Fuel Gage - volatge senstive?

[MuskegonFlatheadFan]

I really don't want to scratch the 6v versus 12v scab, but here we go.
Does the fuel gage even care about volatge? It seems to me that it shouldn't. Both the sending unit and the gage are basically variable rehostats. I did the conversion on my 40 deluxe and need to do the dash next. I've read many posts about the conversion and using voltage reducers, it has me wondering.

[Flat Ernie]

Yes, it does.

They are not variable rheostats at all. They operate on the principle of differential heating. There are bi-metallic strips (a strip of metal with two different kinds of metal on each side bonded together that have different coefficients of expansion). When heated, they bend and when bent, produce a different tension required to move.

Pick up a Ford Service Bulletin - it explains the operation well.

Bottom Line: You need 6V to the gauge for it to operate properly. You can get close with a dropping resistor, but I'm of the opinion that the gauges work much, much better and far more accurately with a constant voltage regulator. The 7806 CVR produces 6V output with an input of 10-18V or thereabouts. This gives far more accurate gauge readings than even the stock 6V system because the voltage is steady and constant. You need one per gauge - although different CVR will have a higher output current and can run all three gauges - oil pressure, water temperature, and fuel gauge. These are cheap enough (<$.50/each) to run one for each gauge and keep a spare or two in the toolbox.

Your voltage gauge requires a dropping resistor of approximately 60 ohms. You need to use an accurate, precision, wire-wound resistor of exactly 60 ohms for this purpose. The el-cheapo radio shack carbon resistors are not nearly accurate enough to use for this and the precision resistor will only cost a few dollars at most. This will put your "green band" right at about 13.5-14V on your gauge.

[MuskegonFlatheadFan]

Do you have a good source for the 7806 cvr?

[Richard in Florida]

Originally Posted by Flat Ernie

You need one per gauge - although different CVR will have a higher output current and can run all three gauges - oil pressure, water temperature, and fuel gauge.

No, you don't need three. I've been running all three gauges in my '53 on one 7806 for years and it hardly even gets warm using a simple heat sink.

The photo shows two 7806 regulators; the second one was for a 6-volt tach I was using back then. It has since been disconnected.

[john worden]

I'm building a complete new 12 volt system in a 40 standard now. I bought the 12 volt conversion guide booklet from Drake. It is written by Fifth Ave Antique Auto Parts in Clay Center Kansas and is quite complete and thorough. They reccommend their "Runtz" voltage drop ( approx. $18 each ) for all the instruments but the volt guage. They reccommend having the volt guage converted to 12 volt which I am having done now at ADT Instruments Intl. Inc. in Bloomington Minn. They restored the complete cluster as well.

John

[51 MERC-CT]

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Originally Posted by MuskegonFlatheadFan

Do you have a good source for the 7806 cvr?

Use of a 7806 requires some fabrication and is available here----

http://www.ebay.com/sch/i.html?_nkw=...tage+regulator

as well as other places.

You can get a ready made regulator here.----

http://macsautoparts.com/early-v8-voltage-reducer-reduces-12-to-6-volt-v12871/camid/F30/cp/340RW35U1000017/

[Planojc]

Here is one from Vintage Auto Garage

[19Fordy]

This will also be helpful re: volt gauge conversion.
https://www.fordbarn.com/forum/showth...olt+conversion

[ic237]

Here is another one that wont break the bank, it does all your gauges, you only need one.

http://www.ebay.com/itm/271008367259...84.m1586.l2649

[Butch11443]

You can also use a stock one for a 57 to 59 Ford. They work great.
Butch

[Flat Ernie]

Originally Posted by Richard in Florida

No, you don't need three. I've been running all three gauges in my '53 on one 7806 for years and it hardly even gets warm using a simple heat sink.

Yes, you can get by with one, but you're running pretty close to max capacity for it. These things are super cheap, so the extra $.50 to get two more will hardly break the bank...A good heat sink, which it appears you have, helps a lot though.

Originally Posted by john worden

I bought the 12 volt conversion guide booklet from Drake. It is written by Fifth Ave Auto Parts in Clay Center Kansas and is quite complete and thorough. They reccommend their "Runtz" voltage drop ( approx. $18 each ) for all the instruments but the volt guage. They reccommend having the volt guage converted to 12 volt which I am having done now at ADT Instruments Intl. Inc. in Bloomington Minn. They restored the complete cluster as well.

The Runtz is expensive and is just a resistor. The voltage output varies with the voltage input and current through it. It is a poor choice for gauges, although they do work satisfactorily for most folks.

By "volt gauge", are you referring to the "Batt" gauge on a '40? If so, a precision 60-ohm resistor is all you need to "convert" it. No changes or alterations to the gauge itself.

Originally Posted by Butch11443

You can also use a stock one for a 57 to 59 Ford. They work great.

The factory (instrument reducer) IR is a chopper style. It works too, but again, is a poor choice for gauges, IMO. For original style gauges that used a chopper, it works fine. And will probably work satsifactorily for most folks too, but it's not the most accurate thing in the world and if you buy it new at NAPA (vs scrounging in a junk yard), they're expensive.

[deucemac]

A Ford B9MZ-10804-C or NAPA IR1 regulator works perfect and supplies a 6 volt pulsed signal to the gauges. It is a stock ford art for 1959 and I have used them many times with excellent results.

[BILL WZOREK]

Ok what is the "C" in CVR

C=?
V=Voltage
R=Reducer

a little slow this AM

THANKS

[51 MERC-CT]

Originally Posted by bill wzorek

ok what is the "c" in cvr

c=?
V=voltage
r=reducer

a little slow this am

Thanks

Constant
Voltage
Regulator

[Flat Ernie]

Originally Posted by deucemac

A Ford B9MZ-10804-C or NAPA IR1 regulator works perfect and supplies a 6 volt pulsed signal to the gauges. It is a stock ford art for 1959 and I have used them many times with excellent results.

Many people do use them with good success. However, it's a poor choice for gauges, despite being an OEM part (my opinion from an electrical/electronics perspective only - nothing more - take it for what it's worth (exactly what you paid for it)). The chopper or pulsed signal cannot provide the most accurate reading. Accurate enough? Probably. But they're $30 (unless you scrounge one in a junkyard) and the CVRs are pennies. New technology. Sometimes it is better.

[BILL WZOREK]

51 MERC-CT
Let's see I got one out of three correct thats 33 1/3 % Correct.
that's about the same test scores I got in High school. LOL LOL

THANKS
now if I can just remember where I file this it will be Ok.

[Derby]

I was unaware that the fuel gage and sending unit are bi-metal units. I would appreciate a more complete explanation of how they operate. Does the Drake sending unit use a bi--melal strip also?

[tubman]

Originally Posted by Derby

I was unaware that the fuel gage and sending unit are bi-metal units. I would appreciate a more complete explanation of how they operate. Does the Drake sending unit use a bi--melal strip also?

Check this out : https://forum.hetclub.org/uploads/Fi...de0f4d6d0a.pdf.

[19Fordy]

Originally Posted by Derby

I was unaware that the fuel gage and sending unit are bi-metal units. I would appreciate a more complete explanation of how they operate. Does the Drake sending unit use a bi--melal strip also?

Derby, here's a post that will answer your question. It tells how gauge and sending unit work on the bi-metallic principle. Scroll to #4.
https://www.fordbarn.com/forum/showt...k+sending+unit

[Derby]

Many thanks. Just what I needed!