The Stovebolt Site Forums The Shop Area The Electrical Bay 37 1/2 fuse block questions

By no means am I a expert on 12v wiring. How many circuts and what needs needs to be fused on my resto. Nothing extra on my truck except a heater. Converting to 12 v except for heater and putting voltage reducer on that. Any and all help appreciated. Bill

Bill
The originals had only one 30 amp fuse housed in a holder on the back of the ammeter, as I recall. Are you replacing all the wiring with a new wiring kit? I think I and most here would recommend so doing since 82 year old wiring likely has been subjected to who knows what kind of wear and tear. The Shop Manual shows the wiring diagram. I think one is also shown in files available on the “Old Car Manuals” website.

I added electric wipers and turn signals to my ‘37 that a previous owner converted to 12 volt. For each of those additions I included inline fuses. Recollection is fuzzy now, but I think they are 10 amp? I also added a battery cut off switch I use whenever the truck is not being used, which can be months at a time. I know some of this is redundant and likely unnecessary but, stories of shop fires etc make the precautions worth the effort IMO.

Lee, yes new wiring harness is being installed. Converting to 12 v. After further reading and though will fuse each circuit. Never thought about a disconnect until you mentioned it, so will install that also. I was planning on using the original light switch which does have a fuse holder on it and also horn is also wired off of the switch. So will fuse horn separately. I have a new 6 position fuse block and was hoping that would cover everything. Any thoughts on that? Also see there is lots of info on the tech tips. Thanks again for you help. Bill

Is the preference to have a fuse on each circuit? If so, six may or may not be enough.

12 volt heater motors are readily available rather than running a resistor, etc.

Ed

Ed, my heater is in great shape and works great and has been pressure tested. The motor is soldered or welded into the radiator portion of the heater and hate to mess with it. Do you happen to know how many amps heaters pull? I'm sure it is not much as the feed wire is #14 or 16. Thanks for your reply. Bill

For your heater, I would suggest a 1 ohm 50 watt resistor. That is what I used on my 51 when I converted to 12 volts. The truck part vendors sell them.

It is quite common for the original fuse holder to give some trouble. Often times there is some heat buildup in the holder itself and it keeps blowing fuses. One common solution is to solder in a new fuse holder. That is what someone did on my 38 Master and it works fine.

Bill, volts times amps equal watts, so using above resistor(50w) says 4 amps. I always use larger wire, wire is cheap, eliminates problems down the road. Most wires in a 6 volt truck are already large enough for 12 volts.

Ed

Thanks for everyone's input!!

Nominally you would want 6 volts across the resistor and six volts across the fan motor. However the system will charge somewhere around 14.5 volts. So if you had around 7 volts across the resistor and the motor was drawing 6 amps, you would be dissipating 42 watts through the resistor. So I would fuse it around 10 to 15 amps and a size 14 wire would do the trick.

Thanks Truckernix