What could be constantly kicking on and off at idle?

logom · **Joined:** Mon Apr 05, 2010 1:44 am **Posts:** 22

After doing some searches I have found nothing on this issue. When my '06 CRD is running at idle, there is a slight clunk that happens every 5 seconds. This sound corresponds with a slight drop in idle. My guess is that something seems to be kicking on and off constantly. I only notice it at idle. If it is happening at other rpms I don't notice. It is really annoying and I also don't want this problem to lead to other problems. Any ideas and suggestions would be greatly appreciated.

Thanks!

RJM · **Posted:** Tue Feb 07, 2012 7:31 pm

Air con. comp.

spitfire36o · **Posted:** Tue Feb 07, 2012 7:35 pm

Its most likely the viscous heater. There is a small coolant heater on the top left corner of the serpentine belt route. This helps heat up the coolant to bring the cabin temp up quicker in the winter. You can open the power box in front of the battery and pull the relay to disable the clutch pulley from engaging.

logom · **Joined:** Mon Apr 05, 2010 1:44 am **Posts:** 22

Thanks for the suggestions. I have also been thinking that it has something to do with the AC compressor. Could this mean that the AC compressor is bad? The AC works just fine and no matter whether I have it on or not the sound still happens.

I will check the viscous heater as well. If I pull the relay that will tell me if it has to do with the viscous heater. If it does, what would I replace? Could this problem just be a bad relay?

RJM · **Posted:** Tue Feb 07, 2012 7:51 pm

Its normal, turn heat control to the off position and it will stop.

RJM · **Posted:** Tue Feb 07, 2012 7:53 pm

Cycles automaticly in the last three positions. There is a mod to bypass it.

logom · **Joined:** Mon Apr 05, 2010 1:44 am **Posts:** 22

Last three positions for the blower motor? Like all three positions except for really high? How does the mod work? Great suggestions by the way!

RJM · **Posted:** Tue Feb 07, 2012 8:11 pm

Not the fan speed, but the directional control for the air. No matter what the temp is set at, air on or off, the AC comp will come on (very annoying). If I remember correctly it comes on with the defrost or any combo using defrost. Mine is modded so I'm not sure.

RJM · **Posted:** Tue Feb 07, 2012 8:12 pm

There is a writeup for the mod. with pics. I just can't find it.

spitfire36o · **Posted:** Tue Feb 07, 2012 8:27 pm

logom wrote:

Last three positions for the blower motor? Like all three positions except for really high? How does the mod work? Great suggestions by the way!

-The viscous heater cycles on and off until the coolant temp reaches 162* or the air temp reaches 54*
-The A/C compressor will cycle on and off when the position selector is on defroster and also floor/defroster
viewtopic.php?f=5&t=63145

logom · **Joined:** Mon Apr 05, 2010 1:44 am **Posts:** 22

Wow, thanks! I'll try setting the selector to vent and see if that works. If it does I'll be REALLY happy!

papaindigo · **Posted:** Wed Feb 08, 2012 8:14 am

Go to viewtopic.php?f=5&t=63145 and scroll down to my post for 2 options that address AC cycling on/off when the AC button is NOT on.

As I recall the AC is activated, regardless of AC button position, when the vent selector is in Floor, Mix, and Defrost modes mainly for the purpose of reducing humidity which makes some sense in Mix and Defrost but why it's done for Floor escapes me. I routinely use Bi-level so it doesn't matter to me.

RJM · **Posted:** Wed Feb 08, 2012 10:19 am

it also keeps the oil moving around in the winter to prevent seal failure.

logom · **Joined:** Mon Apr 05, 2010 1:44 am **Posts:** 22

Thanks for the tips! I'll be able to give them a try tomorrow.

logom · **Joined:** Mon Apr 05, 2010 1:44 am **Posts:** 22

Problem solved! Thanks for the help guys!

CHessMaster · **Posted:** Tue Feb 14, 2012 10:08 am

RJM wrote:

Cycles automatically in the last three positions. There is a mod to bypass it.

A/C compressor bypass/control mod:
viewtopic.php?p=180099#p180099

OhmegaMike · **Posted:** Wed Feb 22, 2012 1:42 pm

You can also just pull the fuse for the A/C compressor. It's in the fuse box under the hood. That's what I did until I find time to mod the heater control...

What could be constantly kicking on and off at idle?

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