Driver's side headlight won't light

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john in kzoo
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Driver's side headlight won't light

Post by john in kzoo » Thu Jan 02, 2020 4:00 pm

Hey Guys...Happy new year

'15 touring, using the mag for headlights, it's wired stock(series). I can't get the driver's side headlight to light. Passenger side works fine. Tried known good bulbs still doesn't light. Thoughts...

Thanks

John


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Re: Driver's side headlight won't light

Post by Mustang1964s » Thu Jan 02, 2020 4:18 pm

Get a test light and start tracing back the wire.
Check the test light at the battery to make sure the test light works.
This little check first will save hours of checking. Don't ask how I know.


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Re: Driver's side headlight won't light

Post by 2nighthawks » Thu Jan 02, 2020 4:29 pm

I've had a sort of "off & on" problem with that on a couple different Model T's and also a Model A, and invariably, it's due to a bad ground!

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Re: Driver's side headlight won't light

Post by john in kzoo » Thu Jan 02, 2020 4:44 pm

Thanks Guys. It seems like if it were the ground then neither light would light. I have taken the bulb from the passenger side that just worked, placed it in the driver's side, put another bulb in the passenger side... the result was the passenger side worked and the driver's side did not....


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Re: Driver's side headlight won't light

Post by Kenny Edmondson » Thu Jan 02, 2020 5:11 pm

They are supposed to wired parallel not series. I assume you’re mistaken on the term. You have a ground issue or power issue. Are you getting power and ground to the light thats not working? The ground is through the frame and light housing the two wires are low and high beam. Run a ground from the battery up near the headlight and check for power on the low and high beam. Remember that you have to have a load to show up a voltage drop. So you may show voltage with a DVOM but a test light may not light up.

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Re: Driver's side headlight won't light

Post by TRDxB2 » Thu Jan 02, 2020 5:21 pm

Maybe a loose (or dirty) connection in the black plug. Remove the plug and check the voltage on its output end, if okay then do the same for the headlight socket inside the bucket. If not okay then check connections back towards the source.


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Re: Driver's side headlight won't light

Post by Norman Kling » Thu Jan 02, 2020 5:26 pm

Pull out the bulb and use your test light on the conductor inside the socket. One lead to ground and the other to the contact inside the socket. If your test lamp lights up, you have either a problem with the socket or the ground. Sometimes the spring inside the socket under the contact has gotten weak and does not make a good contact. At times this can be remedied by adding a bit of solder to the contact at the back of the bulb. The most common cause of the problem is the ground connection. The actual contact with the outside of the socket with the light frame can be corroded or loose. Or the connection with the light bracket at the frame can be corroded or loose. Anyway this can be added to what was said above.
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Re: Driver's side headlight won't light

Post by Corey Walker » Thu Jan 02, 2020 5:29 pm

Either the passenger side headlight socket is grounded or there is a short to ground somewhere in the wire that goes across to the drivers side. If the drivers side bulb was blown neither would work.
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Re: Driver's side headlight won't light

Post by Roz » Thu Jan 02, 2020 5:42 pm

He is having the problem with magneto headlights. They are wired in series. I don’t quite understand how one can work and one not since the current has to pass through both. If one burned out, neither one lights. Seems like it would have to be a ground problem.
Last edited by Roz on Thu Jan 02, 2020 5:45 pm, edited 2 times in total.

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Re: Driver's side headlight won't light

Post by Susanne » Thu Jan 02, 2020 5:43 pm

Corey Walker wrote:
Thu Jan 02, 2020 5:29 pm
Either the passenger side headlight socket is grounded or there is a short to ground somewhere in the wire that goes across to the drivers side. If the drivers side bulb was blown neither would work.
Yep, this. One of the downfalls of a '15 running stock lights is normally if you lose one, you lose both. My guess is you have a ground issue in the crosswire in the radiator tube (they chafe and wear insulation at the end of the tube)... that's why the right one works - it's a complete circuit from the switch to the light, through the light and grounded at the wire, and not making it to the left headlight.

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Re: Driver's side headlight won't light

Post by Steve Jelf » Thu Jan 02, 2020 6:00 pm

They are supposed to wired parallel not series.

Come on, guys. We're takling 1915 here. Mag lights. Of course they're wired in series, just like those notorious Christmas tree lights that all go out when one dies. I'm an electronic moron, and even I understand this.
WIRING 2.jpg
If John's lighting setup is stock, the circuit goes like this: From the switch to one contact on the right side bulb; through the filament to the other contact on that bulb; through the wire to one contact on the left side bulb; through the filament to the other contact on that bulb; through the wire to ground at the radiator support.

Why didn't I mention the sockets? Because all they do is hold the bulb bases in place. They're not part of the circuit.

