Aircon woes

[adm333]

The latest feature sent to test my love for this vehicle, is airconditioning that stops working when it gets hot.

When I set off in the morning it appears to be working 100%, very cold air, comfortable no problem. As everything heats up it stops blowing cold air and essentially it is just blowing air.

It appears that the compressor stops cutting in.

I saw in RAVE that there is some kind of a thermal cut out switch on the compressor, but not sure if that could be the problem or the main controller not working properly.

Has anyone had this kind of problem before ?

[Scouse]

Have you checked that it is the clutch not staying enagaged?

If that's the case:
1. How's the compressor clutch air gap? That seems to be the common cause of the clutch dropping out when hot.
2. Does your RR have the extra clutch relay fitted?

[adm333]

Hi Scouse

Please tell me more about the compressor clutch air gap as I haven't heard of it before.

How would I check for the additional relay ?

Signed
Clueless !

[Scouse]

Please tell me more about the compressor clutch air gap as I haven't heard of it before.

Have a read here under "Compressor Clutch Failure":
Range Rover P38/4.0/4.6 Common Problems and Fixes (http://www.rangerovers.net/newrremedies.htm#airconditioning)

Basically the clutch wears & the gap grows. The magnet isn't strong enough to bridge the bigger gap so the clutch drops out.

Chances are that the shim has been removed already but it's only a 30sec job to check. If it has been removed & the gap is still too big, then you can machine (or grind as I did) the centre boss down.

LR have a mod to the harness too to make sure that voltage drop isn't the cause. It's not exactly cheap but it does help.

[Scouse]

More info on the air gap here too (with piccies):
http://www.rangerovers.net/forum/7-range-rover-p38a/32567-removing-ac-pulley.html

[adm333]

Cheers Scouse

I take it you can see it all once you remove this black metal cover ?

Do you have to remove the drive belts or anything major ?

[adm333]

Scouse

OK, I think I might have the extra wiring loom and relay.

However, can you confirm which relay should be used.

On my fuse box it has a green outline for relay 10 indicating it should be one of the green realys, but in fact there is a yellow one in there.

I have a spare green one, but I thought I would check to see which one is correct first.

Cheers
Dave

[adm333]

Alright, I found the technical bulletin on my RAVE CD and can confirm that I have the additional wiring loom modification.

However, I notice 2 points that may be rendering it inoperable.

1. It states that a 10 amp fuse should be in slot F40 in the engine bay fuse box - there is none there now.

2. Studying the circuit diagram for the relay shows a 5 point relay, which is a green one. I seem to have a 4 point yellow relay.

So I figure if I fix those two things I might be closer to a cooler ride.

Alternatively, look for a big smoke cloud on the horizon above Carina ....

Signed
Clueless, now dangerously armed with partial information

[Scouse]

Our P38a isn't here ATM but I'm sure the belt doesn't need to come off. The nut secures to front clutch plate to the shaft so as long as it undoes OK, the plate should come off easily. If the nut is very tight, then you'll have to lock the plate to stop it turning somehow (I wouldn't recommend big multigrips but they worked for me).

The car is back tonight so I can have a look which relay & fuse goes where but I'm sure Ron will have the info today..........won't you Ron....:)

[p38arover]

Did the later cars use a different fuse box?

The new relay (in mine) went into the vacant RL10 slot and is black. :D

It's a 4-pin relay so a yellow will be fine - the other pin is not connected (see diagram below). F40 has a 10 amp fuse.

https://www.aulro.com/afvb/images/imported/2011/11/660.jpg

[Davehoos]

the front plate has shims to set the air gap.
remove to reset it about 0.5mm+

then test to see if it drags when hot.

problems:
compressor gets old the imput shaft can be pulled in reducing the gap when low pressure is pressent in the suction side of compressor-[cold].so it drags.afte adjusting run withot the cover to test.

Low voltage-i think some have a water overheat relay-most at sometime get an extra relay fitted with direct fused power.some had pressure switch isues-no reason full power must go through these switches.

the thermol overload in the rear dies-it a mechanical switch to brake the circuit when the compressor overheats.
if the clutch has been slipping often the coil needs extra current [evidence of a short].

clutch is common with another car-compressor is not common.replacment compressors are often not the same.

P/s often have to take the high spots of the surface to stop it slipping.the pulley/disc have recessed cooling slots and the high spots cut into the slots breaking the pulley.

[Blknight.aus]

Im up for a play with it, If I can find the right chuck head for my lathe.

[adm333]

I'll have a go at removing the shims, and if that doesn't work I'll look at more drastic measures.

I took it out for a drive and it seemed to go a lot longer, so I think the power side has helped, but now it must be clutch itself I'd say.

I saw a yellow billboard saying "Want Longer Lasting Aircon ? "

I might give them a call
:D

[adm333]

Can anyone recall is it is a right hand or left hand thread to remove the clutch nut ?

[p38arover]

Can anyone recall is it is a right hand or left hand thread to remove the clutch nut ?

Look at the direction that the belt turns over the aircon pulley. Undo the nut in that direction.

[adm333]

I have managed to get the clutch off. I'm not sure if the copper looking washer in the first picture is the "shim", not having met a shim before.

If so, it seems to be spinning around on a thread or something, it wont just pop off the shaft.

Ron, when it comes to machining did you machine around the contact (red arrow) or the shaft (green arrow) in second picture ?

[Scouse]

Ron, when it comes to machining did you machine around the contact (red arrow) or the shaft (green arrow) in second picture ?Green !!

[p38arover]

Green !!

Green!

The thing you can see on the shaft is probably the shim - a thin washer.

[adm333]

I could not get that washer / ring off, I'm not convinced it is the shim.

It certainly wouldn't prize (sp??) off and I didn't want to force it.

It seems more like the inner ring of the bearing. There is a corresponding outer ring and rubber /plastic texture in between.

[Davehoos]

I think he's refer to the inner part of the nose bearing.

the rotor/armature--look about half way out and you see a ridge.this high point can stop the plate getting grip on the shiny chrome looking bits.

[adm333]

I think he's refer to the inner part of the nose bearing.

the rotor/armature--look about half way out and you see a ridge.this high point can stop the plate getting grip on the shiny chrome looking bits.

Yes, I guess I was asking if its worth trying to smooth out that ridge at all.

[Davehoos]

i often put the hub in the lathe when replacing the bearing.

the hub will have hot spots so it hard to machine.most of the time they are out of square.

ive had problems with these slipping when ive made one up-miss matched patterns- from two compressors.they often dont bed in.

you often see this in hot weather when the compressor starts with a high head pressure.

im not going to say ive hit these with the grinder when spinning as that would be dangerous.:)

[Davehoos]

P/S its not that bad.