Roger W Gerow
Senior Member
Can anyone recomment a reliable company to convert my 1940 Ford instruments from 6 volt to 12 volt. Have researched the voltage reducers, now looking into the coversion side. Thanks
Converting Instrument Voltage
- Thread starter Roger W Gerow
- Start date
paul2748
Well-known member
williamson's. www.williamsons.com Why don't you use the Ford instrument voltage reducer?
deuce lover
Well-known member
Lee Kelley in Idaho.Reasonable and good work.His email(leebobk@cableone.net)
Henry/Kokomo
Well-known member
Williamsons X 2
19Fordy
Well-known member
(How I did mine using stock wiring harness.) I am not an electrical whiz kid so use at your own discretion.) It worked for me. The stock BAT guage on my car is a voltmeter. Thanks to "Flat Ernie" for all his help. Sorry, but if I rotate the Instruction Sheet the type gets smaller. So tilt your head 90 degrees. I hope this helps. It's a lot cheaper than sending your gauges out for conversion. The 60 ohm fuse cost 40 cents.
How To Make Stock 1940 FORD DeLuxe Guages Work When Converting From 6V to 12 V.
1.DISCONNECT BATTERY CABLES FIRST.
2.Install a Constant Voltage Reducer (CVR) and fuse block on your inner firewall.
A. Remove brass strap between oil and battery gauge.
B. Also disconnect green/black wire that supplies power to gauges at BAT Gauge.
C.Cap or tape off wire terminal on end of green/black wire in B.
3. Connect a wire with a 60 ohm resistor to BAT terminal that had the brass strip on it to the 3 amp fuse on fuse block . This wire supplies power only to the BAT gauge and no other gauge. That is why you remove the stock brass strip. Do not reconnect the green/black power wire.
4.Connect a jumper wire between terminals on back of oil and fuel gauge as shown on sketch.
5.Disconnect green/black wire power wire from terminal on Temp gauge. Cap or tape it off as you won’t be using it.
6.Connect 6V. yellow wire from CVR to the terminal where the strap is on the Temp. gauge. That wire feeds only the Temp., Fuel and Oil gauges.
7.Connect red 12V wire fromCVR to 5 amp fuse on fuseblock. This wire supplies 12V to the CVR.
8.Connect wire with a 60 ohm resistor from the BAT terminal on the back of the gauge to the 3 amp fuse on the fuse block. This reduces the 12 V back down to 6 V.
9.Connect an 8 or 10 gage wire between the “coil” terminal on the back of the ignition switch and the input power supply terminal on the fuse block.
10. The 12V wire for the electric fuel pump that was attached to the “Coil” terminal on the back of the ignition switch is now connectd to the appropriate fuse at the fuse block.
Photo shows needle to be in the green after the implimentation of this plan.
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Roger W Gerow
Senior Member
Thanks everyone for your quick response.
Seth Swoboda
Well-known member
Use the voltage drop/regulator. Nothing personal but Williamsons will cost you your first born child.
Yes they were used in millions of ford cars and trucks and work excellent . I have used them myself many times and have not had any problems at all.
fortyfords
Senior Member
A 64 ford mustang instrument voltage regulator is small and uses the flag type terminals and is available at the auto parts store, very easy to install and mount. But the batt gauge is a volt meter so you must put a variable resistor in series with the gauge, adjust the resistor till the gauge needle reads at the top of the first red bar. Take the variable resistor out and read the resistance and then install a fixed resistor of that value and install in series with the voltmeter. I did this on my forty and it worked for me for many years. The gauge needle will be in the green when going down the road and in the yellow band with the lights on and in the red band when the alt. isn't working. The top red band is when the alt. is overcharging. Good luck
41ford1
Well-known member
A suggestion for dealing with the voltmeter. Measure the resistance across the terminals of the meter. Then put a resistor of equal value in series to the ground lead. A resistor with a rating of 5 watts or higher should be OK.
