Strange HEVAC problem

Hello everyone!

My Range Rover P38 (GEMS 4.6 95') got a strange HEVAC problem. When engine running I cannot switch on front, rear and seat heaters, but when engine not running everything works fine.

With faultmate the only (current) error message:
Air condition request line fault

I had already checked the cable loom, but I cannot find any problem.

Has someone met with this strange problem?

Thank's!

Regard's:
Greg

Gergely Bakity said:

Hello everyone!
My Range Rover P38 (GEMS 4.6 95') got a strange HEVAC problem. When engine running I cannot switch on front, rear and seat heaters, but when engine not running everything works fine.

Click to expand...

Front = front demist?
Rear = Rear demist?
Seat heaters = seat heaters?

Hello!

Sorry:

Front heated screen
Rear heated screen
Left Right seat heaters

I've a vague memory of the GEMS being different to the diesel and Thor. I've got a feeling the GEMS has some input from the engine bay that the others don't and are held to ground on. I have no idea if that's your issue but if they work with engine not running that sort of ties in. Might be worth looking at differences between wiring on GEMS and Thor in RAVE?

Hopefully a guru will be along shortly with a better idea.

Today I double check the air con request line cabling and measure the GEMS input and output pin.

HEVAC should not power the front screen unless the engine is running.

The seats are switched by BECM, but managed by HEVAC.

Yesterday I found the problem.

The problem was a fault cable to becm (C114-15pin) which measure the alternator charge voltage.
Because of rust and corrosion sometimes the voltage signal drops to 7-8V.

That's why BECM instantly shut off heaters.

In this way another problem solved too, the rarely flickering battery lamp.

Regards:
Greg