I am looking at the wiring diagram, figuring out where to drop to 7.3 volts for the radio and gages. Is there a reason to not disconnect the wire from the solenoid that runs to the ammeter and run 7.3 volts to that spot? Looks to be the yellow wire in the print. It looks like that would put 7.3 volts to everything in the cab. Then I could run what ever I wanted off of 12 volts through a relay and a 12 volt fuse panel. Such as the headlights, I could hookup a relay to activate using 7.3 volts for the high and low beams and run 14 volts through the power contacts. I am adding turn signals and halogen tail lights so I would just wire those up to 12 volts.

 

would that also be in your charging circut as well?
not sure but I think my 48 was like that
I put every thing 12 v

 

The charging circuit would be 12 volts, I would have a voltage divider supplying 7.2 volts to the cab.

 

I think the amp guage only measures current flow. I don't think 12 volts will hurt it but I am not sure. The trucks built in the 70s used a shunt wire so that the amp guage wouldn't get the full flow.

 

I was looking at that point because it is easy to get to. I am going to put the voltage divider in the old 6 volt regulator box. The truck would look like it has two voltage regulators which most people probably won't notice.

 

Do you have a source for six volt relays? I want to do some relay tricks when I rewire my 48 but have not been able to find rrelays.

 

You just need a voltage drop resistor (one for each) in series with your fuel, temp, and oil gauges. The ammeter will be fine, as it inductively sense current direction. Unless it indicates backwards, then you will need to change the direction the wire passes the gauge. The resistors are available at auto part stores, restoration parts suppliers and ebay. I have had good luck on ebay with Autorewire; they sell the gauge resistors for $3 (Auction #
7966018392). For your heater fan and your electric wipers (if so equipped), you will need a 1 or 1.5 Ohm resistor, which will cost about $12. Autorewire sells them too. Everything else runs on 12 Volts, so you will need to replace all of your lamps.

Ford used 6 Volt gauges until sometime in the late 1970's.

 

www.digikey.com P/N JR1AF-DC6V. It is rated for 16 amps. A single 55 watt headlamp on high beam is 4.58 amps @ 12 volts. So I should be able to run both headlamps off of the same relay.

 

Thanks for the info and new bookmark.

Craig