Headlamp retract problem - help please!

[Peter Gidden]

Right, i've been on this all day without success. I'm more than happy getting stuck into electrical problems, but this one is so far, defeating me.

Car: Imran's AW11 SC (no Headlamp Retainer Relay ever fitted)

Problem: Headlamps won't lift or retract.

Essentially, the signal from either the flash stalk or light switch to the Retractor Relay results in an earth on pin 8 (stalk) or pin 6 (switch).

This results in a positive output on pins 1 and 4 to the motors, which then work until the limit switch turns them off.

So far i have:

1) Changed RTR MTR and MTR fuses.
2) Confirmed i have full battery voltage at pins 3 and 10.
3) Confirmed i have good earth at pin 12.
4) Unplugged Retract Relay and a positive feed on pins 1 and 4 will work the motors - so wiring between Retract Relay and motors good.
5) Tried 2 different motors.
6) Confirmed Retract Relay good by trying on another car.
7) Confirmed pin 8 is earthed when stalk pulled to flash.
8 ) Confirmed pin 6 is earthed when lights operated by switch.
9) In all cases, the headlight bulbs illuminate when they should.

Over to the IMOC massiff...

[jimi]

Have you checked to see if you are getting +12v out on pins 1 & 4 of the retract relay when the headlight switch is on or flash command is given (stalk pulled)?

[Peter Gidden]

Have you checked to see if you are getting +12v out on pins 1 & 4 of the retract relay when the headlight switch is on or flash command is given (stalk pulled)?

I never get +12v out on pins 1 & 4 of the retract relay when the headlight switch is on or flash command is given (stalk pulled).

[ashley]

When you tested unplugged the retract relay and gave the motors +12v, did you do it at the motor end, or on the plug that came out of the retract relay itself? (Checking wiring integrity from relay to h/light units)

Would be worth checking the operation of the level switches, do you have continuity between Retract Relay pins 1 & 11 & 7, and pins 4 & 7 & 11 when the headlights are in mid travel? The relay needs to Ground on pin 11 or 7 to operate the motors.

Otherwise is it something mechanical?

[ashley]

Have you checked to see if you are getting +12v out on pins 1 & 4 of the retract relay when the headlight switch is on or flash command is given (stalk pulled)?

I never get +12v out on pins 1 & 4 of the retract relay when the headlight switch is on or flash command is given (stalk pulled).

This is a big clue...says the Retract Relay isn't trying to operate the motors...so must be a problem with the relay, or the inputs to it (stopping it trying to operate)...level switch inputs need checking. The wiring to/ from these does flex as the headlamps go up and down, so very possible that the looms themselves have deteriorated

[jimi]

Do you get a -12V out on 1 & 4 with the lights on ?

[jimi]

Be nice to know what the outcome was ?

[ashley]

It was the diodes in the level switch- they had failed, and I think on both headlights....and on 3 spare ones as well!

Must be the age of these cars now, and the diodes being one of those components with a limited life?

[jimi]

Good to know very unusual fault, never come across that one before on a MK1 or MK2.
I'm gobsmacked that you have 5 with the same fault, it would lead me to suspect that something was causing them to fail

Must be the age of these cars now, and the diodes being one of those components with a limited life?

I'd say no, in my professional experience I'd say a silicon diode is one of the most reliable solid state components going, a 20/30 year working life is nothing to them.

[ashley]

Wasn't my car- twas one Peter was working on, so I'm only reporting second hand...maybe something to do with the conditions the headlights are exposed to that is helping age the diodes early...dunno, maybe Peter has a better idea...