How to convert 6v dash gauges to 12v...anyone know how?

[tokyo]

i got complete 50 merc dash at hershey, last night i was playing around with it (hitting the start button billy...BLUMP blummp, blump), cleaning it up and got to wondering how do these gauges get coverted to 12v. is there a simple process? or does it require expensive parts..curious to know how. Anyone got any ideas.

[Tuck]

?
tokyo...
dude, i have 12v's in my shoebox now with the same guages... they work both ways.. the bulbs are the things you have to change

[just steve]

Just did 12-volt conversion on my 54 Chevy pickup . . . any mechanical gauges (temp, oil press) don't need conversion.

Amp gauge needs nothing -- it don't care if it's 6 or 12 volts.

Gas gauge, electric temp gauge, or electric oil pressure gauge will EACH need a voltage reducer.

Two kinds of reducers work well for this:

Runtz Resistor -- usually has a tab with a hole that goes onto the gauge's power terminal. The power wire then connects to the other end of the Runtz, and there's a ground wire for the Runtz too. That's what I used.

6-volt Zener Diode -- goes in-line in the power feed to the gauge; not completely sure how these work, but they reduce voltage by 6 volts.

There are also big ceramic-looking voltage drops, but word is they're not as reliable or consistent. DOn't know for sure myself though.

later,
Steve.

[Petejoe]

Great article on this. I just used a resister for my gas gauge on my 37.Every other gauge worked well on 12 volts. Yes, even the electric oil pressure gauge. 12 to 6 volt conversion (http://www.oldengine.org/unfaq/six12.htm)
more good stuff also electrical related odds and ends (http://www.oldengine.org/unfaq/oddbits.htm)

[Missing Link]

tokyo,
probably the easiest way to go, if rewiring, is to use the Runtz resistors available from Speedway. Since the dash is out of the car they would be cake to install. The mount on the power side of the gauge and drop the 12volts down to 6volts so the gauge reads properly.

Of course the gauge itself could be bad in which case it is a waste of time anyway. http://www.jalopyjournal.com/ubbthreads/images/graemlins/smirk.gif but they are easy enough to test.

[tokyo]

the bulbs...of course...that is what else i was thinking about. The gauges should be fine...the stock ones look pretty shot though..might do something else with it then..

[SwitchBlade327]

how do ya test the fuel gauge? I need to do this before i get a reducer thingy.

[tokyo]

i am not sure on that switch...

[SwitchBlade327]

I figured link would look again, he's the one that said it was easy enough....I don't wanna rewire the shit if It still ain't gonna work, is there some kinda voltage drop you can just go get at napa? I know some 70's(?) cars had them on some of their gauges right?

[shoebox72]

I've done 12 volt conversions with & without a drop for the guages. The only difference I found is that the fuel guage will read about a 1/8 of a tank higher without a drop than with a drop. Yes, I ran out of gas. I used standard ignition P/N VRC603.It's a cluster voltage drop for 57 & later fords as they still used 6 volt guages into the 70's. You only need one and it goes into the wire that supplys power to the guages.

It's stupid to put one in for each guage because they all get power from the same 1 wire. got it?

Hope this helps. Billy

[Missing Link]

Yep, I'm real slow today. If you want to test the fuel sender, disconnect the power and place an ohmmeter on it and slowly move the float. If the ohm meter reading varies then the sender is good. To check the gauge basically do the same thing with the ohm meter. There is nothing to "move" to make the reading variable. And right now I can't remember which way the ohm meter reads with the sender float in the full position....hmmmm, dammit. Anyway, load the sender as if the tank was full and record your observation. Then check the gauge reading, is it at empty or at full when you look at the gauge without the car running? Remember that. Go post to post on the gauge and check for a reading. If you can get a reading of anything other than infinity at the gauge and the sender works, you should be in good shape. Did this help or complicate matters even more? http://www.jalopyjournal.com/ubbthreads/images/graemlins/wink.gif

[Petejoe]

Great link on electrical diagnosis
fuel gauge problems (http://www.mgcars.org.uk/MG_Elec-Tech/fuel1.html)