Dim Headlights

[Guest AWhite]

Right the time has come to fix my long running dim headlight problem. Unfortunately my electrical knowledge is not too hot and I've drawn a blank on this one. I've upgraded from sealed beam units to H4 but still have the same problem. Here's a few things i've tried:

 

-Checked 1 headlight straight from battery = much brighter.

-Voltage across battery with engine off 12.5v.

-Voltage across battery at idle 13.6v

-Voltage at headlight with one light unplugged 8.5v (multimeter going in the connector for unplugged headlight).

-Voltage at dipped/main beam steering column switch with lights unplugged 12.5v

-Voltage at dipped/main beam steering column switch when lights plugged in 8.5v

-Voltage at headlamp relay (with relay unplugged) 12.5v

-With 1 headlamp unplugged the other headlamp is noticeably brighter (is this normal?)

-The wiring is decent guage stuff up to about 30cm from the headlight where it goes to narrower guage. I guess this is gonna be hard to change because of the headlamp connectors. Hopefully there is not enough length of narrow to effect things?

 

Any ideas anyone on what the problem is or what to try next?

 

Thanks guys,

 

Andy

[Dave Ed]

how are the headlights wired up?

 

do you have two separate feeds to the lights ie 2 wires both with 12.5 volts from separate wires and fuses as per an original sierra loom and fuse box.

Or do you have 1 live wire feeding both lights.

 

If its the latter then the voltage drop will be equal across both ie 6 volts each giving dim lights

 

Also check your earth cables and clean them up, you might have a bad earth which causes dim lights

 

Dave

[Peter Bell]

Andy, check the connections to the headlight plug are the correct way around. they should be like this Lights I know this is the old sealed beam and stuck on sidelight but it has been known that 2 connections are swapped, the lights do work but are dim.

[Guest AWhite]

Thanks guys. The headlights are wired up to the correct connectors as per the image on the NW site.

 

From what I can see there is one cable for dipped beam and one cable for full beam coming from the switch on the steering column (the indicator stalk) I can't quite see where this splits into 2 yet. The power from this seems to come from the light switch on the right hand side of the steering column (single cable) and goes to the dipped or full beam wire depending on which position the stalk is in. This can't be right can it? The relay seems to work ok but I would have thought the right hand stalk should go through the relay and power should come from the relay.

 

Looks like you could be right then Dave, should there be 2 relays then? 1 for each headlight?

 

Cheers,

 

Andy

[Guest The Modfather]

I'd have thought that it would only have one wire feeding the two lights with them wired in series. If you have 12v going into the first lamp, you'll have 12v coming out and going to the other. I THINK?????????

Sounds more like you are either earthing out somewhere, not using a relay, and/or bad earth point.

[Redspec]

I'd have thought that it would only have one wire feeding the two lights with them wired in series. If you have 12v going into the first lamp, you'll have 12v coming out and going to the other. I THINK?????????

Sounds more like you are either earthing out somewhere, not using a relay, and/or bad earth point.

 

Parallel otherwise you will only have 6v at each of the the lamps.

 

Steve

[Dave Ed]

ok, assuming that you have a ford loom and fusebox - then there is 1 relay (Haynes page 429 item 24) dip beam relay.

this will feed battery voltage from pin 87 to one side of fuse 17 and 16 which are the dip beam fuses ( 1 per light), in theory if you have 2 fuses and 2 wires feeding 2 lamps then this is a parallel circuit. there shouldn't be a volt drop as they are individually fed from the battery and shouldn't affect each other.

 

if you have an aftermarket loom make sure that you havent wired the headlights up so that they link from one lamp to the other with a single cable.

 

does your flasher and main beam work correctly?

 

gotta mention after having read another topic post, i'm using the haynes book no. 903, just to avoid confusion.

 

Dave

[Jez Morton]

Andy,

if your going to the Cannock run/barbie on Sunday with Andi, I could take a look at it if you want I know a bit about electrickery. If not I dont mind taking a look if you can get over to Coventry.

 

Jez

[Andi]

Gotta say Andy,

Jez is a bit of a wizard with the black arts

[Guest AWhite]

Thanks Jez, might take you up on that once I've exhausted my limited knowledge.

 

@Dave - its the Ford loom and the main beam and flash all work ok all be it a bit weakly.

 

Andy

[Jez Morton]

Andy,

do you know what year the donor car was.

 

Jez

[Dave Ed]

Thanks Jez, might take you up on that once I've exhausted my limited knowledge.

 

@Dave - its the Ford loom and the main beam and flash all work ok all be it a bit weakly.

 

Andy

 

 

Right i take it that actually all of your lights are dim then, dipped and main.

 

If both the main and dipped are weak then i think that its before the fuses as thats where it splits to a parallel circuit. have you tried replacing the dipped beam relay with the driving lamp relay, they should be the same, is the relay hot to touch?

 

otherwise check your earth return to chassis from the lights. check you have a 0 ohm (clean contact to chassis, not paint) remove and clean anyway.

 

my indicators did the same thing when i rewired the front of the exmo, flashed dimly, i cleaned the earth and then they were perfect. although it was still the same earth point !

[Guest AWhite]

I've replaced the relay and its still the same. I've got a bit further though - there are 4 separate fuses and if i pull each one out it turns off one of the lights dipped LH, dipped RH and main LH and main RH so lights must be parallel and must be problem before fuse box.

 

If i feed power direct from the battery to the back of the fuse connection the lights go brighter so there must be something sapping the power before it gets to the fuses.

 

Andy

[Dave Ed]

Yep i came to the same conclusion.

I would still double check the earth first, all the lights high and low left and right use common earth.

If you can locate and clean / re-terminate the connection so that all strands are crimped then you will eliminate the earth from the equation.

 

For instance, if you have a bad earth then you wont get a full voltage drop at that point, if there is not a full voltage drop from battery (12v) to earth (0v) ie 12v total drop, then you have whats called a standing voltage (i think). Therefore you might only be dropping 8.5 volts and that is why your lights might be dim. You will still read 12v before the relay and hopefully after the relay

Look for things like scotch locks, twisted wires covered in tape, not all strands crimped together etc..

 

If Jez is a wizard at elastic trickery then utilise his experience.

 

Dave

[Dave Ed]

 

If i feed power direct from the battery to the back of the fuse connection the lights go brighter so there must be something sapping the power before it gets to the fuses.

 

Andy

 

just re-read the last post. looks like the earths are fine as battery voltage direct to the fuses increases the brightness, relay is replaced and therefore assumed a goodun. i would suggest you look at the back of the light switch gear. i'll have another look at the diagrams and have a think

 

Dave