Infuriating 405 air conditioning issue

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carlo14
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Joined: 29 Apr 2009, 08:47

Infuriating 405 air conditioning issue

Post by carlo14 »

Hi all.

Could anyone shed any light on what might be happening here.

I have an erratic and very annoying problem with my 405 2.0 petrol's air conditioning, especially annoying as it is my daily driver! It is a 1995 Mk II automatic.

Basically it works some of the time, not others, and has been going on for about a year. It may work fine for a few days, or more likely work fine for half an hour then just stop working. The A/C light on the heater control comes on and stays on. It has been gassed last Autumn but that made no difference; sometimes it worked sometimes it didn't. When it works it is ice cold and can work for the full hour or so I use it, and then the next day or so. More probably it will work for a few minutes then cut out, and then quite possibly cut back in again a few minutes later (or not). Sometimes it won't work for days. I did find sometimes if I gave the revs a blast it would kick in, but that doesn't work all the time. You can clearly hear the compressor cut in when it works, and remain silent when it doesn't. It has been with two specialists on more than one occasion, once I left it there for a week, and of course behaved it perfectly then.

The heater fan and cooling fans work fine.

Any ideas/troubleshooting I could try?

Cheers!
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RichardW
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Re: Infuriating 405 air conditioning issue

Post by RichardW »

By the sound of it the compressor clutch is not working - either this is a fault with the clutch, or it's an electrical feed fault. I would rig up an LED across the compressor contacts, then when it plays up you can see whether the power is there to pull the clutch in or missing. This will then give you a pointer whether you need to look at wiring, or if it's an issue with the clutch itself.
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GiveMeABreak
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Re: Infuriating 405 air conditioning issue

Post by GiveMeABreak »

Second that ^ The clutch component of the compressor can wear over time and to be honest, at nearly 30 years old if on the original, that's not bad going. I needed a new compressor at only 7 years old.
carlo14
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Joined: 29 Apr 2009, 08:47

Re: Infuriating 405 air conditioning issue

Post by carlo14 »

Thank you for those, that sounds very plausible.
ozvtr
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Re: Infuriating 405 air conditioning issue

Post by ozvtr »

A common problem is the metal friction surfaces of the clutch plates wearing away. The clutch electromagnet can only pull the two plates together from a very small distance. Once the plate surfaces wear by a small amount this distance becomes too great for the electromagnet to work. This is a gradual process and causes the compressor clutch to fail at random times but tends to get worse and worse over time.
There are shims on the input shaft to set the gap of the plates. Typically they look like very thin washers. If that is the problem, the plate gap can be re-shimmed very simply.