A12 headlights super dim

[justavillain]

I was driving my A12 a couple months back and when I turned on the headlights I had 1 dim but useable, 3 super dim, high beam or low didn't change much. They are fully lit but they are not worth anything driving wise. I believe all of them are replaced with Sullivan (Sylvania?) ones not long ago I know for sure 2 of them 1 on each side I replaced apx a year and half ago and it was ok then. the dashboard is lit to its normal brightness. the plugs are tight and the grounds are in the factory location but I did not check them yet. I was looking to see what the hive mind may have other than a ground and hot wire. If I remember correctly the headlights are powered by the dash board and curious if something in there could be the issue. the car is far from factory as far as most of it goes so tracking down wires might be a bit of a trick but I do have a multimeter, power probe and their tracer and a little bit of knowledge of these cars if that helps!

I can grab a photo of anything needed

 

[Dave6T4]

Check your ground wire to see if it is making good contact. There could be paint under it. Located on the rad cradle near the battery.

 

[Dennis H]

Characteristic. Hit the gas they brighten somewhat. I have them too, but no A12. It’s part of the experience. And fear.

 

[R413]

The paint on the metal will not bother the ground. The ground connection is made from the bolt head to the terminal, and to the body through the threads of the bolt.

The factory never removed paint at grounds and they made millions of cars that made it through warranty just fine.

Remove a headlamp and check voltage at the plug in connector. Use the ground wire at the connector, then check using the ground at battery to see if the voltage changes. Have the engine running ar 1200 RPM when you do this to simulate driving. Compare volts at connector to battery voltage.

Floor dimmer switch is first component to check or install a substitute and try it again.

 

[Bird 426]

Or the bulkhead connector. After you find the problem, maybe get a crackedback wiring harness for your headlights or one that does the same. I have them on all 3 of my cars.

 

[justavillain]

I'll dig into the voltage and see if I get a drop or a change. I'll verify there is a solid ground the car does shake a lot so it could be loose. it oddly does not change when off idle. I'll pull the book out and check the bulkhead. I do have a stand alone harness that I bought online somewhere but I didn't install it, with the relays and needing a direct battery mount and I already have an electric fan, and MSD set up on the battery. I might dig it out and give it a try if I can't find a voltage change.

should it be 12v or closer to the 14 that the alt puts out when off idle?

 

[R413]

System voltage, or darn close. You compare it to the battery volts.
Should be low/mid 14's
A fully charged battery is 12.6
What is your charging voltage? Maybe it's not charging and that's why the lights are dim?

 

[justavillain]

System voltage, or darn close. You compare it to the battery volts.
Should be low/mid 14's
A fully charged battery is 12.6
What is your charging voltage? Maybe it's not charging and that's why the lights are dim?

last I checked it was around 14 something. So I have a 1 wire alt and it is direct to battery no voltage reg. when I did have the voltage reg hooked up the dash read good but the battery would not get a charge. I put a new one on and still didn't charge. I can try another one. I also do not have a ballast resistor since I'm running the MSD I have a dual 10g wire in its place.

I just looked through the service manual and I didn't see voltages or resistance. it did say it could be high resistance in the circuit. is there an area in a manual that plays out what should be the acceptable range? I was attempting to find the location of the bulk head connector.

 

[Speedbird]

1. What you are looking for is avialble voltage UNDER LOAD. Power whatever item you want to check and measure the voltage available to it at the connection.
The ground is best checked by visual method. Or supply the item in question with a KNOWN good ground and look for changes in operation.

2. Your bulkhead connects are shown on these prints for each one (Ignore my black dots. I made splices)
I happen to be in the process of cleaning up the factory 69 prints specific to my RR. (Deleting not installed items that clutter the prints.)
So, I'll post this for reference. I assume it's the same.

You say your car has had someone working on the wiring? I hate those situations.
What you might need to know is that the headlights are "independent" of other lighting.
In other words they are always hot off either the battery or alternator through a dedicated terminal on the headlamp switch (L2-16LGN).
Right picture. Upper right quadrant.
You will find the "feed" to the switch on the left picture in the middle. (Splice of five wires. L1-16K* B1)
That splice would not normally cause a problem for power. It's a solder splice.
The power to the headlamps then goes directly from the dash switch to the foot switch and on to the bulkhead as someone previously stated.
And since the headlight power is all through that dash switch, it is a notorious problem due to high current.
The switch degrades. That MAY not be your problem. But I'll throw that out there.
(There is a common modification using Bosch relays that changes this. You may be aware of that.)
Your main wires to feed power in and out are R6 -12BK at P and A1 12R at J.

 

[justavillain]

thank you for those prints I will work on pin testing the bulk head and load testing the switch and headlight circuits. I had a bad electric problem with my Duramax a few years ago so I have a ton of ground straps that I can place to see if that changes anything.

The car is on its 3rd or 4th motor and not the OE block. when I got it it was already "messaged" with an MSD system and cobbled parts. I got it running and slowly been fixing the gremlins and having to put 2 motors in it my self (one was an old block that we bored over but the shop never checked core shift and blew a hole in 2 cylinders on break in) I have dual electric fans that are using an LS3 harness from painless to control them and made a few adjustments on the wiring to get them to work right myself.

I'll test these areas this weekend (in the middle of a snow storm here so the shops is cold) and I have the aux harness that they say takes the load off the dash I can try and throw that in as a bypass for testing also.

one other question I have is, if I have 12v at the lights or close to it would switching to LED headlights help? they would be lower draw on the circuit.

 

[Dennis H]

Be gentle with Bulkhead Connectors. Brittle. I just spray an entire can of Electrical Contact cleaner on mine and call it a day.

 

[justavillain]

I haven't ran the car at night much, should only 2 of the bulbs be lit in low beam? right now all 4 are on no matter what and when I click the high beam floor switch they all stay lit too but the one "bright" one changes the output like a highbeam would.

 

[Dennis H]

2 outside low beam.

 

[Speedbird]

Check the foot switch. Only one wire out should have power at at time.
Lt. Green is from the headlight switch.
Per the prints of "front lighting", violet with tracer feeds the outboard low lamp filaments.
Red wire feed all four lamp high filaments. Low beam filaments in outboard lamps goes out on high beam selection.

Note. Black wire AT the headlamp sockets is ground.
X and Y are the connections at the bulkhead. But I'm thinking switch problem.

 

[justavillain]

All 4 lights are on no matter high or low. I have a new foot switch on order it was a whole 11$ I’ll tear into the wiring tomorrow after work. One thing I can do is power the circuits independently with my power probe and test each light and or part on its own. Plus pull the normal data with the multimeter

The dash switch is a whole other issue If that is bad. Idk about pulling the dash open to get to it. Plus the 170$ bill on the switch.

 

[Speedbird]

Would not worry about dash switch based on symptoms.

 

[Bird 426]

Sounds to me to be replace wiring harnesses on 56 year old car. Headlight switch looks to be 40-50 dollars . Shouldn't have to pull the dash to do that.

 

[dadsbee]

foot dimmer switch is stuck on high beam and crusty... simple as that!