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Main beam turns on switched live!

Posted: 02 Sep 2024, 19:07
by saysomestuff
So I've just discovered something very odd.

With the ignition off on my 1990 T3 doka (ADY 2l 8v engine) if you turn the lights on and pull the main beam stalk, the stereo/usb/wipers work!

I've had it for a few years and never noticed this. I recently removed an old alarm but it was only piggy-backed into stuff and I didn't notice this issue at the time (and have never really had cause to notice it before tbh).

There is an after market light bar that comes on at full beam which was on the van when I got it, feeling like that may be the issue.

Key can be completely out and it still does the same. Any ideas folks?

Re: Main beam turns on switched live!

Posted: 02 Sep 2024, 19:08
by saysomestuff
Oh worth noting it doesn't prime the fuel pump, that only happens properly on the key.

Re: Main beam turns on switched live!

Posted: 02 Sep 2024, 19:30
by Robsey
Yes, it is a known issue with the high-beam stalk setting.

It bypasses the X relief relay, supplying current to all consumers on the X rail.
All the big heavy users like the blower motor, front and rear screen wipers, rear window demister element.

As for the fuel pump, no it is not powered by the X rail.
Otherwise the power to the fuel pump would be cut during cranking.
Precisely the time you need the fuel pump to be running.
The fuel pump is on the "15" ignition live rail.

X is only live with ignition on, but not during cranking.

Re: Main beam turns on switched live!

Posted: 02 Sep 2024, 19:32
by saysomestuff
Ha ha wow, what an interesting quirk.

Thank goodness I haven't messed something up!

Thanks so much for setting my mind at ease.