P38 Air Con Clutch Not Engaging

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If it works when the relay is forcibly made by hand then it has to be the coil side of the relay has insufficient volts to it, or an HR earth limiting the current through the coil.
As the OP says he can only see 4v on the terminal it has to be the wiring to the relay coil surely?
 
DanClarke said:
If it works when the relay is forcibly made by hand then it has to be the coil side of the relay has insufficient volts to it, or an HR earth limiting the current through the coil.
As the OP says he can only see 4v on the terminal it has to be the wiring to the relay coil surely?
Click to expand...

One would think so.
 
wammers said:
Which ever Hevac is used, it still outputs 12 volts from pin 7 to C0792 connector later models or C244 early models. Which is the same connector with changed definition. Early one pulls the compressor later one pulls the relay. Both give same effect. However do as Keith says and check Hevac part number yours should have latest number. Latest will work on all cars but some early ones will not work on later cars.
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The early HEVAC expects a minimum load from the clutch coil, the relay coil does not provide sufficient load so the HEVAC does not switch.
 
Datatek said:
The early HEVAC expects a minimum load from the clutch coil, the relay coil does not provide sufficient load so the HEVAC does not switch.
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OK that explains that then. As said latest Hevac will work on all early cars but some early Hevacs will not work on later cars.
 
Don't forget to read the Hevac diagnostics, would be the first thing to do. In outputs, try to send the order to AC . If that doesn't work , check the cables. I have seen so many idiots connecting radios to Hevac cables for feed.
 
Radar1946 said:
The 4v is coming from the relay socket terminal 86.in the fuse box.
I will get the hevac out and check.
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The 4 volts may be a phantom voltage, if you apply a load like a 5watt lamp to earth, odds on it will disappear.
According to my copy of RAVE, the relay has only 4 pins rather than the more normal 5 and there is no mention of 86, pin 6 is listed as from the HEVAC, pin 2 is ground, Pin 5 goes to the 2 state switch and from there the clutch and an unnumbered pin is 12 volts. You know the last 2 are OK as if you manually close the relay the clutch engages, so you are left with the HEVAC line or the ground that need looking at. If you pull the HEVAC out, you should be able to identify the socket pin that goes to the relay, if you apply (carefully) 12 volts to that pin, the relay should energise which will prove the wire and the fuse box. That will just leave the HEVAC. If it's the early version, there is a mod to make it work with the relay either by leaving the relay out and jumpering pin 5 & 6 or adding a resistance to increase the load. I'll have a look and see if I can find details.

UPDATE, I cannot find the mod details, it's on LZ somehwere. The wire to the relay is from pin 7 of the white connector in the HEVAC C0792
 
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I have taken out the HEVAC out and it is from a 98 with exc written on the case, So someone has changed it in the past. I have found a 2001 Hevac, due Friday or Saturday.
I had done all this before I read about the advice about the pins. I will put the new HEVAC in and see if that cures it. If not I will try all the options you have given me, it is all very much appreciated.:)
 
Received the Hevac Saturday, opened the box and the Hevac was another early one, and not the 2001 advertised. I thought I will try it anyway but no good.
I am sending this one back and he is giving me a refund. I have now ordered a 2001 as they said it was definitely a 2001, and the one in the photo which shows the model number etc.
Now got to wait until Thursday, I will try all the info given to me while I wait..
 
Radar1946 said:
Received the Hevac Saturday, opened the box and the Hevac was another early one, and not the 2001 advertised. I thought I will try it anyway but no good.
I am sending this one back and he is giving me a refund. I have now ordered a 2001 as they said it was definitely a 2001, and the one in the photo which shows the model number etc.
Now got to wait until Thursday, I will try all the info given to me while I wait..
Click to expand...

I've had a bad experience with people not sending what was advertised and just sending any old p38 part claiming it would fit. Even worse they argue the toss afterwards. Classic Rides North Wales or similar is one seller I won't use again.
 
Radar1946 said:
Received the Hevac Saturday, opened the box and the Hevac was another early one, and not the 2001 advertised. I thought I will try it anyway but no good.
I am sending this one back and he is giving me a refund. I have now ordered a 2001 as they said it was definitely a 2001, and the one in the photo which shows the model number etc.
Now got to wait until Thursday, I will try all the info given to me while I wait..
Click to expand...

You need JFC102540 less heated seats or JFC102550 with heated seats.
 
I checked the wire coming from the hevac plug to the fuse box, to see if it was broken or damaged.
I connected a meter wire to the plug that fits in the rear of the hevac and the other end to the terminal in the fuse box,
the wire had no problems, so I connected 12volts to the hevac plug and sure enough 12volts was coming into the fuse box.
As you have said it must be the hevac. Roll on Friday.
 
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