I have a forty ford that I recently changed the motor to a 49 cadillac motor with a twelve volt generator. I also installed a ron francis wiring voltage reducer so I could run the original gauges. The gauges worked fine when it was stock six volt but now I cant get any of them to work. I have checked the reducer and it is putting out six volts like it is suppose to. The reducer only had three wires red twelve volt, black ground and yellow six volt. I have tried everything I can think of and still cant get the gauges to work. Any help would be greatly appreciated i'm at the end of my rope I dont know what else to try.
To make this work right, use Ford gauges, Ford senders and a Ford cluster voltage regulator also known as an instrument voltage regulator (preferrably a 1959, B9A, unit since it has spade connections). Ford used the same King Seeley gauge all through the 6 volt era and 12 volt era through 1985(except 1956) and when they went to 12 volt after 1956, they used a cluster voltage regulator that give out a pulsed 6 volt signal to the gauges. The King Seeley gauges work on heat deflection and not as magnetic gauges work today. I have used many later model Ford gauges in 6 volt applications in my 50 years of turning wrenches by changing the face and needle to the 6 volt gauge and have never had a problem, the gauges only need the needle to have the same direction of sweep. Remember, gauges and senders MUST match and have no more than 6 volts supplied. Ford gauges do not have and polarity issues since it is driven by heat resistance rather that polarity. When you heat a coil to deflect a needle, it doesn't care it the power comes in pos. or neg. as long as the coil heats. If you have any more questions on how to make this set up work PM me and we can go over it.
temp and fuel should be the only electric gauges. The pos ground isn't an issue, I have my '47 hooked up with nos gauges and 12v neg ground. You need to have a runtz reducer for EACH gauge you want to use. The reducer goes on the + side, the sending unit on the other and then run a ground wire from the gauge housing to a good ground.
For others who read this thread, voltage reducers (Runtz and many others) are based on a $0.50 integrated circuit. Head over to the tech section to learn how to make your own for about three dollars each. Also, old gauges are electromechanical, so polarity (negative or positive ground) doesn't matter. The key, as mentioned above, is to keep the gauge and sending unit a matched pair.
Thanks for all the help. I'm using original 40 ford sending units but still won't work. I tried taking the supply wire off the switch n running the 6 volt wire from the reducer to it n still nothing. I tried hooking the 6 volt reducer wire to different gauges n still nothing. Still lost as to where the proper hook up is
I have original gauges on my 40 Ford running on a 12V system. Hook up 6V to one post on the gauge and the sender to the other post. You can use one 6V reducer for the oil, water and fuel gauges - that's how Ford did it when they went 12V. If you short the sender post to ground (don't do it for long), the needle will peg high. If it doesn't then you either don't have power or the gauge is burnt out. You didn't hook them up to straight 12V did you? You can dis***emble the gauges fairly easily and see if both wires to the bi-metal strip are still good or you can use a multimeter to make sure you have continuity between the posts. If you think the gauges are bad, go get a cluster from a newer Ford and swap them out. I bought a 59 Ford cluster with regulator for $7 but anything up to 79 or so will work. Note that the 40 gauges have a unique needle. They can be swapped with some patience. Please send them to me before you throw them out. If you have doubts about the senders, get some for say a 75 Ford F150. They will drive the gauges just fine and are very cheap. Make sure to get senders for gauges and not idiot lights. The Batt gauge doesn't play well with the regulator. I hooked mine up to 12V with a resistor in line to get it to read right - might have been 54Ohms or something in that neighborhood.
If none of the gauges are working, my su****ion is that you have a bad ground at the dash. Nothing should have changed for your fuel gauge, so if it was working before but isn't working now it has nothing to do with the engine swap. Red goes to a switched 12v source (ignition), yellow goes to the gauge, and black to a good ground on the dash. Also be sure you have a good connection with your grounding strap from the engine to the firewall and/or ch***is. Contacts should be clean and bright for best results.
The 40 Ford gauges are not grounded, as previously stated they are King Seeley bi-metallic thermally actuated gauges modulated by points type King Seeley senders. If you have known good, correct, senders (they have a high failure rate) and an appropriate voltage drop to the gauges then the only logical conclusion is that the gauges were overheated at some point and have lost continuity. You should have a volt gauge in that cluster if I recall, what did you do to adjust it to the 12 volt system? PS: the battery gauge should actually be grounded via the half insulator and an over-sized washer, just to correct my blanket statement.
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