Headlight bulbs blown

T

tribouboys

Senior Member
I guess I need some help from the more experienced. I recently installed a new harness from the base of the steering column to the headlights and it seems the head light bulbs have blown out with the exception of the drivers high beam. Any thoughts on where I should start looking for the problem. One thing I will add my cut out seems to be sticking when I shut the car off and I just touch the starter button and it goes right back to zero. Are these issues related??
 
I am guessing that they are related. The sticking cutout was probably overcharging before you changed the harness but the old harness had enough resistance to keep the bulbs from blowing out. Hopefully you will get other answers to contemplate.
 
Get a good cutout before trying any more bulbs. The charging circuit needs a good complete circuit to the battery, or the generator can put out up to 40 volts. This is another good reason to use an electronic voltage regulator, so the voltage leaving the generator is always at a safe controlled amount.
 
Tom Wesenberg said:
Get a good cutout before trying any more bulbs. The charging circuit needs a good complete circuit to the battery, or the generator can put out up to 40 volts. This is another good reason to use an electronic voltage regulator, so the voltage leaving the generator is always at a safe controlled amount.
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The cut out was replaced at the same time the harness was replaced. The cutout I bought was from Mac's# A10505F. I think I will replace the cutout again on your suggestion but with a diode version. Any comments on the diode cutout??? Thanks Tom for the direction.
 
If you lose or have a poor ground for the battery, the voltage will become unregulated and toast any bulb that is "on". If the headlights toasted, the rear running light(s) probably also were lost. Gar Williams
 
tribouboys said:
The cut out was replaced at the same time the harness was replaced. The cutout I bought was from Mac's# A10505F. I think I will replace the cutout again on your suggestion but with a diode version. Any comments on the diode cutout??? Thanks Tom for the direction.
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I always use original cutouts, but if you go with a diode, then A&L makes the best I've seen. I'm not sure which dealers sell the A&L diode cutout, but you can ask them or call A&L to buy direct. 1-860-693-0112
 
What would the cutout have to do with bulbs burning out?? The cut out ONLY disconnects the generator from the battery at low speeds and at idle. The third brush adjusts the output. Check your wireing and switch, sounds like misconnections. G.M.
 
G.M. said:
What would the cutout have to do with bulbs burning out?? The cut out ONLY disconnects the generator from the battery at low speeds and at idle. The third brush adjusts the output. Check your wireing and switch, sounds like misconnections. G.M.
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If the cutout contacts are burned then the generator output can go very high. With the high output what would happen if the contacts suddenly made better contact with the lights on?
 
TinCup said:
Burn out or shorted out? Original sockets or sealed beam?
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Just more background. I replaced the wiring in the car. I replaced the harness, new head light sockets ,bulbs etc. I installed new batery cables. Everything is new reproduction. Since I knew I needed a good ground I took a grinder and lightly touched where the new ground cable is installed to ensure a good ground. I really felt I was being thorough when I replaced the wires. Since I installed a new cut out at the same time I felt I was in good shape. Since the cut out was sticking maybe I need to go back and look at all connections to ensure I don't have a short somewhere.
As I stated before when I shut the car off the amp meter would discharge but I would just hit the starter button the the amp meter would go right back to zero again.
I appreciate everyones comments to help get me in the right direction.
 
I would replace the cutout with a better one and take a voltage reading on it's output terminal (that's where the horn/lights wire connects). It should be battery voltage with the engine and light off. Start the engine and at fast idle the voltage should be a couple tenths of a volt more than battery voltage with the lights off. With the lights on the voltage will drop a little depending on how high the adjustable brush charge rate is set.
 
Ok I'm really discouraged at this point because I replaced the cutout with an old old I took off the car. When I shut the car off the needle goes right back to zero the way it should. I adjusted the 3rd brush back so the needle was at a very small discharge at idle I turned the headlights on and boom.... One head light blew and then I switched to high beam and back again. Eventually both lights blew out. Where should I start to research the problem?? New harness throughout the car. new bulbs sockets etc.
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Bob C How would I do that

Paul the harness is brand new. I have heard the repop sockets are not great. Could the issue be in the connection to the headlight where the wires plug in to the headlight.
 
