Stovebolt.com
Posted By: 38_1.5Ton Original gauges.. can I use a 12 volt bulb? - Tue Jul 20 2021 04:33 AM
Hi All,
Using the original speedometer and gauges, can I use a 12v bulb for lighting? OR MUST it be a 6 volt bulb? I am getting into an area of little expertise. :/ Thinking out loud, I put a 292 in it.. let's see:

A. Theres the water temp gauge.. I dont think that uses electric.. just a metal or copper wire to the engine? (right pic)
B. Oil pressure.. I am not sure if the uses electric.. just a metal or copper wire going to the engine.. I guess a sensor on the 292 connects to that? (left pic)
C. Gas gauge, I guess the sending unit in the tank (12v) but there are 2 insulated electric wires on the back of the gas gauge - electric but not exactly sure what for.. (right pic)
D. AMP gauge has two bolts and studs on it.. but not sure how that hooks up.. (left pic)
E. I *thought* 12v bulbs work with 12v system.. or am I missing something in regards to the gauge housing?

Attached picture ampoil.jpg
Attached picture gasWater.jpg
As long as the bases have the proper offset of the locking lugs and the proper number/position of the contacts, the bases don’t care what voltage bulb is in place. The bulbs are only for lighting the gauge for night driving nothing else. The 6 volt wiring is plenty heavy enough to handle the much lighter 12 volts. Read the Stovebolt Tech Tip on 12 volt conversion to ease your mind about what your doing.
Posted By: buoymaker Re: Original gauges.. can I use a 12 volt bulb? - Tue Jul 20 2021 02:12 PM
A. Capillary tube filled with gas. Handle very carefully. Crimp or crack the line and you'll have to buy a new one. The bulb at the end may require an adapter to fit your 292.

B. Mechanical. Your 292 may have an electrical sensor on the block, remove it and install the line. Adapter may be needed.

C. A sore subject that typically leads to catfights on this forum. I recommended replacing the gauge for one that is made for 12 volts and your stock 30 ohm tank level sensor. If you connect 12 volts directly to your stock 6 volt gauge, it will smoke it.

D. Amp gauge doesn't care if it is 6 volts or 12 volts. Use the same wires.

E. Read previous post.
Posted By: 38_1.5Ton Re: Original gauges.. can I use a 12 volt bulb? - Tue Jul 20 2021 03:16 PM
Thanks guys! thumbs_up I will also review the 12volt conversion page. I didnt see that.

"A. Capillary tube filled with gas. Handle very carefully. Crimp or crack the line and you'll have to buy a new one. The bulb at the end may require an adapter to fit your 292." <-- that is cut. I will have to find another line.. not sure where but will look. Bulb.. hmm, did not know there was one on that water temp gauge.. just thought there were two connected to the speedo, will relook. headscratch

B. Line is cut on that too.. will need another. and look for adapter!
Posted By: buoymaker Re: Original gauges.. can I use a 12 volt bulb? - Tue Jul 20 2021 04:04 PM
Since you are going with a 292 engine, save yourself a lot of trouble trying to restore the old gauges. You can buy modern looking gauges that will mount below the dash. You have a 292 engine that can use the more modern electrical sensors (water and oil). You can get them at your local parts store. The one to be careful with is the fuel gauge. The fuel level sensor in the tank has a 0 to 30 ohms range of operation.
Posted By: 38_1.5Ton Re: Original gauges.. can I use a 12 volt bulb? - Tue Jul 20 2021 06:59 PM
Well I would consider that. But I would want gauges that fit into the existing holes. Dunno if anyone makes them.
Posted By: buoymaker Re: Original gauges.. can I use a 12 volt bulb? - Tue Jul 20 2021 10:26 PM
Past conversation to restore 1953 temp gauge.
https://www.stovebolt.com/ubbthreads/ubbthreads.php/ubb/showflat/Number/1224340

Once you have the gauge working, you will need a device to drop the voltage from 12 volts to 6 volts.

Attached picture is to show what a complete gauge looks like.

Attached picture Temp Gauge.jpg
Posted By: bartamos Re: Original gauges.. can I use a 12 volt bulb? - Tue Jul 20 2021 10:57 PM
1. You have a 12V battery, yes?
2. Are you in the process of converting to 12V?
3. Are you adding a new harness?
4. Your 292 is a 12V motor, yes? Came with 12V starter, generator, voltage regulator, coil, yes?
5. Foot start? or electric solenoid?
6. Do you have a ballast resistor?
7. Are you doing turn signals?
8. What year is your 292?

I think you need to wait and be careful until you explain what is going on. All we know is you are asking about bulbs. Ammeter and fuel Sender are not voltage dependent.
You say: I *thought* 12v bulbs work with 12v system.. or am I missing something in regards to the gauge housing?

You also ask if you should use 6V or 12V bulbs. If you are indeed converting to 12V, there are a whole lot of things to know. If you use gauges, electric heater fan motor, bulbs, coil, generator, voltage regulator..... that are from a 6V system, in a 12V conversion, you will burn things out!!!!!!!!!!!!

We can advise every step of the way to a conversion. One step at a time.

You are in "interiors" this should be in electrical.
Posted By: 38_1.5Ton Re: Original gauges.. can I use a 12 volt bulb? - Wed Jul 21 2021 02:41 AM
Understandable. We dont have time to be experts on everything or even know what to ask at our first time around, yes I will gladly entertain your questions. smile For starters, I was worried about blowing up the gauges somehow by using 12v bulbs without a reducer. I now know the gauges can be separate from the bulb current.

