1955 12V Alternator conversion GEN light on

J

Jeff55

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1955
My GEN light stays on as soon as the battery is connected. The car was converted to 12v neg ground some years before I got it.
I changed over to an alternator using the kit from CASCO. When I reconnect the battery, the GEN light stays on. I have not tried to start it yet.

Any ideas?

Jeff
 

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Jeff55 said:
My GEN light stays on as soon as the battery is connected. The car was converted to 12v neg ground some years before I got it.
I changed over to an alternator using the kit from CASCO. When I reconnect the battery, the GEN light stays on. I have not tried to start it yet.

Any ideas?

Jeff
Click to expand...
You may want to check your wiring to the alternator. The light should not come on until the alternator "excites" the dash light.
 
When you connect the battery is the key on? If the key is on then the light should be on. If the key is not on I don't see how it will power one side of the light. So if it does you will need to dive into how someone wired your alternator.
 
The key is not on. Not even in the ignition switch. Otherwise, I would expect the light to come.
 
Just a couple of questions. Is the alternator a one wire version that only has a hot wire hooked up to it. Is this alternator an internally regulated unit, or does it have a separate voltage regulator? Single wire alternators will not operate the dash light. The type of alternator you purchased will determine the wiring for the generator light.
 
It is a single wire, internally regulated alternator.
I have attached the instructions.
 

Attachments

  • alternator kit.pdf
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As per your instructions that's the way my system is wired. I have a 56 but even though it comes from the factory as a 12volt the wiring to the generator is same. Make sure you are using a good isolation system to the gen light and the wire from your alternator. I'm guessing that you have voltage on the gen terminal and that shouldn't be. If you measure any voltage on the junction then that will reverse feed the gen light back through maybe the points or some other path to ground.
 
Jeff, please post the solution once it's sorted out. I converted my 55 to 12v. No problems with generator light, but I'm considering replacing the 12v generator with an alternator.
 
Jeff55 said:
My GEN light stays on as soon as the battery is connected. The car was converted to 12v neg ground some years before I got it.
I changed over to an alternator using the kit from CASCO. When I reconnect the battery, the GEN light stays on. I have not tried to start it yet.

Any ideas?

Jeff
Click to expand...
 
This is just a scientific wild-ass guess (SWAG) theory. I have the original Electrical Equipment Installation Manual 55, 56, 57 But I can't determine if this bulb has a diode. The DC current is now flowing in reverse. A diode prevents back-flow of DC current. If there is a diode in the circuit, reverse it. Check with an electrical guy before cutting it apart to install one. It will need to be sized correctly and installed in the correct direction.
 
Jeff.. Did you use the FIBER INSULATING BLOCK as shown in the instructions and on the photo? If not that is probably your problem.
 
4VE said:
This is just a scientific wild-ass guess (SWAG) theory. I have the original Electrical Equipment Installation Manual 55, 56, 57 But I can't determine if this bulb has a diode. The DC current is now flowing in reverse. A diode prevents back-flow of DC current. If there is a diode in the circuit, reverse it. Check with an electrical guy before cutting it apart to install one. It will need to be sized correctly and installed in the correct direction.
Click to expand...
No diode in the original generator charging system. When the key is turned on power is sent from the ign switch to the light. the other wire runs from the light, through the voltage regulator and grounds through the non-running generator. When the engine starts and the generator starts producing voltage then that voltage is sent up to the gen light. When the light sees power on both sides (ie no ground) it goes out.
 
jimntempe said:
Jeff.. Did you use the FIBER INSULATING BLOCK as shown in the instructions and on the photo? If not that is probably your problem.
Click to expand...
I did use the insulated fiber block. I verified that it was not conducting to the terminal on the voltage regulator.
 
Jeff55 said:
I did use the insulated fiber block. I verified that it was not conducting to the terminal on the voltage regulator.
Click to expand...

If I read the diagram right it should be like the attached pic
gen light wire.jpg
 
Last edited by a moderator:
jimntempe said:
If I read the diagram right it should be like the attached
Click to expand...
That is what I have. The snap on plug attaching the warning light wire (using the old field wire) to the alternator seems a bit flimsy. I will verify that connection.
 
You bought the car converted to 12v Neg ground correct? If you have a volt meter disconnect the black wire from the indicator light on the alt. Now connect the battery and see if there is 12v at the terminal on the new alt. If so there is a fault in the alt. If there is no voltage at the terminal then ground the black old field wire. If the light comes on with the ign off and the field grounded, then there is a wiring issue with the car.
 
Critterpainer said:
You bought the car converted to 12v Neg ground correct? If you have a volt meter disconnect the black wire from the indicator light on the alt. Now connect the battery and see if there is 12v at the terminal on the new alt. If so there is a fault in the alt. If there is no voltage at the terminal then ground the black old field wire. If the light comes on with the ign off and the field grounded, then there is a wiring issue with the car.
Click to expand...
Yes, the car is 12v neg ground.
There is 0.15 volts at the 'warning light' connector on the alternator when the battery is connected.
When the connector is plugged into the alternator there is 0.15v at the fiber insulator end of the old field wire. (plug is good)
Since the old field wire has a minute voltage should I still try the grounding part?
 
yes ground the wire coming from the bulb. Just want to make sure the light stays off with the Ign off and comes on when the key is turned on. Less than .15v should not be enough to light that bulb.
 
Critterpainer said:
yes ground the wire coming from the bulb. Just want to make sure the light stays off with the Ign off and comes on when the key is turned on. Less than .15v should not be enough to light that bulb.
Click to expand...
It will be a while before I can get under the dash to find and ground that wire.
 
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