My guess is that John's left light has a short between the two contacts behind the bulb, in which case the current is taking the easiest path, through that short to the ground wire and skipping the bulb. Either that, or there's a ground somewhere between the right and left lights.
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Re: Driver's side headlight won't light

Post by Oldav8tor » Thu Jan 02, 2020 6:51 pm

I think Steve might be onto something. I converted my magneto headlights to LED's and wired the sockets in parallel. No matter what I tried, the right one would not work. I got a new socket and no problems ever since. It seemed to check out OK but put a bulb in and it was a no-go. Unfortunately, the only way to see what is going on inside between the socket and bulb contacts is to cut the socket open.
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Re: Driver's side headlight won't light

Post by Scott_Conger » Thu Jan 02, 2020 7:31 pm

The short to ground guys are nearly certainly correct. On the bright side (sorry 'bout that), that one light is probably REALLY bright. :lol:
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Re: Driver's side headlight won't light

Post by Steve Jelf » Thu Jan 02, 2020 9:01 pm

No, Scott. No mag light is really bright. :D
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Re: Driver's side headlight won't light

Post by Scott_Conger » Thu Jan 02, 2020 9:51 pm

So, "Dim Bulb" is one of the more appropriate metaphores, eh?
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Re: Driver's side headlight won't light

Post by CudaMan » Thu Jan 02, 2020 11:27 pm

There's a light on this T that won't light on one side!
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Re: Driver's side headlight won't light

Post by WayneJ » Fri Jan 03, 2020 5:20 am

This is a timely topic for me as I am having the exact same problem on my 1915. I will look at the wire that connects the right headlight to the left, to see if it is shorting out where it passes through the radiator.
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Re: Driver's side headlight won't light

Post by Kenny Edmondson » Fri Jan 03, 2020 7:25 am

If the drivers side bulbs are removed, does the right side still stay lit up?

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Re: Driver's side headlight won't light

Post by john in kzoo » Fri Jan 03, 2020 7:54 am

Hey Steve, Yes my T is wired exactly as laid out in the diagram (stock). I have some wire and a test light, I'll play with it this weekend and see what I find. They worked fine at OCF (although useless with 24V bulbs) The ones I'm trying are older bulbs that I picked up so it may be a contact issue, or lack there of, in the socket assembly, as suggested. Thanks to all for the leads...

John

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Re: Driver's side headlight won't light

Post by Steve Jelf » Fri Jan 03, 2020 10:53 am

Yes, the 24v bulbs allegedly for use in mag lights are useless. Fortunately original bulbs can be found at swap meets. There is a problem with those too, though. In some of them the cement holding the glass in the base has let go, so when you try to install the bulb in the socket the glass twists in the base and the bulb is ruined. This is pretty annoying when you're on a trip and all seven of your replacement bulbs suffer installation destruction. You can count on all the local parts stores to have nothing that will work. One of my winter projects will be applying new glue to some bulbs to see if that cures the problem.

IMG_2981 copy.JPG
Mag bulbs are two-contact, even pin. The real ones are supposed to be 9v, but I find that bulbs marked 6-8v in this configuration last pretty well and are very common.
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Re: Driver's side headlight won't light

Post by john in kzoo » Fri Jan 03, 2020 11:28 am

Those pictures are some of the ones I picked up as well

John

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Re: Driver's side headlight won't light

Post by Susanne » Fri Jan 03, 2020 1:20 pm

6-8 volts are battery headlights.

9 volts are early (series) Mag Headlights (just don't rev the motor too far at night)...

18 volts are the same, but wired parallel, not series.

24 volts are aircraft lights... they work, but man, are they dim. I ran one in my taillight conversion using a wire off my headlight switch, and it was just about right for a taillight.

Waiting to see if anyone has the glue issue figured out... I have a box of NOS lights that I'm not going to mess with until we can figure out how to hold the glass envelope to the metal ring...


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Re: Driver's side headlight won't light

Post by Piewagon » Fri Jan 03, 2020 3:53 pm

First off make sure you in fact have magneto type bulbs since at a glance they may not be what you think they are. Magneto type bulbs MUST have 2 connections and NEITHER of those connections at the bulb will show any continuity to the outer part of the lamp base. There should be ONLY 2 filament in the bulb. Next check the socket to make sure it has 2 connections but also make sure that the bulb will be touching both connections when it is inserted since there are some BOGUS repro 15 type plugs that have the contacts 90 degrees rotated from what the bulb needs. I think you simply might have a wrong type bulb or socket since I have seen both of them while playing with my 15 headlights. I converted mine to parallel so that I would not have to worry about suddenly having ZERO headlights one one burned out or came loose.

You probably can solve this with only your eyes on it. What parts of your setup are NEW and REPRODUCTION since just because somebody says it is made for 1915 - mine were NOT and I found some NOS parts that then did work but I then deliberately changed the wiring to parallel bulbs. Since there will still be 2 wires going into each light base with either configuration nobody can tell if you have it series or parallel unless you unscrew the base cover insulator.

