MTFCA Forum

I have installed a Rajo head on my T. I am trying an 8 volt battery to give the rebuilt starter a boost. It works great but now the headlights are burning out. I am using 6-8 volts bulbs . Is there an alternative 8 volt lamp or a LED lamp that will work on 8 volts ? Is there a resistor that will only drop 2 volts so the 6 volt lamps will work ?

Can't help with a solution to your problem other than to say that 4 of my 5 T's run 8 volt battery's for many years and rallies. I have never blown a bulb yet.

I did find a loose wire on the back of the head light switch. Maybe that contributed to the problem. I put in a new bulb and it instantly burned out. Burned bulb number 3. Checked the voltage at the lamp socket. 8 volts.

This place might be able to help you find what you need: https://www.ledlight.com/

A poor connection anywhere between the battery and key switch will allow the full unregulated voltage of the generator thru the lights if they are on. If the circuit to the battery is opened with the engine running at speed and lights on, the lights will instantly go super bright and burn out in about 1 second. If the circuit is intermittent like an open that occurs for an instant on an occasional basis, it could just burn out one bulb.

Even with an overhead or higher compression the starter should have no problem briskly turning the engine over. If it doesn’t, then the starter requires repair.

Adam D. is correct in both instances; the unregulated output of the generator can go as high as 10-12 volts and a "properly rebuilt" Model T starter will have no trouble turning over a Rajo equipped engine.
The problem with Voltage is people who do not understand electricity thinks more voltage is better and that is not always true.

I think the loose wire at the switch was possibly the problem. The engine was running at the time I tested the lights. I installed the new starter and the battery at the same time so a 8 volt battery was not really needed . The old engine and starter combination turned over fine . The new engine with the Rajo and old starter was very slow and hard to start.
I then went with a new starter and the 8 volt battery. The starter doesn’t slam into the ring Geer but turns over strong. The motor fires right off now.

If you have all new wiring, and a good clean starter switch, a six volt battery will spin that engine over like a champ!

Everything is new. Dismantled the car and started over. I had the dash apart to look for a gas leak (26 car) and probably caused the loose headlight and amp wire to be loose. Before I install any new lamps I will test the voltage with the engine running and see if the voltage goes up to 10 or 12 volts. Thanks, all the input has helped a lot.

The generator voltage will only go to the higher rates I mentioned above when the battery is disconnected and the generators goes into its "runaway" unregulated mode. A loose charging circuit wire on the switch or ammeter would case this.