More light switch problems

Barry B./ Ma.

Barry B./ Ma.

Well-known member
When I started my 30 roadster to warm it up yesterday it started and ran fine but when I tested the lights they went out on high beam, the generator stopped charging and the fuse was blown. The parking light bulbs were blown along with the tail lights. It is a repro light switch but worked perfectly last year. I am considering bypassing that troublesome switch and installing a 3 poition pull type switch under the dash panel. For safety reasons I don't want to switch on or off high beams at night an have all the lights go out because of a blown fuse. I hate to have to fine tune that rotary switch again so wondering if others have the same problem. I could leave the switch in the low beam position but that's not ideal either. Very frustrating , this is the third repro switch since I restored the car. I wish they could come up with a good original type switch.
 
could the short be in the headlight pig tails / socket area??
i would ck there first at the end of the juice
 
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Could be in the pigtails, thanks Mitch, I forgot all about those, I've had to grind down the diameters of those on other Model A's. I don't remember doing these. Barry
 
Barry B./ Ma. said:
When I started my 30 roadster to warm it up yesterday it started and ran fine but when I tested the lights they went out on high beam, the generator stopped charging and the fuse was blown. The parking light bulbs were blown along with the tail lights. It is a repro light switch but worked perfectly last year. I am considering bypassing that troublesome switch and installing a 3 poition pull type switch under the dash panel. For safety reasons I don't want to switch on or off high beams at night an have all the lights go out because of a blown fuse. I hate to have to fine tune that rotary switch again so wondering if others have the same problem. I could leave the switch in the low beam position but that's not ideal either. Very frustrating , this is the third repro switch since I restored the car. I wish they could come up with a good original type switch.
Click to expand...

Barry, I think you will find your problem in the charging circuit, not the switch. Here is a little story I wrote as part of a series to help club members understand their cars. 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 com
 
Thanks Ron, I'll check the battery connections and the frame ground. It had been sitting all winter and the ammeter was around 12 amps when I tested the lights. Something happened when I switched to high beam and she stopped charging even with part throttle. I don't use one of those green knobs, instead I have a master switch in the negative line (going to the starter). Once I switched the light switch to off position, turned the master back on, started the engine the generator charged at 10 plus. The headlight bulbs never blew out probably because the filaments are stronger and I only ran it for a few seconds. Probably overcharged because the battery lost ground. Should I place the master switch on the ground side instead of the starter side?
 
So far after poking around with it today I've found gray corrosion on the battery ground post and connector. The ammeter and terminal box connections were good. I removed the battery and cleaned it up and the connections. The frame crossmember ground area was rusty so that will be cleaned up and coated with dialectric grease. I plan to run another ground cable from the frame to transmission, thanks Ron, I think you headed me in the right direction. I think the generator ran wild without the proper battery balance and new ground cables should rectify that. Now to do some clean up on the coupe. The coupe has an alternator and with an internal regulator it should be less of a problem in output regulation but I will clean up the connections anyway..
 
Barry B./ Ma. said:
So far after poking around with it today I've found gray corrosion on the battery ground post and connector. The ammeter and terminal box connections were good. I removed the battery and cleaned it up and the connections. The frame crossmember ground area was rusty so that will be cleaned up and coated with dialectric grease. I plan to run another ground cable from the frame to transmission, thanks Ron, I think you headed me in the right direction. I think the generator ran wild without the proper battery balance and new ground cables should rectify that. Now to do some clean up on the coupe. The coupe has an alternator and with an internal regulator it should be less of a problem in output regulation but I will clean up the connections anyway..
Click to expand...
Yep, we used the generator system for years, when they work as designed, no problem...when the "loop" is not complete the problem can show up anywhere or sometimes everywhere! Our job is to find the problem and not get sidetracked by the symptoms. Sounds like you are on the right track! Rainmaker Ron
 
Ive never had a problem with an original or repro light switch.What likely happened was a short in Hi beam circuit that blew the fuse & caused gen voltage to spike.It could also damage the gen.I use a 30 amp breaker at the starter & 20 amp fuses on head light circuits.
 
Good advice Columbia. I agree that the rotary switch is ok but I was suspicious as I had trouble before with the repros. I don't know yet what set this scenario off and it could be very well in the pigtails on high beam. I'm taking it a step at a time and I did find a fair amount of corrosion on the frame mount for ground. I cleaned everything up and applied a coating of dialectric grease and also added a heavy ground to the transmission. Got that all buttoned up and now will double check the headlights. When it occured the ammeter showed a 0 charge but as the ground was corroded and the fuse was blown it probably didn't register the run away voltage which blew out the small bulbs.
Thanks guys for all the help and suggestions. Barry B.
 
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