My daughter has the P38 250 miles away at school. She called today because as she was driving on the highway the ABS, TC, Brake and SRS lights came on and then the AC shut off
and the lights to the HVAC unit all turned off.

When she was able to stop, she turned off and restarted the RR. Again ABS, TC, Brake, and SRS lights came on. The AC came on then shut off as did all the HVAC display lights.

At least it's all consistent. Should I be looking at relays or fuses? I'll be relaying any info from here to her via the phone/F@ceTime. She's not afraid to get her hands dirty but has limited experience with this Land Rover.

The SRS might be unrelated as it was turning on and off prior to me dropping off the P38 a month ago. I thought I had fixed it, but perhaps not.

Thanks in advance.

what year and engine is your p38 ?
and where are you based someone on here might be near to her and could do diagnostic tests
the srs light could be loose wire under the seat
some times the lights come on when battery voltage is low
or could be faulty abs sensor

bad fuse box perhaps?

Seems like a lot of unrelated circuits losing power at the same time?

karlos01 wrote:

what year and engine is your p38 ?
and where are you based someone on here might be near to her and could do diagnostic tests

the srs light could be loose wire under the seat

some times the lights come on when battery voltage is low

or could be faulty abs sensor

it's a 2000 with the Bosch engine management.
she's in Oklahoma. we have a good indie Land Rover mechanic there. but i was hoping there might be a simple fix to save the trip to him.

Aragorn wrote:

bad fuse box perhaps?

Seems like a lot of unrelated circuits losing power at the same time?

this was my thought, as well. the losses do all seem unrelated.

With all of those seemingly unrelated things going on, a possible common cause would be a bad ground.
There is one under the climate control, and if I recall, another under the dash on drivers side.
All grounds on a P-38 MUST be clean and tight. Just giving them a wiggle is not enough. Remove, wire brush
re tighten. A bad ground causes current to flow from one circuit to another rather than to the proper return path.
Probably more likely to be the one under HVAC.
Fuse board is another suspect. Can she remove the cover and have a sniff for the smell of burnt electrics?
My bet is on bad ground though. Have a look at RAVE which will show you what circuits share the ground points.
I am away from my computer that runs RAVE, but Gilbert has them memorized! I am sure he will chime in when he wakes up.

Not memorized, I just keep it open so I can quickly look stuff up. Ignition switched power to the HEVAC comes from a connector on the back of the BeCM that can be accessed by lifting the carpet in the RH rear passenger footwell (it's the only connector on the back so not difficult to find). That connector can overheat and lose power. On a pre-99 car that same feed also goes to the radio and the brake light switch and I was wondering if a loss of power to the brake light switch would cause an ABS error but it appears that on a 2000 they don't use the same feed (so that is that theory out of the window....). But, there is a feed from the ABS system to the HEVAC (no idea why) so it is possible that an ABS fault could shut down the HEVAC.

Not enough juice on the battery...I only saw the vanishing hevac once and that was the battery collapsing... Is the alternator charging properly? Have you uprated the VR?

romanrob wrote:

Not enough juice on the battery...I only saw the vanishing hevac once and that was the battery collapsing... Is the alternator charging properly? Have you uprated the VR?

My only experience with a weak battery gave the gearbox error and the, I think, if memory serves me well, the transmission went into limp mode. New battery fixed those issues.

I'll definitely have the battery checked, though.

Gilbertd wrote:

Not memorized, I just keep it open so I can quickly look stuff up. Ignition switched power to the HEVAC comes from a connector on the back of the BeCM that can be accessed by lifting the carpet in the RH rear passenger footwell (it's the only connector on the back so not difficult to find). That connector can overheat and lose power. On a pre-99 car that same feed also goes to the radio and the brake light switch and I was wondering if a loss of power to the brake light switch would cause an ABS error but it appears that on a 2000 they don't use the same feed (so that is that theory out of the window....). But, there is a feed from the ABS system to the HEVAC (no idea why) so it is possible that an ABS fault could shut down the HEVAC.

Thanks. I'll see if she can check the connector.

You'll get the Gearbox Fault message if the battery is getting tired and the voltage drops when cranking. If the battery is dying while driving, things will shut down in order of priority, so things like the AC and radio will stop working first. I had a bad connection between the alternator and battery so although the alternator was still working (so no warning messages) the power wasn't getting to the battery. It was some years ago (and Rob's suggestion reminded me of it) but first the EAS didn't rise, then radio went off, then HEVAC then ABS, then gearbox fault before there was finally not enough juice left to run the engine and it stopped. By then I was about 100 yards from home and managed to coast the rest of the way.....

Talked to my daughter the other day and she said the ABS lights are all turned off and the AC is working again, though occasionally blows hot air. She has not had a chance to check on the connector(nursing school graduation coming up).

I really hate intermittent electrical issues, especially when the RR is 300 miles away. We have a trusted indie Land Rover mechanic where she is, so I think I'm going to have it dropped off there. He has several P38s sitting in the yard, so I may see if he can swap in a HVAC control face with a working LCD screen while he's working on the other issues.

I'd just have the indie test the alternator, and if necessary ship him a volrage regulator that he can change over...before you start messing around with the hvac. Iwd also highly recommend installing a voltmeter/USB socket in place of the cigar lighter, then your daughter can keep an eye on the battery voltage

Last week the RR decided not to start at all. Per my daughter, starter did nothing just one tick when she turned the key. So, she replaced the battery
and all seems good now. I did ask her to have the alternator tested so we can confirm nothing is wrong there.

Thanks to all who responded and gave helpful direction.

New battery fixed the issues until it, too, ran dry. My daughter called to let me know that the AC quite working, the dash lights came on, TC stopped working, etc. as my wife and I were half way between St. Louis and Tulsa.

I was able to confirm that the alternator had failed, or more specifically, the voltage regulator. The code reader gave a reading between 17 and 18 volts at all times. I managed to track down the only P38 alternator in town(because, of course, i'd left the spare in the basement) and install it Saturday morning, three hours before my daughter's graduation. Both alternator and battery tested good and we were able to make the 400 mile drive back home with no issues.

Great, and congrats to your daughter.

all is well when it ends well !