Hot Rods Identify this part please?

Can anyone tell me what this part is? It is under the dash on my newly acquired 1947 Chevy fleetmaster. I am thinking it is some kind of resistor for the 6 volt gauges to work with 12 volts(though none of the gauges work). The white material is like that white material on an ignition ballast resistor.
Thank you

 

Yes! We called them ****on resistors back in the day. I used one of them on my '32 (avatar) for the 6V heater motor. Works like a champ and I put it in line with a 3-speed switch.

A lot cheaper and easier than trying to find a replacement 12V motor. Got it at one of those old NAPA stores where they still had parts catalogs that someone knew how to use! LOL

 

that is a voltage reducer but probably won't work for gages. napa sells those and they come with instructions on how to figure out the load and how many to put in series.

 

The only gauge in a 47 fleetmaster that might want the correct battery voltage is the gas gauge. The others probably are not connected, if they don't work...

 

How many original 69 year old gauges are gonna work anyways regardless of voltage, get some new ones that will work.

 

I have a bunch of 50-60 year old gauges that still work.

 

Thank you for the replies. Maybe it is for the dash lights. I don't know if they are the original 6 volt bulbs or not. I believe the blower motor is from a 70's Camaro (12 volt).

 

It appears that the voltage reducer is being used for the gas gauge, but the gas gauge is not working. The voltage going into the voltage reducer is 11.8 volts and coming out is 11 volts. Shouldn't this be reduced down to 6 volts? Is there an adjustment on the reducer or does it just reduce 12 volts to 6 volts? If the reducer is not reducing down to 6 volts, could that be the reason the gas gauge is not working? Thank you

 

Putting 11V in to a 6V gauge can't be good for it.

 

You need a runtz resistor for the fuel gauge...Get at Speedway and maybe Summit, E bay too..Not cheap, around $15.00...If you are using pos grd where original was neg grd you have to swap the wires on the gauge follow Runtz instructions [I think, pretty sure]..

 

it needed to have a few of those in series to work with the small load of a fuel gage. if the guy who wired it had read the instructions he would have known.
the runtz resisters work well. but the gage is probably bad now that it ran with that much voltage.

 

The part is also called a ballast resistor. I had a '55 Ford converted to 12 volts and used one to reduce voltage to the radio.

 

shouldn't that voltage reducer have reduced it down to 6 volts?

 

Cheap way to reduce the voltage to you gauges, is head to the wrecking yard and pull the little reducer off the back of a speedometer on the 60's through 70's Ford and Dodge (maybe all Mopars?) as they still had 6 volt gauges, one reducer runs all the gauges.

I've only used those big ceramic reducers for motors -heater and wipers- if I recall they still allow around 9 volts through.

 

it could if it had something that was a larger load. it has to do with ohms and someone will give an explanation that we won't totally understand. use it for your heater motor and it will work fine.

 

If you guys think the original gauge is shot now, can I buy an aftermarket 12 volt 0-30 ohm gas gauge and mount it under the dash?

 

Did you measure the resistance of the sending unit? The sender wire, disconnected from the gauge, and measured relative to ground, should show somewhere between 0 and 30 ohms, depending on how much gas you have.

 

I did not measure the resistance. So I need to see what the resistance is from the wire coming from the sending unit to the gauge is, correct ? Disconnect the wire from the gauge, use the ohm meter on that wire then to ground to measure the resistance?

 

yes, measure the resistance between the gauge wire, and ground. If it's infinite (open circuit), then the sender is bad, or the wire is broke somewhere, or the sender is not grounded at the tank. If it reads between zero and 30 ohms, then there's something wrong with the gauge itself, or the power to it.

In my limited experience, the old 6v GM gauges will actually work with 12v going to them, but they don't really like it. The preferred method to drop the voltage is with a voltage regulator, such as an LM7806. (it's a little electronic part that looks like a transistor, has 3 leads, the input goes to the 12v source, one goes to ground, the other is the 6v output to the gauge)

 

I measure around 13 ohms between the wire from the sending unit to ground. So I believe the sending unit is good and is grounded therefore either the gauge is no good or not working correctly because it is getting too may volts. I will now be looking to make a LM7806 regulator or look at the bone yard for a reducer from an older vehicle.

 

They never used them in older vehicles. GM did not have voltage reducers. Ford and Dodge vehicles had voltage reducers, but they use a different kind of gauge, if you try to use one of those reducers on a GM it wil just make the gauge jerk back and forth.

The LM7806 is an electronic part, you can get it from electronic parts places, such as DigiKey, Mouser, etc.

 

I've determined the gas gauge is bad. I fed it with 6 volts from my battery charger and the needle did not move at all and it stayed on empty. Do they sell an aftermarket under the dash 12 volt 0-30 ohm gas gauge?

 

Did you measure how much voltage a 6v battery charger puts out, when it's not connected to a battery?


but yeah, nowadays you can buy anything!

http://www.summitracing.com/parts/atm-2517/overview/


.

 

Jim, the charger puts out 6.6 volts when set to 6 volts. Thanks for your help.

 

that's good. You never know....some of the older ones don't have much regulation.

you're welcome!

 

Not going to help if the gas gage is no good, but I use the LM7806 for the gas gage in my 37 Chevy Ute and it works great. So in case anyone sees this thread, and doing a 12v conversion, get the LM7806's, they are good for about 1 amp which works good for a gage application. Not good for heater or wiper motor, just low power stuff.

BTW - You can buy them real cheap on ebay shipped from China if you wait 1-2 weeks for arrival.

 

The 7806 is essentially turning 6v in to heat, so be careful of how and where you mount it and connect it to the wiring harness.

 

The LM7806 has a mounting tab, it's a good idea to mount it to metal, with a screw. Attaching it to metal will give it all the cooling it needs. The tab is also a ground connection, so if you do this, you don't really need to run a separate wire to the ground pin.