P38 Air Con Compressor clutch

OK - need some assistance here guys - the air con has stopped working...

Put the Faultmate on her, no faults on the HEVAC - the system has the air con swichted on - but the clutch is not engaging.

Tested the solenoid on the the compressor clutch and that works (hot wired it to a battery), so it is not getting power even though the HEVAC is thinking it is supplying it.

Have swapped around the relays, but that did not kick the clutch in, so assume it is not a relay problem.

Is there anywhere else I should check?

The actual HEVAC head units are known to fail. Look for dry solder joints if you are brave!

Datatek said:

The actual HEVAC head units are known to fail. Look for dry solder joints if you are brave!

Click to expand...

Hmm - could be, although when it is on the Faultmate, the HEVAC computer is saying it has turned the air con on - therefore I would have thought it shold be supplying power to a relay as the solenoid takes a fair bit of power.

I need to get the HEVAC panel out anyway as some of the bulbs have gone...

Yes, the logic may have turned the output on to activate the relay, but if there is a bad joint nothing will happen. Of course it could be the relay or your fuse box. Try substituting the relay for one of the same colour.

OK Data - next job then...

magictiny said:

OK Data - next job then...

Click to expand...

Bonne chance

I've got the same problem although I've not done the level of checking that you've done.

Someone else had this issue on rangerovers.net. Turned out to be a bad connection at the trinary switch connector...

Worth checking. I've not got round to it on mine...

Guy

Relay...wot relay?????
Thought the compressor clutch was triggered directly from the HEVAC unit ???
Main thing is to physically check that 12V is present at the two wires on the round connector attached to the aircon compressor when required.
If the 12V is not present,look further.
If you disconnect the round connector and apply an external 12V supply, the compressor clutch should engage, if not, either the thermal fuse has tripped (Link it out to confirm) or the clutch coil is faulty (Unlikely inmy experience).

Datatek said:

Yes, the logic may have turned the output on to activate the relay, but if there is a bad joint nothing will happen. Of course it could be the relay or your fuse box. Try substituting the relay for one of the same colour.

Click to expand...

Irishrover said:

Relay...wot relay?????
Thought the compressor clutch was triggered directly from the HEVAC unit ???
Main thing is to physically check that 12V is present at the two wires on the round connector attached to the aircon compressor when required.
If the 12V is not present,look further.
If you disconnect the round connector and apply an external 12V supply, the compressor clutch should engage, if not, either the thermal fuse has tripped (Link it out to confirm) or the clutch coil is faulty (Unlikely inmy experience).

Click to expand...

Ahh - I have already done that Irish - put 12v across the round connector and the clutch does engage - so not getting the Vs from where ever...
There are 3 relays in the fuse box with the aircon sign on them, 2 green and one yellow - so I assumed one has to do with the clutch...

It is no good - I am going to have to get the RAVE CD out and have a go at tracing the wiring to the clutch.

Ahhh sussed it out - no refridgerant, so just need to find out where the leak is - I have a sneaking suspicion that it is one of the valves as it is covered in yellow (or could br green) oil....

I assume the valves just unbolt from the pipework so are relativly easy to replace..

I've got exactly the same problem.........but I've had all the refridgerant properly removed. Had the system 'put to 4.5 torr?' and re-filled. Clutch still not engaging on the compressor.
Please excuse my ignorance......I'm used to fixing things with my 5lb 'tool fine adjustment' hammer......and this is well over my head. I dont even know what a HEVAC is.
Please help.
I'll buy you a pint

seanhath said:

I've got exactly the same problem.........but I've had all the refridgerant properly removed. Had the system 'put to 4.5 torr?' and re-filled. Clutch still not engaging on the compressor.
Please excuse my ignorance......I'm used to fixing things with my 5lb 'tool fine adjustment' hammer......and this is well over my head. I dont even know what a HEVAC is.
Please help.
I'll buy you a pint

Click to expand...

HEating, Ventilation & Air Conditioning

It is the name for the A/C system in the Range Rover....

:5bcheers2:

Thanks mate......I told you I know nothing

seanhath said:

I've got exactly the same problem.........but I've had all the refridgerant properly removed. Had the system 'put to 4.5 torr?' and re-filled. Clutch still not engaging on the compressor.
Please excuse my ignorance......I'm used to fixing things with my 5lb 'tool fine adjustment' hammer......and this is well over my head. I dont even know what a HEVAC is.
Please help.
I'll buy you a pint

Click to expand...

On early cars the aircon compressor clutch is operated directly from the HEVAC, later cars it's via a relay. If via a relay first place to look is at the relay in the under bonnet fuse box and also to check the box for signs/smells of burning.
It would be easier if you could get it on diagnostics.
If you put your location, there may be a member nearby with diagnostic kit.

Thanks for that

I'm in Bromley / South East London - but very willing to travel if anyone can help.

The 'plot' has gotten slightly more complicated......the heater blowers work ok - but now I dont get hot air.
No hot air and no cold air?

PLEASE HELP

The spring corrodes and breaks, so that it wont hold the clutch in. you can take the clutch apart, so that it is locked in the "on" position, other than that its a new Compressor .
Just had the same thing on a mates motor.

seanhath said:

Thanks for that

I'm in Bromley / South East London - but very willing to travel if anyone can help.

The 'plot' has gotten slightly more complicated......the heater blowers work ok - but now I dont get hot air.
No hot air and no cold air?

PLEASE HELP

Click to expand...

Do you get any air????

There are 3 Blend Motors in the HEVAC system, 2 for Air Temp control (L/H and R/H) and a third one for Air Distribution....(Face, Feet, Screen etc)

If you cant change Temp level, or the Distribution of air, sounds like the HEVAC has detected an issue with these and gone into fault....getting the codes read is a first port of call....then a Force Movement of the Belnd Motors using a Diagnostic Device would see if they are indeed moving....

They are little buggers and notorious for failing, trouble is they are a b*tch to get at. There are a number of shortcuts to the official 'Dash Out' procedure, so check out www.rangerovers.net as there are some good walkthroughs on there.

Get the codes read and see where you stand.

The blowers do work - and they HEVAC blower control works too.
I just get varying degrees of power - all at ambient air temp.
The HEVAC buttons all appear to work, windscreen, feet, face etc all work as they should.
Can anyone reccomend a good garage in South East London / North Kent or beyond?

The Mad Hat Man said:

The spring corrodes and breaks, so that it wont hold the clutch in. you can take the clutch apart, so that it is locked in the "on" position, other than that its a new Compressor .
Just had the same thing on a mates motor.

Click to expand...

Mad the diaphragm spring holds the clutch off untill it is pulled in by the electromagnetic coil to engage the compressor. The air gap between the clutch and freewheel is critical to good operation.

All I know was mates comp wasn't working and it was possible to make it be permanently on without the clutch presumably. When the compressor was replaced the spring was found in 4 pieces.