My set up was done with Runtz voltage reducers. They were originaly mis-wired so the regulator chip was fried. I had to replace all of them with a 7806 regulator chip. These are basically the the same as what 19fordy did. If I was to do it again I would go his route. Much less expensive than the Runtz. If you use Runtz be sure to connect the ground lead.
My set up was done with Runtz voltage reducers. They were originaly mis-wired so the regulator chip was fried. I had to replace all of them with a 7806 regulator chip. These are basically the the same as what 19fordy did. If I was to do it again I would go his route. Much less expensive than the Runtz. If you use Runtz be sure to connect the ground lead.
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Flat Ernie
Senior Member
It always amuses me how many opinions there are on this topic. 
Simplest & cheapest is the 7806 chip - they're cheap, maybe $0.15 each. One for each gauge except your voltmeter. Put a 60 ohm resistor (precision wire wound) in series with it - it's close enough.
The runtz are resistors and aren't as stable as the digital CVRs. The 'factory' 56-9?? Ford item is a chopper and while it will work, also isn't stable. Like many things, there is more than one way to skin a cat and your opinion of what is 'better' is just that...an opinion. It boils down to what you value most...cost, simplicity, accuracy, ease of installation, or???
Simplest & cheapest is the 7806 chip - they're cheap, maybe $0.15 each. One for each gauge except your voltmeter. Put a 60 ohm resistor (precision wire wound) in series with it - it's close enough.
The runtz are resistors and aren't as stable as the digital CVRs. The 'factory' 56-9?? Ford item is a chopper and while it will work, also isn't stable. Like many things, there is more than one way to skin a cat and your opinion of what is 'better' is just that...an opinion. It boils down to what you value most...cost, simplicity, accuracy, ease of installation, or???
Ron Knowles
New member
I found that on my 40 Ford, putting the runtz voltage reducers in when rewiring, the gauges were not steady and accurate. I got a CVR and installed. Now gauges work as advertised.
rotorwrench
Well-known member
The old instrument voltage regulators as used in the early 12-volt Fords up into the 60s are chopper units. They do not provide a constant voltage as some folks might have been told. They work on the same principle as the old King Seeley pressure and temperature gauges that Ford used by opening and closing points rapidly to control the output voltage. An old needle swing volt meter will be all over the place when you read the output voltage. These things didn't work all that well when they were new. The indicator needles tend to wiggle around a lot.
The modern 6-volt constant voltage regulators are what they say and function well with the King Seeley gauges. They work better if each gauge has it's own unit and they are not that difficult to set up.
The large CVR with the heat sink marketed by some is rated at 1.5 amp so it should work on the King Seeley systems. They have to be hard wired to the gauges plus a ground for the CVR. These things are sensitive and can be damaged when folks are troubleshooting systems so care has to be taken during that process. They warn folks about that in the instructions.
The process of converting gauges is basically remove old 6 volt guts and install 12-volt guts. The sending units have to be matched up for them to function properly. This can be an advantage but it can also create other problems at times. A person needs to make a note of the part numbers of affected parts in case they need to look for new parts at some point. Some replacement parts are just as hard to find as old original items after 20-years or so. Nothing lasts forever.
The modern 6-volt constant voltage regulators are what they say and function well with the King Seeley gauges. They work better if each gauge has it's own unit and they are not that difficult to set up.
The large CVR with the heat sink marketed by some is rated at 1.5 amp so it should work on the King Seeley systems. They have to be hard wired to the gauges plus a ground for the CVR. These things are sensitive and can be damaged when folks are troubleshooting systems so care has to be taken during that process. They warn folks about that in the instructions.
The process of converting gauges is basically remove old 6 volt guts and install 12-volt guts. The sending units have to be matched up for them to function properly. This can be an advantage but it can also create other problems at times. A person needs to make a note of the part numbers of affected parts in case they need to look for new parts at some point. Some replacement parts are just as hard to find as old original items after 20-years or so. Nothing lasts forever.
