High beam lights stopped working

[JDubya]

Hi All,

The lights on my 72 Mk1 Stag worked perfectly for the first few weeks of ownership then suddenly the high beam lights have stopped functioning. The light in the warning lamp cluster comes on but no change in the lights - the dipped beam, indicators and parking lights are all working fine.

I have checked all fuses and no problems there. From the wiring diagram it implies that the relay must be working for the warning lamp to illuminate. I haven't specifically checked the bulbs but would seem odd for both to blow at about the same time.

Any thoughts ??

[mike@thenook]

I think I'd start by removing one of the high beam light units and see if there is any power going to it. It may be a break in the cable supplying those lights. The dash light that lights to tell main beam is on is not dependent on the bulbs actually working.

cheers

[JDubya]

I think I'd start by removing one of the high beam light units and see if there is any power going to it. It may be a break in the cable supplying those lights. The dash light that lights to tell main beam is on is not dependent on the bulbs actually working.

cheers

Thanks Mike - will do. I guess I need to trace the wires from the high beam relay also.

Cheers

[mallardstag]

There is no relay in the headlamp circuit. Current comes straight from the battery to the main light switch and then through the dip/main/flash switch to the main beam warning lamp and the main beam fuses. If both your main beams have failed but the blue warning light is on then you probably have more than one fault. Check both main beam fuses and bulbs for failure. With the main beams switched on do you have 12V on both sides of both fuses and at the back of both bulbs?

Simon

[milothedog]

There is no relay in the headlamp circuit. Current comes straight from the battery to the main light switch and then through the dip/main/flash switch to the main beam warning lamp and the main beam fuses. If both your main beams have failed but the blue warning light is on then you probably have more than one fault. Check both main beam fuses and bulbs for failure. With the main beams switched on do you have

12V on both sides of both fuses

and at the back of both bulbs?

Simon

Can I just add and to avoid confusion. That the above test on the fuse box are with the Neg probe of the meter earthed, not one on each side of the fuse holder


Having said that, if you do use the volt meter with each probe on either end of the fuse holder with the lights on and fuse in place you shouldn't see no more that 0.5v on the meter, anymore than that suggests a bad connection with the fuse in the holder


Hope you don't mind Simon, its just the way I read your reply I thought may lead to a false diagnosis.

Ian

[mallardstag]

Hope you don't mind Simon

Ian,

I don't mind at all - you are quite correct in clarifying this.
Simon

[dasadrew]

I had an almost identical problem before I started my resto. Can't remember about the blue light, but the main beam worked, then it came on for a split second a few times, and finally it gave up the ghost completely. In my case the switch was completely fried internally. It seems that the few times I tried, a micro gap in the fried contacts created an arc which made contact, then burned through a split second later until after a few cycles everything was totally FU.

Drew

[mallardstag]

I had an almost identical problem before I started my resto. Can't remember about the blue light, but the main beam worked, then it came on for a split second a few times, and finally it gave up the ghost completely. In my case the switch was completely fried internally. It seems that the few times I tried, a micro gap in the fried contacts created an arc which made contact, then burned through a split second later until after a few cycles everything was totally FU.
Drew

Drew,

If this were the problem then the blue warning light would not come on (assuming it's all correctly wired). The OP stated that the warning light is working so the problem(s) should be downstream of the fuses.

Simon

[Mike Stevens]

Or between the dip switch and the fuses. Or perhaps more precisely, between where the warning lamp wire comes out the harness and the fuses!

(Or just maybe both headlamps have blown....!)

Cheers,
Mike.

[mallardstag]

Or between the dip switch and the fuses. Or perhaps more precisely, between where the warning lamp wire comes out the harness and the fuses!

(Or just maybe both headlamps have blown....!)

Cheers,
Mike.

Mike,

From the dip/flash switch the wire routes to fuse 11, from there to fuse 13 and from there to the warning lamp. This should mean that if the warning lamp is working there is feed to both fuseholders.

Simon

[Mike Stevens]

Thanks Simon. That's the problem with having just the wiring diagram on the work PC, not the whole car to look at!

Agree with you then. Maybe just poor fuses. A good going through with a voltmeter should find where the break is then!

Cheers,
Mike.

[dasadrew]

Yes Simon, you're right. I was mobile on the iPhone but just checked my wiring diagram now. Additionally on my Mk2, there is only one fuse (6) for main beam of both the outer headlights. Fuse 5 does the inner spots. Both fuses get their supply from the wire coming from the switch so, if the spots work but the main beam doesn't, then it seems to be downstream. The bridge across the two fuses also supplies the warning light so it seems that the upstream part seems to be ok. Maybe the bullet connector just by the headlights where the blue/white feed goes to one light and branches off to the second one.

Drew

[mallardstag]

Maybe the bullet connector just by the headlights where the blue/white feed goes to one light and branches off to the second one.
Drew

Drew,

Not sure about a MK2 but the OP's car is a MK1 and that has one fuse for each headlight and no intermediate connectors between the fuse and the lamp, hence the suspicion that there is more than one fault (or non-standard wiring).

Simon

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[dasadrew]

This is interesting! Did the Mk 1 not have a "main Beam" filament in the outer headlights? On the diagram there seem to be two "filaments" missing??

Drew

[DJT]

This is interesting! Did the Mk 1 not have a "main Beam" filament in the outer headlights? On the diagram there seem to be two "filaments" missing??

Drew

All the home market Stags had 4 H1 single-filament bulbs. On main beam, the outer lights stayed on dip and the inners came on as mains.