When mine did this, I found a short in the connector at the base of the headlight bucket. They are now hard wired.
 
Mine was a total mis-match. One side of the connector was for a 2-wire connector, the other was for a 3-wire connector. It was a wonder that they ever worked at all. When I hard wired it, I ran an extra wire for ground as well. Haven't had a lick of a problem since then.
 
I had the same problem and it turned out to be the connections at the headlight sockets. But then later on a would blow the left headlight after about 1-2 weeks, not driving but maybe an hour or two per week at night. Come to find out I had a cracked battery clamp, and the cable would work it self loose and blow the headlight. Replaced the cable and no problems since, been 5 years!!
 
The answer to the problem of the blown bulbs is in this little story I wrote some years ago.
Rainmaker Ron
Curb service
Problems that can be solved using few tools and lots of logic.​
“Overcharged”
​
It was a beautiful fall afternoon. Ernie was tinkering around the back room of the station on not much of anything. He was mostly putting tools away from the last project and thinking of what to do next when the phone interrupted his daydreaming.

“Hi Ernie, this is Dan Lenhart from over in Hazelton,” announced the voice on the other end of the line.

“How are you Dan,” asked Ernie, “we haven’t heard from you for awhile.” (Dan bought quite a few parts from Ernie a few years ago when he first “resurrected” his coupe from the family farm.)

“I was hoping you could help me with something,” Dan said, “ Lately, when I start the Model A, the ammeter just stays about in the middle until I rev the engine and then it goes way over to the charge side. Actually it pegs the meter. Do you think my cutout is going bad or should I just send you my generator so you can test it?

“Lets take it a step at a time,” Ernie said, “The cutout is just a switch, its official description is a potential relay. When the generator voltage is greater than battery voltage, the cutout closes, effectively connecting the generator to the battery. When the generator output voltage falls below battery voltage, the switch opens to prevent the battery from discharging through the generator. The most common failure of the cutout is to “stick” closed, but we will get back to that in a moment. Are you having a problem with the cutout sticking and running the battery down?”

“I don’t think so,” Dan said, “ besides, I have a total disconnect on the car and I always shut that off when I am done using the car.”

“OK,” Ernie said, “ lets say the cutout is working. The next most common cause of the high charge rate you describe is a bad connection somewhere between the generator and the battery. A good way to understand what is happening here is to remember that the generator is only one component of the charging system and each component must function correctly for the system to work. The generator uses the battery as a reference and as a sink to control voltage in the system. A bad connection anywhere along the way will cause the generator voltage to spike to around 40 volts! The most likely place to find a poor connection is at the ammeter itself. Tighten both the inner and outer nuts on the terminals. Also check the connections in the terminal box on the firewall.”

“You mentioned a total disconnect,” Ernie offered, “can you describe it to me?”

“Yes,” said Dan, “it is one of those green knob things from Harbor Freight.”

“I see,” said Ernie, “either bypass it to see if your problem goes away or let the car run a short time and feel the knob to see if it is warm to the touch. Anytime a connection feels warm to the touch it is likely a bad connection.

“You also mentioned bringing me the generator to have it checked out.” Ernie said, “ You can save yourself a 40 mile trip by checking it on the car. With the engine shut off and the belt loosened, jumper around the cutout and the generator should motor in the direction of normal rotation. Lifting the third brush while in this test mode will cause the generator to speed up. If you generator performs as described, chances are it is OK.”


“I mentioned getting back to the sticky cutout,” Ernie said, “So many times mechanics, or should we say would be mechanics, focus on the symptoms instead of the underlying problem. When a component fails we need to look for a reason. In the case of most stuck cutouts the problem began with a loose connection. A loose connection in the charging system could destroy several components and yet be overlooked by the mechanic replacing the failed parts. Typically a loose connection in the charging circuit could; stick the cutout, burn the points, melt the coil, smoke the ammeter, fry the generator, cook some wires and blow any bulbs that happen to be on at the time. Combinations of the above are common. Mechanics that tackle the symptoms without finding and fixing the problem are also common!”
 
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