Graham Man

12V Dwell meter on 6V?

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Anybody know if you can use a 12v dwell meter on a 6v car?  I was thinking you could just use a 12V power supply on the meter?

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No reason not to. One of those little booster battery packs would be handy. Have you tried it on 6V?  It might work, mine does.

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Posted (edited)

Probably not in many cases. Try your 12v meter. If it is a two-wire meter there is a fighting chance it might work, even on 6v positive ground (with the leads reversed for positive ground).

 

If it is a three wire one, I don't think you will ever get it working on 6v positive ground and would likely damage it trying. On 6v negative ground maybe? Try it!

 

All it has to do is swing to 0 degrees with the points closed, and the number of degrees between cylinders with the points open. If you can get it to do this you are home free.

 

For instance, an 8 with a "normal" ignition system fires every 45 distributor degrees, a six every 60 degrees, a four every 90 degrees, and so on.

 

Some dwell meters have "set" marks at the high end of the dwell scales and a "calibrate" knob. That probably increases your chance of success.

 

Edited by Bloo (see edit history)

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Tell us the brand name and model, that will help to determine if it might work.  Pic too if you can.

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Posted (edited)

Found this online

 

There is a simple way to get the 12 volt meter to work on the 6 volt ignition system. It requires a battery from a motorcycle, dry cell from a light, whatever has 12 volts. 

Connect the power wires from the tach/dwell to the 12 volt battery, then, add a ground wire from the 12 volt battery to the engine, and connect the sensor wire form the meter to the negative post on the coil. read dwell/rpms, set accordingly.

The power supply from the 12 volt battery will NOT interface/interfere with the 6 volt system. The ground wire from the 12 volt battery to the engine proper only completes the READ circuit on the meter, the two different voltage systems remain separated.

Dwell meter/tach reads correctly when connected in this method.

Edited by Detroit_Electric (see edit history)
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1 hour ago, Detroit_Electric said:

Found this online

 

There is a simple way to get the 12 volt meter to work on the 6 volt ignition system. It requires a battery from a motorcycle, dry cell from a light, whatever has 12 volts. 

Connect the power wires from the tach/dwell to the 12 volt battery, then, add a ground wire from the 12 volt battery to the engine, and connect the sensor wire form the meter to the negative post on the coil. read dwell/rpms, set accordingly.

The power supply from the 12 volt battery will NOT interface/interfere with the 6 volt system. The ground wire from the 12 volt battery to the engine proper only completes the READ circuit on the meter, the two different voltage systems remain separated.

Dwell meter/tach reads correctly when connected in this method.

 

Yup, I did this in the distant past - it works

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Posted (edited)
3 hours ago, Graham Man said:

I assume they made 6V models?

 

Yeah, I restored one. They do seem to be a bit hard to come by, but some 12v models should work.

 

3 hours ago, Graham Man said:

This one says for 6 or 12V

 

Yeah, note the 2-wire hookup. That dramatically increases the chance it will work on positive ground, but you would have to check the book for sure.

 

3 hours ago, Detroit_Electric said:

Found this online

 

There is a simple way to get the 12 volt meter to work on the 6 volt ignition system. It requires a battery from a motorcycle, dry cell from a light, whatever has 12 volts. 

Connect the power wires from the tach/dwell to the 12 volt battery, then, add a ground wire from the 12 volt battery to the engine, and connect the sensor wire form the meter to the negative post on the coil. read dwell/rpms, set accordingly.

The power supply from the 12 volt battery will NOT interface/interfere with the 6 volt system. The ground wire from the 12 volt battery to the engine proper only completes the READ circuit on the meter, the two different voltage systems remain separated.

Dwell meter/tach reads correctly when connected in this method.

 

Yeah, that should usually work. I do that with timing lights.

 

One should check that it is swinging the needle far enough. In that scenario, the electronics inside the meter have the 12v supply they need, but the wire from the coil is swinging from 0-6v instead of 0-12v. If the needle goes to zero with the points closed, and the correct number of degrees with the points open, its fine. I wouldn't trust it without checking it first though.

 

Also, if you tried to do this on a positive ground car, it couldn't really work. Although the meter would have the 12v it needs to operate, the wire from the coil would be swinging from 0 to negative 6 volts, and in the wrong direction. There would be 18 volts between the wire from the coil and the 12v supply wire. The meter was probably not designed to deal with 18 volts between those wires, and would probably be damaged. If by some miracle it worked, the needle would swing the wrong way and try to go off the scale. If you could center it up on the scale somehow, the numbers on the scale would be backwards.

 

If you are going to gamble, something with 2 wires is a much better bet, because you can just hook it up backwards on a positive ground car. Even better if it actually says it does 6 volts.

 

 

Edited by Bloo (see edit history)

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If it swings the needle in the wrong direction how about reversing the wires connected to the meter?

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Posted (edited)

That works on 2 wire meters as long as there is enough swing. On 3 wire meters there is more than likely going to be smoke.

 

Edited by Bloo (see edit history)

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What I was suggesting was actually taking the meter apart and reversing the leads that are connected to the meter movement if it pegs the needle backwards not the leads coming out of the meter. 

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On 8/24/2019 at 7:47 PM, Larry Schramm said:

I use a 12 volt battery for the power supply and everything works fine on the one I have.

 

This method also works for a timing light....... ;) 

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