T5 Caravelle 4Motion 2.5 Diesel 2007 Air cond unit clutch

[jjhobart]

The one way gear on the air cond unit clutch failed and was replaced.
All good for maybe a week when the the gear seized and chewed out the toothed drive belt.
So I replaced it and the new one also seized as did the next replacement.
What is going wrong? The clutch units are after market from 3 different suppliers. All worked for a short time.
Any ideas?
Thanks John.

[BrianJ]

I assume by 'seized' you mean the coupling is solid and don't ratchet anymore ?

It sounds more like the compressor has seized and that is damaging the gates coupling or the ratchet coupler. When my 2006 compressor seized it stripped the spline off the input shaft to the compressor, which I later found out was incorrect. What it did was strip the spline out of the coupler and left the metal in the compressor shaft spline so it looked smooth. It still needed a new compressor to fix it.

[jjhobart]

Hi Brian
It is the metal ratchet gear that seizes and strips the toothed belt (gates coupler?).
I can spin the AirCond compressor easily by hand.
John

[BrianJ]

Hi Brian
It is the metal ratchet gear that seizes and strips the toothed belt (gates coupler?).
I can spin the AirCond compressor easily by hand.
John

But even if the ratchet seizes, if the compressor is still turning then there will be no force of the gates coupling. My suspicion is that the compressor seizes sometimes. I have to admit it is very odd.

[jjhobart]

But even if the ratchet seizes, if the compressor is still turning then there will be no force of the gates coupling. My suspicion is that the compressor seizes sometimes. I have to admit it is very odd.

Hi Brian - I finally got around to removing the clutch unit today and found that this time the rachet gear was not seized (an assumption from previous experience) rather the gear free-wheels in both directions. Point taken on gates coupling being stripped. I guess should the compressor seize temporarily then one of two outcomes proceed - the gates coupling strips or the rachet lock in the drive gear breaks.
Regarding the compressor - is it likely it can seize temporarily? I can manually spin it with very little pressure - compressor unit is still in the vehicle and has not been disconnected from the still gassed air-conditioning system.
Regards
John

[BrianJ]

I have not heard of a compressor seizing momentarily then becoming free, but I can only tell what I have experienced with mine. I know that the compressor is continuously driven and the output is controlled by a valve in the unit and my second compressor lost output due to the valve becoming blocked. This was explained to me by an experienced air-con shop which fitted my third compressor many years ago and it is still going. I also have not heard of the coupling becoming free wheeling in both directions, and all the ones on mine that have failed through the years have become locked in both directions so maintained drive. When the do this it can destroy the compressor, and i recently had to replace the one on my alternator as it was making a hard knocking noise due to being seized and probably would eventually kill the alternator. My only thought in regard to temporary seizing of the compressor is that you can only test it when it is at its lowest output, a full test would be able to test if it is tight when the control valve tried to run it at full output. I think these still work by controlling the piston travel by moving a wobble plate, who knows what happens when the pump pistons try to reach full travel, could one be hitting something lodged in the cylinder. if that happened it would temporarily lock the compressor but be free when you turn it by hand. All these ideas are just thoughts on my part as I can't prove anything. If you are unable to have the compressor fully tested then it might be worth getting the opinion of an expert.

[Greg Roles]

How old is the spragg clutch - the cog wheel thingo? They should be replaced about every 150k thou or less to save yourself the heartache. Pain to get to, but pretty easy once in there. Do them both also, there's two of those bastards in there!