P38 Air con Problems

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peter040

New Member
Posts
23
Location
United Arab Emirates
Hi Guys
I have a 1998 P38 and been having air con problems. I live in the Middle east Dubai. The problems started with the Blend and distribution servos not working so I started by replacing them but the new ones did not work, it was then put on test book and I was advised that the ATC ECU was not working. I have replaced the ATC ECU, replaced the 3 servo's blend and distribution and still it does not operate the servos it has been put on test book all faults cleared and reset. still doesnt work the servo's and the A/C

Can any one help

Peter
 
peter040 said:
Hi Guys
I have a 1998 P38 and been having air con problems. I live in the Middle east Dubai. The problems started with the Blend and distribution servos not working so I started by replacing them but the new ones did not work, it was then put on test book and I was advised that the ATC ECU was not working. I have replaced the ATC ECU, replaced the 3 servo's blend and distribution and still it does not operate the servos it has been put on test book all faults cleared and reset. still doesnt work the servo's and the A/C

Can any one help

Peter
Click to expand...


Have you looked here:


Range Rover P38/4.0/4.6 Common Problems and Fixes


hth

zzr1200
 
Hi, im also havin probs with my aircon, when the say about the 'ETM' onr rangervoers.net what are they talking about there as i could do with a copy?
 
thanks I dont think the A/C compresser or the clutch is the real problem as this was all working ok with the old ATC ECU the problem has only started when the servos and the ECU has been changed it has been restarted with test book but still no luck. It has had a new fuse box fitted and I have checked and re-checked all the conections.
 
Check that the compressor is getting a signal to turn on,if it is and compressor still isnt working remove washer behind clutch to close air gap up.
 
I have now fitted the distribiton and blend servo's and rebuilt the recirculation servo's and now seam to be working ok. I have read a little more on the system and the distribtion and blend servo's have a feedback potentiometer which i think has to be under presure/resistance. I think the reason they were not working was I was trying to get them to work with them just conected to the ECU and not conected to the flaps. Oh well you live and learn. How ever the A/C is still not coming on DOES this have to be initialised by test book?????
 
Yes-the motors have to be calibrated using Test Book,Rovacom or Autologic. This "Teaches" the flap open & close positions. The potentiometers send a variable voltage signal back to the HEVAC which is translated as a position to put it simply, this is why the HEVAC needs to know the open & closed position so that the motors cannot be over travelled which will put unnecessary strain on the flimsy plastic gearing inside them.
 
Yer thanks Irishrover thought as much I no how the A/C should come on and off but for some reason its not coming on at all May this has to be reset by test book as I have fitted a new ATC ECU
 
Yes the HEVAC has to be taught with regard to the motors but the aircon should work irregardless. Are you sure there is sufficient gas in the system? or you could have a faulty pressure switch which is telling the HEVAC that there is no gas, in which case, the compressor will not cut in.
 
Is the book showing on the screen??

What happens if you start the vehicle, make sure the A/C is off, set it to LO both sides with the air to the face vent, turn up the blowers to half and then press the button to let the A/C come back on, do you get any sort of drop in engine revs at all like the engine ECU is going to compensate for the additional load that the compressor running causes??

When the A/C is on and both sides set to LO are you getting ANY voltage at the connection to the compressor?? Check with a multi meter.

What year is the P38?? Do you know whether the washer that can be removed to close up the clutch distance on the compressor has ever been removed??

Do you have the Electronic Troubleshooting Manual (ETM) found in RAVE??

-Wills :)
 
Hi Wills thanks
I will check it in that order but have check it all sorts of ways. I do have the Rave CD but I do have diffculty in understanding the wiring diagrams. As i have said I live in Dubai so all sorts of things could of happend to to car before I got it with the very high level of technician that we have here (not). It is a 1998 very basic car.

I shall check the clutch and let you no today.
Yes the book is showing on the screen.
Yes I do get the drop in engine reves.

Many thanks
Peter
 
Hi
I have put it all back together and the servo's are all working ok the A/C still not coming on Have taken the washer out of the clutch Made no difference,there is no power to the clutch, I conected it straight to the battery and the compresser comes on I checked the voltage at the dual switch and there is power there, So not sure what to check next. May be as i have fitted a new ECU it will needs to be reset by testbook althought I cant find any were that says this has to be done.
 
The aircon function in the HEVAC cannot be "Reset" or initialised by Test Book etc. The only thing the diagnostics will do is to "Teach" the HEVAC the blend motor calibration and check feedback from sensors etc. As stated previously, the compressor will not be energised via the HEVAC if pressure switches and other input signals are not present.
 
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