T

TristanCarroll

New Member
Hi All,

Having probs with air con at the moment.

The Aircon pump isn't kicking in (the clutch isn't engaging)

I've checked the connector to the side of the pump, that seems fine. I've also checked and rechecked the fuses, they are all fine.

When I press the "A/C Off" button to turn A/C on or off I hear the revs of the engine change, but no action from the clutch on the pump.

It was working great and blowing cold, but then all of a sudden it stopped and I figured it needed regassing. But then when I looked under the bonnet I could see that the pump wasn't kicking in.

And there are no error lights indicating a fault.

I'm guessing that I need a new pump, but is there anything else I should should check before buying one??

Oh, I haven't checked the relays as I don't know what to check - can anyone tell me?

Thanks guys


Tris
 
The engine revs will change when you select aircon "On"-this is because a signal is sent to the engine ECU from the HEVAC and this in turn increases the engine speed to compensate for the extra load imposed by the compressor. The engine ECU does not know whether the clutch is engaged or not,- only that the compressor is called for.
The clutch on the compressor will not operate if there is not sufficient pressure (Gas) in the aircon system. First step is to get the system topped up and see if the charge holds. P38's are notorious for leaking Condensors (The Aircon "Radiator" with twin fans-located in front of the engine rad.). If the compressor and clutch work after this, then they are o.k.-But question is-where has the gas gone???;) ;) One pipe at the compressor should be hot and the other one freezing when the compressor is running with the clutch engaged.:D :D
 
They may vac. down the system first and sometimes, depending on how bad the leak is , it will show up on this. Get them to put some flourescent dye in with the oil charge during top up-if you have got a leak it should pinpoint the area under UV light in future.
The refigerant weight for a P38, 4.6 system should be around 1250 grams.They should vac out your system amd then regass with the above weight.:cool: :cool: :cool:
 
Might be best for you to go to kwik fit, i do believe if they cant gas your system they wont charge you for it, but check with them first
 
do your self a favour and with a screwdriver tap the clutch mechanism when it should be engaged, if it clunks into place (engine running) and starts to spin you need to up the voltage to the compressor magnetic clutch. no need to regas, or at least it wont be the lack of gas causing this fault.
there is a service bulitin concerning lack of voltage at clutch compiling of instructions to fit new loom, relay and fuse to aircon system, you need at least 11 volt at the clutch to operate it properly, i had 10.4v so fitted the loom and its been fine since. i also removed a shim from behind the clutch front plate, you want no more than 6/8thou gap, cant remember which but the smaller the better really. if you got rave cd you should be able to find the bulitin, the loom cost me just over £50 and it contained all the bits i needed. im cool so far...................
 
Just had another thought-If your compressor is a Sanden TRS 105 (Has square blue stick on label) which is fitted to the petrol models, there is a thermal switch fitted into the compressor body on the top at the end furthest away from the pulley and has two leads coming from it. This switch is in series with the clutch and cuts the compressor out in the event of comp. overtemperature. This switch could be faulty-simply link the two wires from this sensor together to check. If the clutch operates with the link in place, the switch is faulty.:D :D
 
Irishrover said:
Just had another thought-If your compressor is a Sanden TRS 105 (Has square blue stick on label) which is fitted to the petrol models, there is a thermal switch fitted into the compressor body on the top at the end furthest away from the pulley and has two leads coming from it. This switch is in series with the clutch and cuts the compressor out in the event of comp. overtemperature. This switch could be faulty-simply link the two wires from this sensor together to check. If the clutch operates with the link in place, the switch is faulty.:D :D
Click to expand...

i thought of this last last year when mine was playing up, i was hoping for an easy fix, i pushed the prongs of me multi metre through the insulation of the 2 wires just as they disapeared under pulley, easy test without linking, if you got a multi metre that is..........
 
Thank you lads for all your replies. :)

I tried the tapping method on the clutch, but no joy :(

Will check out that sensor option this evening.

But to be honest, I have a feeling it's the compressor itself. Although I can turn the clutch freely, there seems to be a tiny bit of resistance, as though the bearing have gone. Is this a common thing?

If I need a new one, what's the sort of price I'd be looking at? And are they easy to replace? - I was worried about the aircon gas hoses that attach to it - guessing it will let all the gas out and therefore need a re-gas after fitting the compressor?

Cheers

Tris
 
think the best thing to do to eliminate the compressor is to check the voltage going to the clutch, press the pointed probes of a multi metre through the insulation of the wires just as they disapear under the pulley to check voltage, if theres non then do the same but before the thermal cut out if theres non it aint the comressor, not the clutch part anyway. mine had a bit of resistancewhen trying to turn it, i guessed that ok as it does require the engine to idle faster.
 
You will feel resistance when you turn the shaft because of the pistons trying to compress. Usual problem (Apart from gas leaks etc.) is clutch failure, or thermal switch giving up the ghost. You can run with the switch looped out as the system is protected by two pressure switches. The system will need to be emptied before removing the hoses, then it's straightforward to change and get it regassed. Probably get a compressor on Egay for around £70-100, New will cost you £250+
As Redrange has advised, there was a wiring mod for some models which suffered from voltage drop at the coil but you need to get yours working in order to check the voltage and determine whether you need the mod or not. If you are getting a healthy 12V at the coil your o.k. as you are.
 
i actually have a spare coil for the aircon compressor clutch brought in error, so if yours is knackered theres one available, you wil prob find it ok as it extremely rare for these to pack up.
 
If there is a fault on the HEVAC which it can't clear itself-such as an output down, the "Book" symbol will come on. The HEVAC goes through a check & clear psocedure every time it's powered up (Ignition turned on).
 
Not checked anything yet lads.

Just got back from a long weekend in me Caravan at Ledbury.

Will be checking everything I can out in the week now.

Cheers,

Tris
 
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