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Re: Driver's side headlight won't light

Post by George Mills » Fri Jan 03, 2020 3:58 pm

Susanne,

Lightly dust the seam area...

Dribble Super Glue at the seam and let it wick around all by itself...

Have done this now on every old bulb (read shellac seal) that I get my hands on. Keeping fingers crossed, I’m still batting a thousand since I started that.

One other word of wisdom...if the existing shellac appears to be flakey...I toss them as chances are a vacuum seal has let go too. They’ll light if you seal them...brighter than normal too...but then they go pfffft relatively short time.

As to the original poster...heed Kenny latest advice...pull the driver side bulb out. If the passenger side stays lit, you have a short probably BEFORE the driver lamp. Now go trouble shoot it.

I AM having issue with how/what you report tho. If you have but one lamp lit, and it is a 9 V lamp, and there isn’t enough downstream resistance to factor in....it should last all of about 2 seconds at anything more than a low idle

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Re: Driver's side headlight won't light

Post by George Mills » Fri Jan 03, 2020 4:59 pm

Further to Steve and his 6-8V comment. I'm not sure of what the lamp number may be...but at a 8V rating (the upper end of the rating) this gives a combined 16 V when connected in series which the 15-16 were.

As Steve has advised, these seem to work fairly well based on his finds and experiences.

Here is why...

A T with a decent mag and setting would put out 16V at 650 RPM...

This is a tad over 16 MPH with 3.63. rear / is 19.5 MPH with a 3.00

So they actually get brighter quicker than the 18 V factory arrangement.

Now for the cute part. Steve tries to go 20mph with 3.63 rear? The lamp actually puts out 50% more candlepower than originally designed for...at an increase in amps of around 7%...but the lamp life derates to 25% of original rating. Which even if originally rated at 40 hours would still be 10! WooHoo.

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Re: Driver's side headlight won't light

Post by JEC » Fri Jan 03, 2020 7:44 pm

I'm not sure how hot the bulbs get but we use furnace cement to glue the base to the glass on vacuum tubes.

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Re: Driver's side headlight won't light

Post by john in kzoo » Mon Jan 06, 2020 7:31 am

George,

Driver's side is pulled the passenger side goes out

Thanks

John

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Re: Driver's side headlight won't light

Post by George Mills » Mon Jan 06, 2020 8:39 am

PROGRESS...

As Yogi would say, when it comes to the fork in the road----take it.

Apparently, your wiring might be OK, at least voltage was passing through the unlit lamp before finding the end of the line ground! Thus providing also the ground needed for the passenger side to light.

I now suspect that you have either 18V or 24V lamps, or even higher, or a mixture of both. Here's why.

In theory, that driver lamp is 'lit' but you don't see it yet! A buss voltage of greater than 50% of the lamp rating is usually needed to make the transition from resistor into glow. Up until that point, the filament is only acting as a resistor in the circuit. (Why your other side manages to work, there is voltage passing thru the driver side filament, just not enough to get a glow going.)

If you have swapped the lamps side-to-side and the problem stays...then the above doesn't hold true and I'm just as lost as before.

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Re: Driver's side headlight won't light

Post by WayneJ » Mon Jan 06, 2020 9:20 am

On my car, when I removed the driver's side bulb, the passenger side headlight still remained lite.
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Re: Driver's side headlight won't light

Post by Steve Jelf » Mon Jan 06, 2020 10:19 am

On my car, when I removed the driver's side bulb, the passenger side headlight still remained lite.

Sounds like your wiring is not stock or there is a short.
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Re: Driver's side headlight won't light

Post by WayneJ » Mon Jan 06, 2020 12:59 pm

I am assuming a short, and/or a bad thimble, as I have stock wiring and both headlights worked up until last October. Next, I will replace the wire that runs between the two headlights.
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Re: Driver's side headlight won't light

Post by Steve Jelf » Mon Jan 06, 2020 2:12 pm

I will replace the wire that runs between the two headlights.

Check it for continuity first. It may be OK.
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Re: Driver's side headlight won't light

Post by WayneJ » Thu Jan 09, 2020 1:18 pm

My T is a "Cyclops" no more. I now have two working headlights. I switched the bulbs from one side to the other, and now they both work. I suspect the driver side bulb wasn't making a good contact, and so the passenger side bulb found an errant ground. Switching the bulbs must have reestablished a good contact in both bulbs, since now they both work.
Headlights.jpg
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Re: Driver's side headlight won't light

Post by CudaMan » Thu Jan 09, 2020 1:27 pm

Glad you fixed it and thanks for providing closure for this thread! :)
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Re: Driver's side headlight won't light

Post by WayneJ » Thu Jan 09, 2020 2:15 pm

Actually, there were two us 1915 owners with the same problem, I don't believe the original posters problem has been resolved.
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