The Prince of Darkness Finally Strikes

[Webb Sledge]

Up to this point, I've been pretty luck with my car (read: no electrical problems). About 8 months ago I bought Silverstars to replace my old lights when one of them burned out. But about 4 months ago, the left Silverstar started to go dim, and now it's almost completly out, burning very dimly. I thought that Silverstars just went out quickly so I bought some new beams from VB, with replacable bulb, only its the same case. The right bulb is fine, and the left is lit, but very dimly.

Anyone know what I should go searching for? I have a OHM/Voltmeter gauge, so I can go probing around with that.

 

[RomanH]

I have had this same problem with my car except that it was the right head light.
What I did was go through the wiring starting at the affected light and look for any corrosion on the terminals. Also, give them a little tug to make sure that the wires are still connected to the terminal and have not simply corroded away. If you find any corrosion try to clean it or just replace the terminals.
My problem turned out to be the bullet connetors in between the right and the left lamp so I replaced them with AMP brand connectors because I know they are good.
I would start there. When using the voltmeter you should have the same voltage as the battery with the engine off at the head lights.
Good luck! /ubbthreads/images/graemlins/hammer.gif
Roman

 

[Banjo]

Start by checking all connections in the wiring to that lamp. It's most likley some corossion in one of the bullet connectors. Also make sure the ground connection is good.
P.S. if the bulb is dim in both high and low beam settings it's almost certainly the ground. If it's only in one setting, then go after that power circuit.

 

[sammyb]

The dipper switch (foot switch) is a common place for corrosion to set in. Like everyone else said, just start at the headlight, and work your way back. Luckily, even a TR6 is still a pretty easy color-coded system with only a few areas to investigate.

 

[dklawson]

When you are checking the connectors up front, don't hesitate about adding an additional ground wire connection for the headlights. Multiple good grounds are much better than one weak one.

As a sidebar to this, you may also want to do a little searching here and on the net for information on adding relays to your headlight circuits. This takes the demands off both the dash switch and the dimmer switch and most people report brighter headlights as well.

 

[bobh]

In a previous life when I maintained all of my friends cars I saw this fairly often. The most common fault was the ground connection. Doug's advice about adding a relay is also very good. Adding a relay may eliminate the possibility of catastrophic failure in the future.

 

[Geo Hahn]

As noted, a poor ground is a prime suspect. One clue may be if your high-beam indicator glows a bit when the low beams are on... a poor ground may cause the circuit to seek a ground thru that lamp.

 

[Brosky]

Do you have any good tips on exactly how to wire such a relay in to the circuit properly?

Thanks,

 

[myspitfire]

Yes i have the same question;as a novice how & where does one hookup a headlight relay. thanks Ken 1500 79 Spit /ubbthreads/images/graemlins/rolleyes.gif

 

[danmas]

For info on using relays, please check our website at https://www.advanceautowire.com

We sell headlight relay kits, but we have also posted the wiring diagrams for them on the web site which you can use freely to make your own if you prefer.

 

[Webb Sledge]

My left headlight stays dim whether in high or low beams. It doesn't really get any brighter at all when I turn the highs on. If anything it dims a little bit more.

 

[Dave Russell]

See above about grounding.
D

 

[dklawson]

I suggest that you look at your car's wiring diagram along with the links posted above regarding relay panels.

Succinctly however, LBCs typically use a common wire to the dimmer switch. From the dimmer, the blue/red wire goes to the low beams and the blue/white wire goes to the high beams. Disconnect the headlights up front where their bullet connectors connect to the wires from the dimmer. My preference is to put a relay on each of these circuits (2 relays). Each relay has a ground connection to one side of its coil. The other side of its coil is connected to the bullet connector on the blue/red or blue/white wire (as appropriate) coming from the dimmer switch. Thus, your dimmer switch is powering the relays on and off. Each relay has one of its contacts connected by a fuse to the brown (always hot) post of the solenoid. The OTHER remaining relay contact goes off to the blue/red or blue/white wires of the headlights. I use Bosch style ISO relays as they are readily available from local parts stores and online. As mentioned, you can buy these harnesses or make your own. Bullet connectors and related components are available from most British parts vendors and from www.britishwiring.com

 

[piman]

Hello Doug,

relays do help a little, but not if the earth is poor, and this seems to be the problem here. If both the main and dip beams are weak then the common link is the lamp earth.

Alec

 

[Keoke]

Well now that is one way to do it DK. However, because the dimmer switch is always in one position or the other initially aren't you still passing the lights load current through the dash switch when the lights are energized.??---Keoke

 

[dklawson]

Keoke, with the relays added the power passing through the dimmer switch is only powering the relay coils, milliamps instead of amps. The contacts for the relays (which then feed the head lamps) are connected by fused wires to the starter solenoid so the main lamp power comes directly through that connection, not through the dash or dimmer switches. My description matches that provided by Dan's link above with the exception of where I placed my fuses.

Piman, please notice that in my first post I suggested running additional, clean grounds. Relays were suggested in addition to the improved ground.

EDIT: Keoke, I was thinking about this more after my last post and it occured to me that it's worth mentioning that... once relays are installed they carry the lion's share of the current. However, the dash switch will still be carrying the current for the running lights. This will be much less than head lamp current... but it is obviously more than the relay coil current alone.