

Also, when I'm driving and accelerating with the AC on, if the compressor is off and I'm accelerating and it then cuts on like it does every few seconds, I lose power for a second.  Is that normal?  You can feel the compressor cut on and the engine lose power for half a second, then you keep on going.  I've never had a car where you could feel the compressor cut on like that.

[HOrnbrod]

The compressor clutch coil has a diode wired in parallel to it. The purpose of this diode is to protect the electrical system by shunting any voltage spikes to ground when the A/C compressor turns off and on. If this diode goes bad it could cause the A/C clutch to energize randomly.

[dkmcgowan]

It looks like it would be pretty easy to replace the clutch, but I cannot seem to find one anywhere...  I found some new mopar units, but they cost twice as much as an entire compressor with the clutch...

[HOrnbrod]

Another possibility is alternator load, when the fuel pump kicks in and shuts off.

??  The fuel pump runs constantly when the engine is running, it doesn't kick on and off........

[A-man930]

 

Another possibility is alternator load, when the fuel pump kicks in and shuts off.

??  The fuel pump runs constantly when the engine is running, it doesn't kick on and off........

 

Yea that.

 

have you sat and watched the a/c compressor at idle?