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Discussion Starter #1
Long time reader first time posting though.
Problem, the hvac display is completely dead. No screen, no lights on various buttons when pushed, no fan, nothing, void of all life!
Previous work done on system and rig,
Opened up fuse box, inspected and all was found to be in good condition, nothing burnt or cracked etc.. Have sent the hvac head unit out for reconditioning (new ribbon cable & bulbs, etc). Rebuilt my blower motors as per several topics here..
Here is what happened. The car sat idle for aprox 9 months due to working out of town. Charged the battery and started right up. Blowers were both on for a few seconds. Then all went dead. Have cleaned grounds, checked all fuses,relays,& connections. Im stumped.... Please help, i dont have rave.
 

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What year rig? Head units, fuse boxes wiring etc are different.

RAVE is free to download.

Sounds like possible rodent damage to the ignition side of the control panel.
 

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Do the lights on the EAS display come on? They share the same ignition switched feed as the HEVAC (as do the stop lights) so if they aren't working either it is likely it isn't getting any power. Power comes from the White wire on pin 9 of C258 at the BeCM. This is the only one on the back of the BeCM and accessible from the rear footwell and can burn out the contacts.
 

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1970-1995 Range Rover Classic
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455 Posts
please check all connectors behind the Hevac. <br>
Check C101/201 <br> on the RH of passengers feet or driver's if you have a RHD
Check ALL BECM fuses <br>
Check C255 and C258 on the BECM <br>
in case this is chinese to you study the BECM and Hevac section in the repairs here on this site till you know it by heart :)
 

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No brake lights. No power on pin 9.
Dry joint on the power board of the BeCM where the pin for the socket is soldered to the PCB. Two choices for repair, either pull the power board and re-solder the joint or, the quick and dirty repair, run a piece of wire to the White wire from the load side (the side that isn't live with the ignition on) of Fuse 17. That will simply bypass the route through the BeCM from Fuse 17 to the wire that needs it.
 

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Had the same fault on 3 different cars, the load on the pin causes it to overheat so the plug/socket gets too hot which in turn causes the soldered joint to crack. Running the external jumper wire is easy, quick and gets the brake lights working again which is a bit more serious than the HEVAC (but not always noticed by the driver). Glad to have been able to help.
 

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1995-2002 Range Rover P38A
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"run a piece of wire to the White wire from the load side (the side that isn't live with the ignition on) of Fuse 17."

Great "field expedient" repair! Thanks!
Just for future reference, a minor clarification.....Both sides of a good fuse will have the same voltage on them.
Are you saying the fix is to jump (a switched positive) to pin 9 from fuse 17? so, pull fuse 17, switch on ignition, find load side of fuse (no power), attach jumper there, put fuse back?
(And, I will assume the white wire is the one attached to pin 9?)
Cheers!
 

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"run a piece of wire to the White wire from the load side (the side that isn't live with the ignition on) of Fuse 17."

Great "field expedient" repair! Thanks!
Just for future reference, a minor clarification.....Both sides of a good fuse will have the same voltage on them.
Are you saying the fix is to jump (a switched positive) to pin 9 from fuse 17? so, pull fuse 17, switch on ignition, find load side of fuse (no power), attach jumper there, put fuse back?
(And, I will assume the white wire is the one attached to pin 9?)
Cheers!
That's right Bolt. Pull fuse 17, check which side isn't live with the ignition on, poke a wire in the hole and then push the fuse back in. Run that wire around to the back of the BeCM and Tee it into the White wire that is connected to Pin 9 of C258. All it's doing is bypassing the PCB track in the BeCM from the fuse to the socket and the location of the dry joint so even the fuse blown warning will still work. If the wire is run behind the seat trim it can't even be seen so everything looks and works as normal. First time I encountered this fault the HEVAC display would go off every time the brakes were applied as the iffy connection at the BeCM could supply enough power for the HEVAC but went high resistance when the brake lights were switched on.
 

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1995-2002 Range Rover P38A
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1,422 Posts
Well, to dig this thread up and go with it a bit........
I am here in Hawaii getting the white 02 ready for a cruise to California, and have a sudden case of intermittent HVAC.
Bit odd in that it started randomly coming on and off at first, then within a few minutes, it stayed off.
The screen comes on for a second when you turn on the key, then off until you crank, and engine starts when it comes on for another second.
On the first occurrence, it was indeed going off when brake was pressed, but only a couple of times. after those, it stopped completely.
I have swapped Becms for my spare with same result. Seems no point in doing the pin 9 trick?
Brake lights are fine as well. All fuses and relays look good, and fuse box is a new replacement about 20k miles ago. Plug on the back of Becm looks ok.
It has randomly flickered back on while driving.......
I have pulled unit and checked all plugs on back. all good. (I Failed to double check earth point beneath Hvac unit....oops....)
Screen back light is coming on, just no data display, and nano cannot talk to it.
I will check behind kick panel in the morning.
Anything I am missing here?
Where is the switched B+ coming from? Becm?
Cheers!
 

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99 onwards are different so the fuse 17 trick won't work. Power to the HEVAC comes from fuses 35 (ignition switched) and 42 (permanent live) in the engine compartment fusebox, along with fuse 8 via relay 7 in the BeCM fed from pin 6 of C1276 on a White/Pink wire. C1276 is the same one on the rear of the BeCM that was called C258 on earlier cars.
 

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1995-2002 Range Rover P38A
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Thanks Richard!
I have a meter here, but no copy of Rave.......
now, at least i can find out where the power is not happening from.
Looking like it is under bonnet as both BECMs do the same thing.......
Cheers!
 

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Tut, tut, I've got RAVE on a USB stick on my keyring so no matter where I am, as long as I have a computer, it's always with me.
 
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