One headlight slightly dimmer, JWest Relay kit Installed
 

Hello,

I have an '87 911 and the JWest relay kit is installed. I have a slightly dimmer drivers side headlight than the passenger side. I thought it might be the bulb, so I've replaced it, but the bulb wasn't at fault. It seems like the high beams are equally bright side-to-side, so it may just be a problem with the low-beam circuit.

Has anyone had this problem even with the relay kit installed? The contacts look good in the headlight bucket, with dielectric grease to prevent corrosion. Everything seems solid and secure. On a side note, I'm using the H5 to H4 convertor harnesses in the buckets.

I have a voltmeter, but I'm unsure of what to test back at the fuse panel to figure this out. Please point me in the right direction.

Thanks.

Try cleaning the fuse holders and the ground.

Added to of those kits and not a problem like that with either. I would check all your connections - tug on them to make sure they are secure, going to that side.

Same brand bulbs? Get a jumper wire and ground the brown wire at the plug to battery ground and see if it improves.

But he said that the high beams are equally bright, probably that is not a ground problem.
I suspect a bad connection in the low beam circuit, follow RSBob instructions.

Switch bulbs left to right to rule out a bad bulb.

Ok, thanks guys. I am going to try to go step by step through the wiring and see if anything seems wrong. I am pretty sure that the high beams seem equally as bright, but will double check. It's a bit easier to tell with the low beam.

I've tried two different sets of bulbs and the pass. side is always slightly dimmer so bulbs are totally ruled out now.

I'll check the fuse holders and the ground. When you install the relays, is the ground from the JWest kit is THE ground for the whole headlight system now? If I remember correctly, this is going to the negative terminal on the battery.

I could try jumpering the ground at the plug temporarily as a test like John Walker suggested.

Is it possible that it could be something with the relay itself?

There are ground points in the headlight area.

Had a really slow blinker on my '86 until I ran a new ground wire which cured it. John Walker is probably right about it being a fuzzy ground....

Does each headlight harness have its own ground? If so, where are these ground points? Are they in the trunk or do I need to look up under the car behind the headlight buckets?

Dim light
 

Check the voltage going to each headlight. You probably just have a bad wire or connector causing some resistance.

For your '87 front lighting harness, the grounds run back in the harness from each of the lamp sockets to meet up with the ground from the horn relay, where they are either crimped and/or soldered together with one larger groundwork that comes back through the harness and exits it by the main grounding lug for the negative battery post and is grounded on that stud.

Ok, so I went through and checked as much as I could visually and by tugging connections. I haven't had a chance to test voltage at the connector yet. Voltage at the fuses was identical on left and right circuits of course.

The wiring is so tightly packed in the battery area that I can barely even see the ground point there under the wires. If the ground is the problem here, I'm not sure it would be easily fixable, and I'd be better off supplementing the ground in the headlight bucket rather than dissecting what's there and making a mess of the harnesses. If there is a problem on the 12v wire, again I don't know how I'd find where the problem is. I can see the wire coming off the fuse panel, and then it disappears into a crazy group of wires and then I find it again in the bucket on the connector.

Everything looks good visually and seems secure. Fuses and holders are clean. If the problem isn't the ground once I get a chance to jumper that, I may just have to live with this since it's only slightly dimmer on one side, there's still plenty of light. I don't want to start hacking up the factory wiring.

Clean the connection points that are easily accessible. Use Deoxit ( Radio Shack sells it) as a cleaner.
You say you are using an H5 to H4 adapter , check if there is a good connection.
I had a problem with one of these adapters H4 to H5.
Follow John Walker's instructions jump the ground at the headlight connector/adapter with a suitable cable and see what happens.
http://forums.pelicanparts.com/uploa...1459535790.jpg

This is where you should have started, backwards from the source of the problem. If you don't see a voltage difference there, then... well then clean your lens. ;)

Ok, well I got to the bottom of the problem after some detective work with the multimeter. I was testing resistances over the wires, and checking voltages and I narrowed it down to something between the old H5 connector and the connector that goes onto the H4 bulb. I'm not sure why but I guess one of the wires wasn't sitting right in the H5 connector, and after getting them out and resetting them, things seem better now. They looked to be in their proper places in the connector, but I guess they weren't situated just right. Honestly, I don't know why that kind of connector is supposed to be an improvement over the old school and more robust H4 connector.

Thanks for the help everyone, and thanks for the patience. I should have done more detective work with the multimeter to begin with.