Main beam issue on Mk2

[GTXTRA]

So -

the 16v - sidelights and dipped beam - working fine.
on main beam the inner spots work fine but the headlamps switch to side light mode.

car has a BRM headlamp loom, relays all seem fine/not blown - have tried a NOS headlamp switch, same result.

all the other mk2's go - 1 - sidelights, 2 - dipped beam, 3 - main beam on both headlamps/inner spot lamps.

thoughts? Pete?

interestingly the number 9 and 10 main beam fuses that should be 10 amps were infact 3 amp fuses.

[ianaudia4]

Sounds like a relay problem, any chance you can try a different relay from one of the other cars in your stable?

[GTXTRA]

it's the next logical course i guess, the merseyside derby got in the way of further investigations................

cheers

[bensspares]

I had something like this on mk1 with a normal loom, it turned out to be an earth problem with the loom under the bonnet.

[Nate]

have you tried changing the bulbs?

[PeteGLi]

thoughts? Pete?

interestingly the number 9 and 10 main beam fuses that should be 10 amps were infact 3 amp fuses.

I'll need to think about it when my brain has got over the mind numbingly boring Continuing Professional Development seminars I have attended today.

The fuses in the fusebox only being 3 amps should not be a problem. They will not have much current running through them, given that those circuits now only act as the 'switch'. The fuse for the main beam power, should now be between the battery and the new relay and, depending on whether the relay powers one or both bulbs, will decide its rating.

Amps = Watts divided by Volts
- so a circuit with just one 60 watt bulb would need an 8 or 10 amp fuse.
- both bulbs on the same circuit would need a minimum 15 amp fuse.

[GT Matt]

It does sound like the relay is either a) knackered or b) not switching over (caused by switching supply not present or poor relay earth) or could be as simple as both bulbs (as suggested earlier) as it isn't common for two bulbs to fail at the same time.

Check for a 12v supply at the bulb when you select main beam. If it's there, it's more than likely the bulbs. If not, start checking the relays

Hope this helps

Matt

[Nate]

don't know how the headlights are wired up with the uprated loom, as i've only had experience of uprated looms that i have built myself. i would assume there is a relay for high beam for each side of the car - i.e. left main beam and spot light are wired together, as are the right main beam and spot. this would mean it will either be a broken wire between the relay and the bulb, or the bulbs have blown

[Jay4424]

thoughts? Pete?

interestingly the number 9 and 10 main beam fuses that should be 10 amps were infact 3 amp fuses.

I'll need to think about it when my brain has got over the mind numbingly boring Continuing Professional Development seminars I have attended today.

The fuses in the fusebox only being 3 amps should not be a problem. They will not have much current running through them, given that those circuits now only act as the 'switch'. The fuse for the main beam power, should now be between the battery and the new relay and, depending on whether the relay powers one or both bulbs, will decide its rating.

Amps = Watts divided by Volts
- so a circuit with just one 60 watt bulb would need an 8 or 10 amp fuse.
- both bulbs on the same circuit would need a minimum 15 amp fuse.

Seconded. Don't be looking for the fuse in the normal place, it'll be within the new loom!

Failing that, has it been working? (something failed) or has it never worked right (wired up wrong?)

Jay.

[PeteGLi]

If the fuse to the relay is ok, then it sounds like the main beam filament may have gone in the dip/main bulb/s.
Try a bulb that you know both filaments work.

[Nate]

did you sort this one sean?

[GTXTRA]

tomorrow hopefully - will be swapping relays between the two cars with brm looms and take it from there.

[GTXTRA]

ok.
switched relays between the two brm loomed cars. made no difference to either car. 16v relays fitted to the 2- litre worked the loom fine - i.e when operating lights 1 = side-lights, 2 = dipped, 3 = main beam on both headlamps and inner spot lights.

changed both bulbs. no difference.

fitted spare indicator/main beam/flasher stalk(that had been working fine on the car it came off). no difference.

[GT Matt]

Does still sound suspiciously like switched or earth wiring at the relays rather than the relays themselves.

What's the exact set-up? Is it one relay per side of car or one relay for dipped and one relay for main beam or a single relay for the lot?


4 or 5 pin relays?

Got any photo's?

If only you were closer to Derby.................

[GTXTRA]

hi matt - its a three relay set up.

pretty sure they are 4 pin relays.

tbh - it's off to the phirm on 5th february where along with getting its new boots and a new exhaust it'll be having an mot next door - pretty sure that tim will be able to sort this for me or can always disconnect it and go back to standard for mot.