Aircom sometimes not cooling

kj75 · **Posted:** Wed Feb 03, 2016 12:37 am

Hi all,

I have a 2006 Jeep Cherokee Diesel in Australia, and sometimes on occasions the A/C just blows normal air (not cold) even though it is turned on.
At a later stage (5 to 10 minutes) the A/C just starts working again. I cannot replicate the problem every time. On some days it just works without any problem.

A month ago I took it in to a mechanic who replaced the A/C fluid but the problem has since re-occurred.
The engine seems to be louder (sounds like rattle) when the A/C is on and I was thinking it could be a faulty A/C clutch.

Any ideas would be welcome.

KJ75

papaindigo · **Posted:** Wed Feb 03, 2016 10:03 am

Rattle is likely a bad alternator decoupler clutch (see if serpentine belt bounces a lot a idle-it should barely twitch). Intermittent AC operation given that you have done the fluid then I'd suspect an AC sensor.

Billwill · **Posted:** Thu Feb 04, 2016 11:26 am

I see that you posted this on the ausjeep.com forum as well...I recently signed up there as the Export CRDs have some changes compared to the USA models.

I agree with papaindigo that the noise may be your alternator de-coupler.

The fact that your cooling problem is intermittent would point to a loose wire somewhere or maybe a suspect aircon relay.
Easy thing to do is to swap over the aircon relay in the relay box under the "bonnet" with an identical next to it.

Also check the Black grounding wire on the compressor is clean and tight.

kj75 · **Posted:** Thu Feb 04, 2016 8:03 pm

I will check the relay by swapping it with another and see if I can see a loose wire near the A/C.
Can the alternator de-coupler be changed with minimal effort and what would be the part number ?

I have previously changed the alternator de-coupler, so hoping the A/C de-coupler is not much more difficult.

Billwill · **Posted:** Fri Feb 05, 2016 2:12 am

kj75 wrote:

I will check the relay by swapping it with another and see if I can see a loose wire near the A/C.
Can the alternator de-coupler be changed with minimal effort and what would be the part number ?

I have previously changed the alternator de-coupler, so hoping the A/C de-coupler is not much more difficult.

The aircon does not have a decoupler ie. a one-way clutch such as the alternator uses.
It has a circular flat friction pad which is driven by the serpentine belt. There is a small air-gap between it and the compressor assembly which also has field coils inside it. If the aircon Relay is de-energized then the air gap is maintained and the clutch disk spins freely while the compressor stays still. When the relay applies +12 volt to the coils inside the compressor...the clutch pad is magnetically drawn to the compressor drive side and the compressor now turns. You can hear the aircon clutch kicking in and switching off...if the refrigerant is low or the sensors for the refrigerant or failing then the clutch kicks in less frequently. You can force the clutch to kick in by removing the aircon relay and jumping pins 30 to 87 together inside the relay socket but only do this for a very short time because if the refrigerant is low then you will damage the compressor due to lack of lubrication!

You can always add a seperate grounding wire from the compressor body to a clean chassis point nearby and see if that helps.

The clutch assembly itself can be replaced without touching the compressor or releasing the coolant...do a search for the process....you have to add or remove shims to get the correct air-gap. There are also cases of the compressor bearings failing.

What papaindigo is refering to though is that a failing alternator decoupler can enable the Serpentine belt to run smoothly if the aircon is disengaged. When the aircon kicks in though the failing alternator coupler can not handle the extra load of the aircon and causes the serpentine belt to jump up and down causing a noise and early failure of the belt tensioner or belt.

So this could make it look like the aircon is causing the noise and jumping belt but it actually a failing alternator decoupler.

When did you last have the decoupler changed? Was it OEM? A better coupler to fit is the Litens 920834 as it is greased and sealed as compared to the dry open OEM unit. Your Ausjeepoffroad.com site should have more info for you as to where this can be obtained. :wink:

kj75 · **Posted:** Sat Feb 06, 2016 9:08 am

The alternator is brand new and barely 3 months old. The make of the alternator is OEX and came with 3 years warranty. I was advised this was a very good quality alternator. The problem hasn't occured again, so I may have to wait until it gets worse.

Billwill · **Posted:** Sat Feb 06, 2016 1:00 pm

kj75 wrote:

The alternator is brand new and barely 3 months old. The make of the alternator is OEX and came with 3 years warranty. I was advised this was a very good quality alternator. The problem hasn't occured again, so I may have to wait until it gets worse.

I could not survive one Summer day without my aircon....the ground for the aircon is located behind the starter solenoid...you should see it from under the Jeep. Check if it is tight and clean...that location can get a lot of water sprayed up there. bad grounds keep vehicle electricians in business. :wink:

ibedonc · **Joined:** Mon Feb 12, 2007 2:40 pm **Posts:** 236

could be the pressure switches also , I had mine do this , stopped when both were replaced

kj75 · **Posted:** Tue Mar 15, 2016 10:46 am

The issue seems to have been the AC relay.
I simply switched the AC relay with the Viscous heater, and the AC has been working OK.

geordi · **Posted:** Tue Mar 15, 2016 12:22 pm

Bonzer for an easy fix!

I doubt you'll have much need for a viscous heater down there too. Does it ever snow?

graycenphil · **Posted:** Mon Aug 15, 2016 1:35 pm

Where exactly are the AC and viscous heater relays? I'm having a similar problem.

Thanks.

geordi · **Posted:** Mon Aug 15, 2016 2:07 pm

Relays are in the "power distribution center" box that is right in front of the battery.

Note that there are TWO pressure switches in the AC system. The low switch on the drier cannister by the coolant tank and the high switch on the AC line just inboard of the battery and below the alternator.

graycenphil · **Posted:** Mon Aug 15, 2016 2:25 pm

Thanks Geordi.

Aircom sometimes not cooling

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