I put a new repro gas gauge in my '39 Buick project. The seller (cars.com) says it will work with 6 or 12 volt. Do I have to put some sort of reducer, if so what should I get? Thanks
should work, but you coulld put in a solid state voltage regulator (LM7806) if it'll make you feel better
just install as is. the gauge is a variable resistor for the ground side of your dash gauge, if want to check it before you install it, plug it in to the wire to your gas tank, and ground the sending unit to the chassis. with key on move the float on the sending unit thru its sweep and watch the dash gauge. it should follow what you are doing, just a little slower.
I don't think you can run 12 volts on a 6 volt gauge. If your electrical system is 6 volts, which I assume it is, your should be OK. If it is 12 volts you will need a voltage reducer to the gauge.
"put in a solid state voltage regulator (LM7806) if it'll make you feel better"... Actually I was going to hook it up without any resister etc. and a friend questioned it, then somebody here said I'd get "catastrophic failure"....I don't understand why it wouldn't work. Thanks
Some gages are made to only work on 6 volts, but the GM fuel gages seem to work ok on either 6 or 12, they use two coils inside that work against each other. I assume you paid $$$ for the gage, if that's the case you probably ought to put in a voltage regulator. Note that a regulator is not exactly the same thing as a reducer/resistor! For a resistor to work right, it would need to be matched to the load. A solid state voltage regulator doesn't care what the load is (as long as it is less than the maximum rated current), the output voltage always stays at the rated voltage.
at an electronics store. Radio Shack stocks the 7805, which is a 5 volt version, and might work ok. it costs about a dollar and a half, so it woudl be worth experimenting with.
Went to Radio Shack, all I could get was an LM 7805. Can I use that and how would I hook it up? Thanks
it will probably work ok, give it a try. connect the 7805 input to the ignition switch, connect ground to the car's ground (this connection is also the metal tab, so you can probably just put it under a screw on the back of the gage cluster), connect the 7805 output to the gage's IGN terminal.
a NTE5118A zener diode will work to drop voltage. it drops 12 to 6 volts and they are rated at 5watts cost $2.50. zener diodes work the same as a solid state voltage regulator. last gas gauge project i worked on the local radio shack was out and all the people there were brain dead!
You can use any 6 volt gauge on a 12 volt system as long as the power wire to the gauges is fused. On my 51 Buick i use my old 6 volt amp & gas gauge. They are the only powered gauges. I have no issues at all. I can see how much gas I have in my car and I can also see that my batt is being charged. the only thing you need reducers for is your heater motors and you can use one on your stock horn if you still have it.
Ford and dodge both used voltage regulators on thier 12 volt systems for the gauges designed on 6volts way into the 90's. Infact most systems are regulated to lower voltage even currently. Remember more volts=less amps. Your just using the sender as a resistor to ground. It doen't care if it is 12, 8 or 4 volts, Hell your ohmmeter has a 9volt battery and some are a couple of1.5volts and workfine with less than .03 miliamps, when you use it to check the sender in the first place. The only gauge in a 6 volt system that can cause trouble is the amp gauge as it's shunt is only rate at 30 or so amps. Your 65 amp alternator will smoke it and cause a fire. Use a small jumper lead like 14 gauge and jumper across the terminals on the amp gauge to help share the load, to fix that problem.
be careful with trying to use a thermal regulator from a Ford or a Dodge instrument panel in a GM car, the gages work quite differently...it won't do what you want it to do.
Why is that. I have done it and had no problems. These cars have been running for years this way. Is there some other reason I should know. I am being serious not confrontational. I wire hotrods and customs as my own business and fix electrical problems all day everyday for a local shop in town. If there is a problem that will seriously cause some damage, I don't want to steer anyone or do it myself. Please explain.
The gages in the Fords and Dodges are thermal gages, not magnetic gages. The thermal regulators work by limiting the "average" voltage, they use an on-off switch on a bimetal strip. The GM gages are magnetic, they react instantly to changes in voltage, they don't move slowly like the ford/dodge gages. maybe you are using some type of modern electronic replacement regulator instead of the old bimetal thermal ones? it's been a while since I've bought one of the replacement regulators. or else you are using the thermal regulator and it is just staying on all the time (full 12v) because the magnetic gages don't draw enough curren to turn it off?
Good point. Yeah they are magnetic and they don't click or pusle like when used in a ford or dodge. Come to think of it, I think the new ones I have been using are not the bimetal ones for the fords either. I know I have them around and have used them. You must be correct about them stayin on. The mag ones don't get "hot" like the older ones did, so the bimetal regulator would just stay on. I never really looked at it that way. Thanks for the brain jog.
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