Electrical Gremlin

[Ridermike]

Hello all, I need help with an electrical gremlin that’s driving me crazy. I have a 42 WLA composed of several bits and pieces of new and old. This bike sat in a dealer’s show room for 15 years (unstarted) before I got my greasy hands on it and one of the first items on the way to road worthiness was a new wiring harness. What a rats nest, wire nuts, tape, you name it. I bought a new harness from 45 parts restoration and all seem well until I started it. Here is the problem. I am running a model 61 generator with an original Electric Franks regulator. I’m sure I have the regulator hooked up right (it charges well); my gremlin is in the GEN light. When the wire from the GEN light to the A terminal is hooked up, all seems to work fine until I turn the IGN switch off; the bike keeps running and the GEN light comes on very dim. With the wire unhooked the switch works fine.
Any ideas?

[Perry Ruiter]

The trick with wiring one side of the bulb to the A terminal is to give it a path to ground when the generator's output is less than the battery voltage (the other side of the bulb is connected to the battery). So when the engine is off and the switch is on current flows from the battery through the bulb and the generator to ground and the bulb is illuminated. Of course when the engine is running and the generator is producing the wire attached to the A terminal is at generator voltage. Now both sides of the bulb are at the same voltage, there is no path to ground and the bulb is off. When you turn the switch off with the engine running the path is reversed and voltage goes from the generator through the bulb, through the coil and to ground. The bulb is dimly illuminated and the coil gets just enough to keep the engine sputtering along.

So, you can either put a diode in line between the bulb and the A terminal (a diode only lets current travel in one direction so you can't have it reversing when you turn the switch off). Or, you can pick a bulb with enough resistance that there's not enough current passing through it to power the coil. You say it's a WLA but a mix of parts. What kind of dash base do you have on the bike? A stock catseye base? In that case your generator bulb would typically be a #63. Try switching that out for a #67 bulb which is the 12 volt version. Obviously the bulb will be much dimmer when the switch is on and the engine isn't running but it should allow the switch to actually kill the bike. The simplest solution is probably not to change anything and just choke the bike when you turn it off. That should kill it ... Perry

[flat-happy]

hello ridermike---welcome to the forum. perry knows his stuff. im up in gallatin tennesssee. do you know jerry crain in pegram? electrics frank's old bikes are really close to here. he made a great product. very smart man

[Ridermike]

Perry, thanks for the information, it should really help me out. Let me ask you this, if I install a diode in line, will my GEN light still work? I understand that a diode will let the current travel in one direction but will it still let the light go to ground in the event of generator failure or even when the engine is not running. Yes I’m using a stock dash so I could do the #67 bulb. I asked about instructions for the Electric Frank’s on another forum and e-mailed the outfit that is reproducing them now; all they say is, Green to Field, Black to Batt, and Red to Arm (Gen Light). I wonder how Frank handled this problem.

Hey Flat, glad to met you. I just know Jerry from Boswells. I didn’t know he lived in Pegram. Small world. You’ve probably seen this bike I’m working on. It sat on C&S’s show room turn-table for 15 years.

[Perry Ruiter]

Perry, thanks for the information, it should really help me out. Let me ask you this, if I install a diode in line, will my GEN light still work? I understand that a diode will let the current travel in one direction but will it still let the light go to ground in the event of generator failure or even when the engine is not running. Yes I’m using a stock dash so I could do the #67 bulb. I asked about instructions for the Electric Frank’s on another forum and e-mailed the outfit that is reproducing them now; all they say is, Green to Field, Black to Batt, and Red to Arm (Gen Light). I wonder how Frank handled this problem.

Yes, as long as you install the diode the right way around it will allow the light to work and stop the run on. Install it the wrong way round and the light won't work and it won't fix the problem. I doubt back in Electric Frank's heyday anyone much cared about idiot lights and none of the three wires have anything to do with one. The field connection is used by the regulator to control generator output. The arm connection is the generator output to the regulator and the battery connection is regulated output to the battery. The primary purpose of the A terminal is generator output. The fact that an idiot light can be hooked up and work is just a happy coincidence of the fact there is a path to ground through the positive brush, armature and finally negative brush and that path doesn't exist when the generator is functioning.

70165-78 is the diode Harley used on the later Sportsters for this purpose. Google implies it's still a good number if you want to pay Harley $10 for $1 part ... Perry

[Ridermike]

Thanks again Perry. I’ve got a friend getting the diode for me for free.

[Ridermike]

I installed the diode yesterday and all works fine.
Thanks Perry