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Vauxhall Omega Aircon

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Clive B 130/06/2018 21:45:39
43 forum posts
10 photos



Hi Guys

Is there someone out there that doesn’t mind helping me out, I’ve got a problem with an aircon compressor on my car and I don’t happen to have an inner cabinet parliamentary retirement pension so I’m having a go at repairing it myself in an attempt to keep the repair cost down.

I’ve included some photos and done a sketch as best I can to illustrate how the aircon should work.

Just to bring you up to speed the car went in for an mot and I was told the aircon clutch was loose and making a hell of a racket.

When I looked at it I was surprised it past the mot, the clutch had completely come off and was rattling around inside the aircon pulley, it was the only thing stopping it from falling onto the road, the screw and spacer had gone completely no doubt dropped off along the road somewhere, which brings me to the problem I’ve got.

I don’t know what the screw looks like, if you take a look at my sketch in view “A” it shows the aircon compressor coil and the aircon compressor pulley which has a shaft with external splines and a blind M6 tapped hole.

View “B” is the aircon compressor clutch with internal splines but it also has an M8 through tapped hole.

Whenever the engine is running the aircon pulley is also rotating being driven via a poly v belt which in turn takes its drive from the crankshaft.

The pulley simply rotates freely on the stationary aircon compressor shaft.

There is a fixed coil which the aircon pulley rotates around, there is also a gap between the faces marked xxxxx on the aircon pulley and the aircon clutch, this is usually set by a spacing washer.

If the aircon is switched off inside the car the coil is not energised so the gap between the pulley and clutch remains, but once the aircon is switch on an electro-magnetic field is created which draws the clutch along the splines until both faces marked xxxxx are in contact with each other, causing the clutch to also rotate with the driven pulley and because its splined onto the shaft, it then turns the compressor shaft thus in turn starts to pump refrigerant around the system.

That’s what is supposed to happen, right or wrong I fitted a screw an M6 screw through the M8 hole in the clutch tightening it into the M6 hole in the end of the shaft only to find I’d locked the whole thing up so the clutch is in constant contact with pulley so the aircon never switches off irrespective of if the coil is energised or not.

Question does anyone know how I can fix the clutch to the shaft without locking everything up but allowing it to float once the coil is energised.

I’d thought about putting a longer screw in so it bottoms tight against the bottom of the blind hole in the shaft but making it long enough to leave a gap between the underside of the head and the clutch.

The thing is I have never heard of a screw relying on being tight by having it bottom in a hole.

I also thought I could tighten it so far and using Loctite let it set, but then there’s always that nagging thought, if the Loctite fails I’ll have the same problem all over again.

Now there is just one last possibility I can think of, years ago there used to be different classes of thread fits for example if you screw a stud into something and you don’t want the stud to come out when undoing a nut, the thread on that end of the stud was different to the nut end, at least I think that's how it worked.  Having said that I can't imagine for one moment the car manufactures going to that trouble.

As to the M8 tapped hole in the clutch I haven’t a clue what that is for, all I know is it can’t be there just to make it look pretty.

Right guys that’s my tale, is there someone out there who can put me right on the problem.

How do I fix the clutch and allow it to slide along the shaft and what is the M8 hole for.

I hope I haven’t sent everyone to sleep who reads this post and to those who are still awake my thanks once again for any help you can offer.


Edited By Clive B 1 on 30/06/2018 22:35:29

vintagengineer30/06/2018 22:20:50
468 forum posts
6 photos

.The M8 is for jacking the pulley apart and the M6 should be a shoulder bolt.

Clive B 130/06/2018 22:46:12
43 forum posts
10 photos

Hello vintageengineer

Thank you for your reply, it may seem a daft question but why would the pulley need jacking apart, under normal operations ie aircon off, they are apart.

You also mentioned a shoulder bolt, I do know what one of those looks like but how would it fit. in my application?

If you have the time I'd sure appreciate a sketch, sorry if it seems straight forward to you.

Thanks once again for your help


vintagengineer30/06/2018 23:05:39
468 forum posts
6 photos

Shoulder bolts have a plain section that is larger than the threaded section.

Clive B 130/06/2018 23:19:24
43 forum posts
10 photos

Ok I understand the M6 threaded section will screw into the shaft and the shoulder will sit against it, but it doesn't seem to leave much of a shoulder if the plain section has to pass through the M8 tapped hole, if that is what you are meaning.

I'm signing off for tonight hopefully I can get it sorted tomorrow.

Nicholas Wheeler 130/06/2018 23:35:02
258 forum posts
13 photos

Clive, if you'd posted those photos on the Omega Owners Forum we could have advised what you're missing and what is damaged beyond repair a bit more satisfactorily. I would reiterate the advice there: you should be looking for another compressor. Which is a common part, and you've done the tricky part which is removing ityes

Clive B 102/07/2018 21:32:08
43 forum posts
10 photos

I did the sketch but had the headache of finding a website where I could upload the photos for free, I did use Photobucket which is no longer free and photos that have been posted on forums through them are no longer visible, what a bind that is.

I have tried a couple of breakers one being called without much success, I was thinking these Omegas are getting that old now especially the diesel I’ll be lucky to find anything.

So, I got to thinking why buy a compressor if it’s just a simple thing like a screw and spacer which has gone missing.

I have just received a message on the Omegaowners Forum from a guy who has told me the air gap spacers on the Astra and Zafira are between 0.3mm and 0.5mm, I’m not sure if the same applies to the Omega.

I’ve got to say to everyone on here who replied, I have just seen the light how stupid can one be. I’ve just been watching a youtube video only to discover it’s not the whole clutch which slides along the splines of the shaft as I thought, heaven knows where I got that idea from.

I wear varifocals so if anyone asks why I thought that I’m going to swear blind I was looking through the wrong part of the lenses smiley.

The one part of the clutch doesn’t move at all, it’s just the outer part that does all the moving in and out towards the driven pulley.

I’ve just run another check on the compressor with it off the car only to find clutch is not moving, when I connected some jumper leads from a battery onto the two pins of the plug it arched as though there was some kind of short, so I’ve done a resistance test with a multimeter and came up with a reading of 0.5 ohms.

I’m guessing that’s bad news because on a couple of American cars on youtube they are talking about the resistance should be between 3 to 5 ohms.

Maybe it would be cheaper just to simple ride around with windows open if itas too hot inside the car.

Nick Hughes02/07/2018 21:53:30
197 forum posts
129 photos

Replacement coils and clutch kits are available

Just had the compressor replaced on my astra and started looking at my options, just in case it was'nt covered under the warranty.


Edited By Nick Hughes on 02/07/2018 21:59:57

AJW02/07/2018 23:45:28
271 forum posts
117 photos
The coils are low resistance but could also have a diode across them and if connected the 'wrong' way round could well give you .5 ohm. I recently changed the coil on my Astra as it was 'open circuit' however once it was on the bench I discovered a thermal fuse fitted against the coil and it was this that caused malfunction - probably would have cost about 50p to fix if I had known earlier!


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