Aircon Compressor Not Switching On

Hi, the aircon compressor in my 1995 P38 4.6 HSE will not switch on:doh:. There is no power getting to the compressor. I have checked fuses 31 & 36 in the fuse box - both are ok. I noticed three relays in the fuse box relating to the aircon system. How can I test the relays Any other ideas what may be wrong any advice gratefully received......thanks.

It won't switch on unless there is gas pressure in the system. Also there is a thermal cut out on the compressor, if that's shot, the compressor will not run.
Get the gas pressure checked first.

Thanks Irishrover, I'll get it regassed and report back. The heating system in my P38 4.6 HSE is cold on each side when on HI setting. The distribution motor is directing the air as it should. I thought the blend motors were shot but I have been advised that it's unusual for cold air to come from both sides when set to HI (usually one side it hot while the other is cold etc.). A blocked matrix has been suggested. What do you think? Thanks again for your help, Kenny

PS I dont have any engine overheating issues - new engine fitted 9000 miles ago. My P38 has a newly installed LPG system.

One of the blend motors deals with the temp - whilst the other two (on the main box) deal with direction, I believe, so it could be the blend motor. I have a similar issue, one day it is pumping out freezing air, the next hot air (both blistiringly hot days...)

My blend motors are being replaced next week, whilst I am on holidays :cheer2:

Hi and thanks for the reply. My understanding is that one motors directs the air and there is a motor for each side to control the temperature - please correct me if I am wrong. Thanks, Kenny

it might be the heater water temperature sensor? only costs about £12, might be worth looking into that before the hefty expense of blend motors.

tommo138 said:

it might be the heater water temperature sensor? only costs about £12, might be worth looking into that before the hefty expense of blend motors.

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New one on me that. Did not know they had a heater water temp sensor. Where abouts is that situated?

wammers said:

New one on me that. Did not know they had a heater water temp sensor. Where abouts is that situated?

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its roughly behind the right hand side of the centre console behind the hevac, its in RAVE as ive been told ive got to change mine, im not 100% it has much to do with the aircon but pretty sure it does when its turned off and running the normal heater.
im prob totally wrong and someone with alot more wisedom about it will set me straight!!!!

ive found a pic of it, if it helps!

STC3256 SENSOR HEATER WATER TEMPERATURE | shop | www.lrseries.com | L. R. Series

You don't say if you have the Book symbol showing on the HEVAC.
Before jumping into it blindly and changing parts, I would get a diagnostic check done to pinpoint the fault(s).
I see you have a LPG conversion, loads of posts on here regarding air lock problems related to the LPG coolant pipework.
If both heater hoses are hot then there is every chance that the heater matrix is not blocked. In any event, a blocked heater matrix would make no difference to the operation of the aircon unless the temperature blend motor is shot or the blend flap sticking. Does the temperature rise and fall when changed on the HEVAC, irregardless of whether the aircon is on or off ?

Hi Irishrover,

I do have the Testbook symbol showing on the HEVAC.

Both heater hoses are hot.

Temperature never changes - best described as slightly warm/almost cold.

I'm taking it to V8 Kenny tomorrow to hopefully flush the matrix - then I hope to have some heat - I'll let you know how it goes.

I will have the aircon regassed a.s.a.p. and let you know.

Many thanks again for your help.

Kenny

Thanks also to tommo138

Hi, called Kwik-Fit today. They do a regas for £49 and if the system doesn't work after the regas they dont charge! Seems a good deal! I'll try to get it done next weekend and let you know how it goes. Thanks again, Kenny

kgeddes said:

Hi, called Kwik-Fit today. They do a regas for £49 and if the system doesn't work after the regas they dont charge! Seems a good deal! I'll try to get it done next weekend and let you know how it goes. Thanks again, Kenny

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I would read the other thread about Kwik-fit re-gassing first if i was you.

wammers said:

I would read the other thread about Kwik-fit re-gassing first if i was you.

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How do I find it? thanks....

Hi, I've read some stuff on here about the Testbook symbol - is it true that if the Testbook symbol shows immediately the engine is started the blend motor/s are faulty? Thank...

have heard alot lately about this deal kwik fit are doing, seriously sounds that they havent got a clue what they are doing when it comes to air con!!!!

No the Book symbol indicates that there are faults logged in the HEVAC system.It could be blend motors, sensor(s) or the Compressor Clutch coil is open circuit (Usually no gas).
The HEVAC does a self check every now and again, if, for instance the blend motors failed to do their full travel in a given time, it will store that fault. Doesn't neccesarily mean that the motor(s) are shot it could be that at that particular time they were a bit sluggish..maybe due to being cold. The motor(s) may also need calibrating as they have lost their open & closed position parameters.
Out of all the ECU's on the P38, the HEVAC is the most tempremental and throws a sickie for the least problem.