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[05omegav6]

Got the aircon regassed, but the compressor clutch isn't engaging...

0v going to the compressor, so where to be looking for the culprit

[05omegav6]

Clutch engages when connected direct to battery, aircon working as expected, which is a start

Fuses 12, 14 and 15 ok as well have swapped the relay with both the horn one and K87. No change, all three relays work on the horn circuit, so confident that I have ruled out that problem.

Every thing else (according to the book of blocks) seems to point to the engine ecu or wiring to the relay

[05omegav6]

Might be a coincidence, but the coolant pump on the radiator has just gone up in smoke

When compressor connected direct to battery...

1. Front fans run constantly.
2. Second stage fan in the cabin air intake runs.
3. Main fan cuts in/out as expected from the gauge.

Plug compressor relay in, and 1. and 2. both cut out instantly, 3. stays the same.

What is likely to happen with the clutch permanently engaged, even when engine off?

[Andy B]

... or wiring to the relay

At some point before I owned the car, the wiring underneath my battery had been 'modified' by Vauxhall. I've the receipt for it somewhere.
Any use?     

[05omegav6]

All looks to be in order under there

That looks like I soldered it

Front fans do come on with the compressor off, but only after the rear fan which I believe is normal when aircon off...

[RobG]

Got the aircon regassed, but the compressor clutch isn't engaging...

0v going to the compressor, so where to be looking for the culprit

Faulty low pressure switch

[05omegav6]

Got the aircon regassed, but the compressor clutch isn't engaging...

0v going to the compressor, so where to be looking for the culprit

Faulty low pressure switch

Presumably there are only three things which will tell the ecu not to power the clutch relay...

1. Low pressure.
2. ECO switch on the climate panel.
3. OFF switch on the climate panel.

How reliable are the pressure switches, and are they available separately 

[RobG]

Got the aircon regassed, but the compressor clutch isn't engaging...

0v going to the compressor, so where to be looking for the culprit

Faulty low pressure switch

Presumably there are only three things which will tell the ecu not to power the clutch relay...

1. Low pressure.
2. ECO switch on the climate panel.
3. OFF switch on the climate panel.

How reliable are the pressure switches, and are they available separately 

How long`s a piece of string. Can be obtained separately

[05omegav6]

All the other wiring seems to be behaving as expected. When the clutch is plugged to the battery, the front fans run instantly, and I have disconnected the radiator pump as that's now dead.

Shall try the pressure switch next

Thanks all

[biggriffin]

low pressure switches are available but cost £58.+ on tc, hence i got a s/hand one from scrappie £2.00.

[05omegav6]

 

Presumably the system will need regassing again

[RobG]

Presumably the system will need regassing again

Depends how quick you are with a spanner

[05omegav6]

 
Might only make a small hole in the Ozone layer if I remember to unplug it first

[Andy B]

Might only make a small hole in the Ozone layer if I remember to unplug it first

If the a/c specialist is going to re-gas your system afterwards, they'll normally de-gas it for you for free.

[05omegav6]

I try to keep things simple... the machine is much quicker if there's nothing to drain out of it

A valid observation though