12 volt fuel gauge

[jgreg53]

Is there a way to make a 12 volt fuel gauge work on these 6 volt systems?

[Sniper]

Not simply

[Plymouthy Adams]

depends on the era of the vehicle, who made the vehicle when the industry first went to 12 volts, the ignition systems and most gauges were not changed and their movement  and electrical requirement stayed the same but the now 12 volts driving them were reduced by the application of the CVR which is a constant voltage regulator.  Dropping resistors for coils.  By this time the ole mopar two wire was long gone and so retrofitting to this is not that much a deal.  Lose the CVR given the donor is using this.  Match the gauge and components operation requirement, sender/gauge.   You can mix and match makes and models given you work with the requirements of each.  Today in the little Brit car I am building, it uses the CVR and stock fuel gage and its sender in 20-220 and looking about I installed an older Jeep tank (new repop 15 gallon verse factory 6.inadequate) and modified the mounting base and added third generation Dakota ceramic sender.  Only thing I was not happy with was not finding a ceramic compatible resistor block with low fuel circuit for that reminder light we all like today.  The modern devices has ohm ranges into the 1Kplus these days.

Edited October 5, 2023 by Plymouthy Adams

[Sniper]

I did assume an aftermarket 12v gauge

[Plymouthy Adams]

I hear you Sniper and I may well be in error to assume retrofit and my response as correct may be wrong for his application.....I did not assume aftermarket as that is generally offered with its own sender and most follow the SW system requirements.   Being a 'blender' of this and that, I assumed and probably wrongly, he was mixing old with newer.

[jgreg53]

Yes it is aftermarket.  I have a couple of converters I am trying.not sure of the connecting pattern. It has an in side and an out side.

[Plymouthy Adams]

then I would suspect that the operational parameters are set by the aftermarket maker/supplier and is best answered by them.  

[D35 Torpedo]

So you want a 12 volt gauge to work with a 6 volt sender?

[maok]

The sender is not 6 volts, its just a variable resistor.

 

Just buy a 6volt to 12volt converter then use this to feed 12volts to your gauge. These are readily available on ebay, very cheap too.

 

However, the sender resistance range may or most likely, not match your gauge requirement. Do you have the specs of the gauge ie its resistance range?

[jgreg53]

I have a couple of six to twelve volt converters.  Not entirely sure how to wire them in. They have in and out leads.  Do the in leads wire between the switch and the gauge? If so where do the out leads connect?

[Sniper]

Not sure how well a 12v negative ground converter will work being fed by a 6v positive ground system when the sender uses the chassis ground as a path?

 

I'm think smoke will be released.

Edited October 6, 2023 by Sniper
I really need a new keyboard

[jgreg53]

I think you're right.  The gauge that just stopped working is a nos unit that I ordered from ebay. It worked for a while.  When it stopped working I thought it was a calibration problem. I removed the sending unit and wired it directly to the gauge and it did nothing. I don't think the blades were heating up. I think some of these nos parts lose their shelf life on the shelf. The thin wires on the gauge grow brittle over time. Then what you ordered is a 70 year old part.

 

[Sniper]

Wait you have the thermostatic fuel gauge a different animal than my 51's.

 

[jgreg53]

Yep 

[jgreg53]

I'm familiar with how it's supposed to work.  If it's working right,  you can actually see the bi metal blades bending and sometimes smell the coils heating up.

Edited October 7, 2023 by jgreg53

[jgreg53]

So I took the faceplate off the nos fuel gauge. I sprayed the whole thing really well with contact cleaner. I attached the 3 wires without the face plate and the needle moved. The only thing I can think is the faceplate was bent back just far enough to keep the mechanism from working. Put it all back together and it works.