More, I have ripped out any and all wiring from this 83 yr old truck. Converting to twelve volt with totally new harness/alternator etc..and would like to use original gauges for originality. Learning as I go.

1. Do you have a 6V or 12V battery? yes 12v, I have to do that to use 12v bulbs I believe
2. Are you in the process of converting to 12V? yes
3. What are you doing? See 1 and 2 (I think)
4. What motor do you have? What year motor. In original post 292ci, '84 but converting to one wire system (just learned what that was)
5. Foot start? No, I am going key start.

I think you need to wait and be careful until you explain what is going on. All we know is you are asking about bulbs. Senders are not voltage dependent.
You say: I *thought* 12v bulbs work with 12v system.. or am I missing something in regards to the gauge housing?

You also ask if you should use 6V or 12V bulbs. If you are indeed converting to 12V, there are a whole lot of things to know. If you use gauges, electric motors, bulbs, coil..... that are from a 6V system, in a 12V conversion, you will burn them out!!!!!!!!!!!!
I agree totally. I was worried about blowing up the gauges somehow by using 12v bulbs without a reducer.

More learning:
The AMP gauge brings AMPS INTO your cabin, and I learned some folks tie it into ignition. I have also heard this blowing out everything on a bad day and truck not starting.. I dont think I like that..
The oil gauge is mechanical and literally directly connected to the oil.. as an oil filled line. I dont think I like that.
The water temp gauge is mechanical, it is also similar to the others. I can see my self keeping the gauges, maybe using the water temp and oil pressure.. but getting a separate Volt gauge.

After learning all of this, I am also looking into modern gauges that fit right into the original dash holes for the '38...
Posted By: bartamos Re: Original gauges.. can I use a 12 volt bulb? - Wed Jul 21 2021 03:31 AM
Sounds good.
1. If you have a points distributor you need a ballast resistor or equivalent for a 12V system.
2. Mechanical gauges are just fine if you can find the correct "sender" to fit the 84 motor.
3. ALL bulbs need to be 12V
4. The only gauge that needs a reducer is the gas gauge. Gauge is separate from bulbs. One of the terminal on back of gauge is for ignition switch power. The other is for the sender wire. Don't get them crossed. The one from ignition switch gets the reducer. American Classic trucks sells them for $6.
5. Good idea to abandon the ammeter and install volt meter.
6. I prefer the " 3 wire" alternator hook up. Which is really only two wires. One more than a one wire.
It's all up to you as far as how modern you want to get. Good luck.
Posted By: 38_1.5Ton Re: Original gauges.. can I use a 12 volt bulb? - Thu Jul 22 2021 04:14 AM
Well, heres what the water gauge looks like.. and no it does not read temps! (as you can see) FAncy looking mechanism here.. wink wonder what is busted and what can be fixed.. I see no 'bulb' in it (myself). headscratch Any ideas? Oh and I am out of gas!

Attached picture IMG_5227.jpg
Attached picture IMG_5228.jpg
Attached picture IMG_5229.jpg
Attached picture IMG_5230.jpg
Posted By: buoymaker Re: Original gauges.. can I use a 12 volt bulb? - Thu Jul 22 2021 07:53 PM
Back-up! I'm confused.

The picture on the left is an example water temperature gauge with all the parts that make it operate.
Notice a bulb-shaped sensor attached to the end of the tube.
This sensor goes inside the engine block or head and makes contact with the engine coolant.
This is a mechanical gauge. No electricity required.

The picture on the right is a typical 6 volt bulb that shines light into the gauge cluster.

Which bulb are you talking about? I need to get this straight (understood) before we can continue.

Attached picture Which One.jpg
Posted By: 38_1.5Ton Re: Original gauges.. can I use a 12 volt bulb? - Thu Jul 22 2021 07:58 PM
Ohhhh well now this is making sense to me. I dont have that left pic bulb or it is on the engine somewhere! So I need to find that, if it is on the original engine and reattach ? (or get a new one) I *thought* a tiny 'bulb' similar to the one on the right was inside the mechanism (my mos right pic) Now that you have explained that, I understand. So - no it is not a light buld or even like a lightbulb I need.. it is a mechanical 'bulb'. Yes.
Posted By: buoymaker Re: Original gauges.. can I use a 12 volt bulb? - Thu Jul 22 2021 09:32 PM
I could not find a New Old Stock gauge. Unfortunately I could not find a reproduction gauge like the ones for 1947-55 Chevy trucks.

Used gauge.
https://www.ebay.com/itm/114673227986

This is a rebuilt GMC gauge from Jim Carter who is well know at Stovebolt. Your broken gauge may require an additional $60 core charge. Call them for details.
https://oldchevytrucks.com/resp275.html
Posted By: 38_1.5Ton Re: Original gauges.. can I use a 12 volt bulb? - Thu Jul 22 2021 09:36 PM
Okay. Thanks very much buoymaker!
Posted By: buoymaker Re: Original gauges.. can I use a 12 volt bulb? - Thu Jul 22 2021 10:10 PM
You also have other options:

* Cut a big hole in your dash for a modern $200+ instrumentation panel and buy individual modern gauges to fit the holes. This is the least favorable solution with the Stovebolt members.
* Buy a new reproduction 1949-53 Chevy truck gauge with white needle and try to swap the gauge faces. Can be difficult.
* Buy a new low cost mechanical water temperature gauge and use the parts to fix your broken gauge. This can be very difficult to do.

Personally I would worry more about fixing/restoring the more important parts of your truck first then deal with the gauges later.
You can go to a local parts store and buy lower cost gauges and use them as a temporary solution.
I reused my temporary gauges on a homemade engine stand.
© The Stovebolt Forums