T5 Airconditioner stopped

[BrianJ]

I have just spent the last week getting my airconditioner fixed on my 2006 96kw 5cyl diesel kombi beach. It has done 75000km and was working one day and no cold air the next.

Traced to a faulty denso compressor, which appear to fail frequently and no one knows why, except it will be a minimum of $2000 to repair. It seems the T5 compressor turns all the time, and the output is controlled by control valves which can control it from 0 - max output, unlike the magnetic clutch traditional method. The drive method is interesting as it is driven from the output of the power steering pump, via a gates coupling, then a ratchet hub, then a strange coupling in a black metal housing, then into the compressor input shaft.

The old compressor was sent to a expert shop where they found that the input shaft spline was stripped clean allowing the input hub to spin. When they drove the input shaft on a test bed, there was also no output, so it was concluded that the control valves were stuffed, but the compressor did not explode as there was no debris in the oil, thank goodness, otherwise everything must be flushed or replaced.

It was also found that the ratchet hub was siezed, so it was replaced at $280, but the gates coupling was still good at 75000km. Nobody knows why this happened, or whether it will happen again, just drive with your fingers crossed, and it is happening on many big brand name cars for similair unknown reasons.

This is my guess: Something goes wrong with the control valves and the compressor suffers hydrolic lockup similair to a diesel with water in the cylinders, then the spline strips, which is most likely made as the weak link to save the drive line, and all output is lost. Problem is that nothing can be salvaged as the main shaft is stripped. Its good money for the repair shops who probably don't care why they fail as long as they do fail so they get plenty of money.

Anyone else seen this or have any clues why it is happening?

Brian

[Splitn]

Brian,
It's the seized " free wheel " which has caused all the damage.
But the gates coupling should have sheared but didn't.
Mine damaged the power steering pump when my free wheel seized, and the gates coupling didn't shear also. It also was at about 75000km mark.
The free wheel allows the air-con compressor to continue to rotate however small or large amount required once the engine comes to a complete stop, or when the air-con is off or not under load.
When I ordered the new " free wheel " using the Volkswagen part no. on the failed unit , the replacement part that came has been redesigned and was quite different.
Perhaps Volkswagen were aware of the problem.
On a good note the air-con has worked well ever since.

Cheers Greg

[BrianJ]

Thanks for your thoughts on this, the only feedback I got on the freewheel was that it was a black one whereas the original was plain aluminium. Lets hope that was the reason.

Brian

[Splitn]

Thanks for your thoughts on this, the only feedback I got on the freewheel was that it was a black one whereas the original was plain aluminium. Lets hope that was the reason.

Brian

Brian,
My failed freewheel was also the alloy type, and was replaced also with a black one.
It was some time ago when it was changed but I think the bearing seemed to look a bit larger in the new part.

Greg.