headlight/mainbeams

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headlight/mainbeams

Postby billybob » Thu Nov 19, 2015 9:01 am

Hi all,

so I will keep the midas and get it through another MOT come February (redundancy scare has gone away for a bit!)

Anyways...after the freak rain storm last night there is a weird thing going on with the headlights and mainbeam. I will try to describe it in a nutshell:

side lights on and working fine, headlights work okay but passenger side is dimmer than drivers side, mainbeam all come on okay. The problem comes when I try to turn off the main beam- they won't turn off unless I kill the headlights as well!

I am thinking that a relay must have got wet so the first question for me is, is only one relay used on each side for both headlights and mainbeam lights? The only other thing I can think of is the main beam switch in the stalk but I think given the weather its more likely to be underneath the car somewhere by the lights themselves!

Thanks all. :D
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Re: headlight/mainbeams

Postby Rich » Thu Nov 19, 2015 12:02 pm

From memory it is a single relay for high beam.
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Re: headlight/mainbeams

Postby billybob » Thu Nov 19, 2015 2:16 pm

that's encouraging, it means that only one relay would have to be faulty to cause the issue. The ironic thing is that by the time I get home it will be too dark to check the lights :D

I was thinking that if water has got in then the relay coil might be a bit sticky (just a theory mind so please feel free to dismiss!)

Is the relay for the mainbeam/headlights just a standard 4 pin high voltage/amperage jobby?
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Re: headlight/mainbeams

Postby billybob » Thu Nov 19, 2015 2:18 pm

hang on I may have misinterpreted your post :/

are you saying one relay for headlights and a separate one for main beam?
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Re: headlight/mainbeams

Postby Rich » Thu Nov 19, 2015 5:33 pm

billybob wrote:hang on I may have misinterpreted your post :/

are you saying one relay for headlights and a separate one for main beam?


On mine I'm pretty sure there is a general 'lights' relay on the main board and the main beam/drive lights are switched by a separate relay which is under the bonnet.
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Re: headlight/mainbeams

Postby billybob » Thu Nov 19, 2015 6:46 pm

yes I think that is what I have, I will check the one on the main board first and then the individual ones underneath by the lights.
Weirdly the lights started behaving again when i sat on the drive and increased the revs a bit so I may also be contending with something alternator (ish) as well!

thanks pal
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Re: headlight/mainbeams

Postby Rich » Thu Nov 19, 2015 9:27 pm

Alternator is another option, I've had nagging problems on the GTM with the high beam being dimmer than the low beam, the radio packing up and the battery running down over two or three days.

At no point did the charge light come on, but a multi meter across the terminals showed 12.5V when the car was running, revving it made no difference. One alternator later (swine of a job on the GTM) and I've got bright lights and 14V across the terminals at idle.
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Re: headlight/mainbeams

Postby billybob » Thu Nov 19, 2015 9:54 pm

very interesting. Could be on to something with that. Will have to get the old multimeter out!
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Re: headlight/mainbeams

Postby billybob » Fri Nov 20, 2015 8:27 am

okay so I noticed something different again this morning on the way to work. I still have the same main beam problem but also, when I turn the side lights on the drivers side headlight also comes on with them. Then when I put the main beam on, all the lights come on but the passenger side is dimmer. Turning main beam off again just removes part of the passenger headlight.....

all very weird but there is clearly something up with the passenger headlight. If something has blown in the passenger headlight unit could this be causing all of the weirdness?

So next question, what sealed beam unit would I have to purchase for the headlight? It looks smaller than morris minor units to me :?
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Re: headlight/mainbeams

Postby kelvink » Fri Nov 20, 2015 11:10 am

Have you had a good look at the earthing? It sounds a bit to me like current is trying to find alternate routes to earth.
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