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Discussion Starter #1
Aloha,
Been working the few kinks out of the new Borrego, and wanted to share an interesting observation.
In troubleshooting the Air Con, I eventually discovered that the controller the guy I bought it from had put in was from a very early truck, probably an 96 or 97.
He had the Left fan going at full speed, so assumed it was the controller, and on advice of a "Good RR factory tech" he got a different controller. Same problem, and no display. Third controller was another oldie, but had a nice display.
Knowing about the transistors shorting issue causing full speed operation, I grabbed a blower from the wreckers when I went there to find a jack, and a few other odds and ends.
Changed the trinary switch as I got a spare for free. Compressor would not kick in. Fully gassed.
The Nano showed codes for Shorted Windscreen Pos, Shorted RH blend Motor Pos. Two fan related faults as well.
Changed the blower, and speed control is good, took the good display board and the 2001 control board and made one good unit that will drive the relay.
The early HVAC controller will fault out as there is not enough resistance on a relay when it wants to see a clutch coil.
Once the new controller was in, I cleared all codes, and the Checkbook and ! went away!!
AC still would not activate Clutch, so I looked at the readings for inputs to the HVAC and saw the Ambient air at -40c on a +25c deg day......I believe If you unplug it it will default to -40. Fiddled with the plug on the sensor, and it started playing nicely. Compressor cycles, and all is good.
So, it seems one shorted to high speed motor can cause the HVAC unit to throw several false codes!
Moral of the story?:
Always check the part numbers to be sure the unit you are putting in is compatible.
I used search and found a handy chart of all the controller part numbers that Marty posted a few years ago that told me immediately exactly what was wrong:dance: Thanks, Marty!
 

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LEGACY VENDOR
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4,159 Posts
Good to hear the information is still being useful for people!

Half the problem is with the sellers of second hand parts (at least here in the UK) - if it looks the same then most of the time it's listed as "Range Rover P38, 94-02" whether the part will actually work in the whole range of vehicles, or not - especially in the case of HEVACs..

If you ever end up with dead pixels, then check out my HEVAC pixel fix - replaces the ribbon connector which peels off over time..

Wish I had the space and time for another P38 for myself... I'm slowly making a bit of progress on the first of my restoration project p38's - but they're being done with the aim of selling on!
 

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1,418 Posts
Discussion Starter #3
Aloha,
I now have a working old style controller with a burnt out backlight and a whole bunch of pixels out.
I was looking forward to trying out your fix, now I have a test subject. Anyone need anold style HVAC controller?
 
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