I changed to 12 volt
 

Hi All,
I recently changed to 12 volt on my 41 Ford Coupe. I now have a non working sending unit. My heat and cold gauge now when I shut the car off goes all the way to H when it is off. The charging gauge stays right in the middle when running . When I put the lights on it is discharging a little bit. Can anyone tell me what I did wrong. Me and the electrical parts on my antique cars never got along. Any and all help will be very much appreciated.
Thanks ,
Joe D

Re: I changed to 12 volt
 

To start with do you have a voltage reducer or reducers to the gages?

Re: I changed to 12 volt
 

Painless wiring has a module for the 6V instruments. Drops the 12 to 6V

Re: I changed to 12 volt
 

NAPA has a Voltage reducer part #vt6187, I believe these were used on late 50's Fords.Won't hurt to call!

Re: I changed to 12 volt
 

what kind of alt do you have? voltage reg? and yes the voltage reducers are a must

Re: I changed to 12 volt
 

If you didn't use a 12V to 6V resistor/reducer on all requiring 6v then you probably fried or damaged everything requiring 6v. You needed a 12 V coill & light bulbs, & any gauges or electric motors like your heater blower, using electric would need the voltage reducer You will be okay with the amp gauge if it's what you're calling your charging gauge as amps are amps 12V or 6V doesn't matter as long as you didn't change the wiring and run it thru the wrong direction. If so it will register backwards. if your starter is 6v no prob it can take the 12v and it will run twice as fast wich will start your engine great.

Re: I changed to 12 volt
 

I did my 50 f1, put a Runtz diode on all gauges, got them on epay and they come with instructions not hard to do, go on positive side of guage one for every guage, 10 to 12 bucks each

Re: I changed to 12 volt
 

You didn't say .... did you also change your system to negative ground ?

Re: I changed to 12 volt
 

Search 12v conversion on this site.

Re: I changed to 12 volt
 

The mistake was changing it to 12v.

Re: I changed to 12 volt
 

Joe,

I'd hate to even guess, based on the opening post. Without telling more about "what" you have done, and "how" you did it, everything else is just a guess.

I'd love to help you figure it out, but I would need to know more about the "what and how" of your 12v conversion.

Here's a page that I used, somewhat as a guide, when I did a total rewire of my '40 stake truck. http://www.oldengine.org/unfaq/six12.htm

Re: I changed to 12 volt
 

Joe, The first thing I did was install a CVR from Ron Francis. That allows the gauges to still operate on 6V. Then to make the BATT gauge function properly I isolated it from all the other gauges and installed a resistor in the 12V wire that feeds it so the 12V voltage would be reduced to 6V. In a 40 Ford the BATT gauge is a voltmeter, not an amp meter. Check out posting #6 here.
https://www.fordbarn.com/forum/showth...olt+conversion

Re: I changed to 12 volt
 

Call me crazy, but as far as I can see you haven't described anything wrong. Temp gauges are normally to the right on "H" when shut off, unlike a fuel gauge which goes to the left to "E".
The "charging gauge" ammeter should be in the middle when running and slight discharge with lights on.

Re: I changed to 12 volt
 

Nothing from the original poster after the first post!?

Re: I changed to 12 volt
 

That ammeter gauge has a "very slight" movement. But you will need a voltage reducer as advsed above.

Re: I changed to 12 volt
 

Ammeters don't get voltage reduction in any case.

Re: I changed to 12 volt
 

Fact! DD

Re: I changed to 12 volt
 

Ford gauges are operated by a heating element that surrounds a bimetal strip. If the voltage isn't reduced to six volts, the gauges will be destroyed in a short time. As said above, the '40 used a voltmeter, not an ammeter, so a series resistor must be used to place the needle in the green section. If the deflection of the gauge is large, place a voltmeter across the battery and watch the level under load, such as headlights, to see if the generator or alternator output is sufficient, and the regulator is working.