1936 Ford - Wiring Stock Gauges for 12 volt - Questions???

[DirtyDan]

I am wrapping up the build of my 36 5w coupe and I am trying to get my stock gauges to work w/ 12 volt power. For reference, I am running a 1952 8RT Truck motor with a Powergen 75 amp alternator. I am using a modern blade type wiring harness made by Haywire.

Ammeter:
I am going to assume I cannot use this since I am running a much higher amperage alternator and it will just peg my 30 amp gauge?

Fuel gauge:
I wired the gauge w/ the Runtz on the top terminal and the sending unit wire on the bottom terminal. I grounded the Runtz to the stud on the dash for the gauge nut. My gauge will not move from E. I have pulled the sending unit and checked the ohms and they change as I move the float up and down, but the gauge still does not move. I am getting 12v of power to the Runtz and it shows 6volt at the opposing terminal.

It seems as if my gauge is broken... Is there a procedure to test?

Oil Pressure Gauge:
I have installed the Runtz on the top terminal and have run the sending unit wire to the bottom terminal on the gauge. I am using the stock sending unit from the 1952 motor. I get no movement at the gauge. I have tried the sending unit from my original 36 motor and it will not take a reading either (this sender interferes w/ my throttle pedal linkage also).

What sending unit do I need to use to run the stock oil pressure gauge while running a 1952 motor? Is the oil pressure higher w/ these motors? My gauge only reads to 50 lbs.

Thanks in advance!

Dan

[COE Dan]

Dirty Dan,

I am using stock gauges in my 47 COE with 12V negative grounded power on a 59A flathead. They work correctly and I am using the Runtz voltage regulators across each guage.

First, did you convert your 36 from 6V neg ground to 12V positive ground? If so, you may have your circuits backwards.

Second, see my attached schematic - top half (bottom half is a separate circuit). This is how I hooked up the power to the gauges. The wire to the sensors on each gauge is the stock method.

Ammeter: Your new 75A alternator will not be pushing 75A to the circuits. Voltage throughout the system will always be 12V but accessories only draw as much power as they need. (i.e. a 1 amp bulb will only draw about 1 amp). So, you can use your old ammeter. If you ever draw 75A or see a full scale deflection you probably have a short. Also, 12V accessories take half the amperage to do the same work so you may not notice dramatic changes to your ammeter readings. I'm using the stock ammeter but I am running a 12V generator which has much lower output than your alternator. I've had no issues.

Fuel gauge: My fuel gauge is not connected. The original tank has been removed and an aftermarket tank installed. The original sender will not install in the new tank but the new tank has a sight gauge installed and I don't need the original.

Temp gauge: Works fine using stock sensors.

Oil Pressure gauge: My oil pressure gauge is the 80lb type. If you use the 80lb gauge, you need to use the 80lb sender. Likewise for the 50lb gauge/sender. They sender and gauges will work with each other but the readings will be off. However, all you really need to know on these flatheads is if you have pressure or not.

Last thing...it is possible you have two bad gauges...

Hope this helps.

COE Dan

[deuce lover]

Call Lee Kelley in Idaho.206-734-7785 and he is reasonable.He converted my 36 Oil & fuel guages to 12V and I am using the orig 50 lb oil sender & Drake fuel sender.He has done 3 cars for me and all were perfect.I wasted my money on the runtz and threw them away.

[Wingfield]

Ground the terminal from the fuel sender, your gauge should rise.

[Kurt in NJ]

If you ground the terminal to see if the gauge is working you need to be quick ,have someone watch ,just touch it for a second, too long and and it will burm out the gauge.

[DirtyDan]

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Thanks for the tips. I grounded the sending unit wire and the gauge did nothing. Looks like I need to find a new gauge or send them off to the gentleman in Idaho who rebuilds them.

[41ford1]

Do a resistance check across each gauge. You should get about 60 ohms. If they show open they are burnt out.

[Matt in Alameda]

I vote for Lee Kelly also. (See above post for phone#) He not only set my gauges up for 12 volt( in my 1935 5 Window) he replaced the glass tube gauges in my temp and gas gauge with LEDs....he then calibrated them. Modern and accurate and look stock. Matt in Alameda

[YBlockHead]

They correct phone number for Lee is 208-734-7785. The are code on the number above is incorrect.

[36tbird]

I think the safe procedure to check your fuel gauge is using a 1.5 volt battery. Those gauges are very ez to melt down. Look in there and you can see the little coil wire that is as fine a spider hair and therefore will not carry much amperage. And, unfortunately, they are hard to find replacements for. I ran my stock '36 gauges on 12 volts with drops and everything worked well. The amp gauge just acts like a wig/wag letting you know there is charge or not. I used a flathead oil pressure sending unit, again, not worrying about its exact reading, just letting me know that I had oil pressure. I used the temp bulb but had a direct reading gauge on the engine and over time learned the correlation between the two.

[rickmass]

My 1934 pickup is a 6 volt,some one put 12 volt gauges they are not wired,do they make or sale 6 volt gauges.Thank,s Rick

[Brian]

Mate, you've got your wires back arseward! I just checked under the dash of my car; the runtz connects to the bottom terminal of both fuel and oil pressure gauges. Use a 50 lb sender unit with your 36 gauge to get correct reading, using an 80 lb sender will work, but register a lower than actual reading. The ammeter will be ok on 12 jolts, however, as you'll be going neg ground you'll need to run the wire through the loop the opposite way. I assure you, this information is correct, I've run my 35 [with 36 fuel gauge]for years with 12 volts and runtz. Brian

[deuce lover]

I think he's figured it out by now.Original ad was placed over a year ago.