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TR2/3/3A Installing a Voltmeter on a TR3?

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K

karls59tr

Obi Wan
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Does anyone know of a link or info on how to wire up a Voltmeter to a TR3 that has been converted to Neg ground and has an Alternator? Can the Voltmeter be installed where the Ammeter is or can the Ammeter stay where it is and still function with the Voltmeter uner the dash?
 
Yes, you can have both. The volt meter power is picked up from the ignition switch and the other terminal is grounded. Illumination is simply tapping into the light circuit for the dash lights.
The ammeter is separate and in the starter relay circuit. I am basing this on a Lucas gauge installation booklet. Send me a PM and I can mail you the booklet. The illustration and lettering of the booklet
are so small that trying to email it won't work, I've tried in the past.
Tom S.
 
Wiring a voltmeter is easy. Since you are negative ground, connect the negative lead to ground and the positive lead to a green or white wire. A standard 2" (or some call them 2-1/8") gauge will fit the original ammeter hole. You'll probably want to wire it's light into the dash lights (also easy).

But don't be surprised if it doesn't quite indicate actual battery voltage. The original ignition switch has a bit of a voltage drop.

You can keep the ammeter if you want. If you remove it, you'll need to join the two or three wires from the back of it together securely.

It's actually not difficult to make the original ammeter work correctly with an alternator, but you'll have to wire it differently than Triumph rescue said to do. I did my first conversion over 30 years ago and it worked just fine for me. Search the archives for "shunt".
 
number6 said:
Yes, you can have both. The volt meter power is picked up from the ignition switch and the other terminal is grounded. Illumination is simply tapping into the light circuit for the dash lights.
The ammeter is separate and in the starter relay circuit. I am basing this on a Lucas gauge installation booklet. Send me a PM and I can mail you the booklet. The illustration and lettering of the booklet
are so small that trying to email it won't work, I've tried in the past.
Tom S.
Click to expand...

Thanks for the offer of the booklet Tom but I thnk I have enough info now to wire it up. Thanks to all who responded.:eagerness:
 
Harbor Freight also has an inexpensive voltmeter that fits in the original hole. One other issue I discovered is that depending on where you get your green wire to power the voltmeter you get a significant drop at the gauge when you turn the lights on.
Charley
 
It is a meter that you don't look at all the time. It is useful to determine battery or generator issues. I installed a car charger recepticle and stick a voltage meter into that when I think I need it.
 
Jerry said:
... I installed a car charger recepticle and stick a voltage meter into that when I think I need it.
Click to expand...

Me too (using a 'cigarette lighter' socket).

Voltmeter%202_zpsdmfntuqb.jpg
 
Hi,

I have a small LED that changes from green to yellow to orange and then red, depending on the voltage. Its a about 1/8" in dia and real easy to hide. I have mine on a separate gauge panel. One of the companies that makes the flashing brake lights has it.

Roy
 
I wanted to add a voltmeter in addition to the original Ammeter on my TR-3a to monitor the performance of an new electronic regulator that I installed recently. Since I converted to negative ground when I rewired the entire electrical system, I thought it might be handy to add the capability of powering other gear through an old style lighter socket and USB ports. I found a combination unit on Amazon and it works great. I mounted in a bracket the sits on the top of the transmission tunnel under the heater unit. It works great. It's out of the way and it's situated so a quick glance shows me the current voltage out put from the regulator. I'll attach a photo that might be hard to see, but you'll get the idea.

20160225_154054.jpg Voltmeter.jpg
 
Couple of things:
Depending on how your Alternator conversion was done, your ammeter may not be accurate, or in some cases not connected at all. Some connect the ammeter directly to the battery, bypassing the old voltage regulator and ammeter completely.
For the voltmeter, you want to connect it to the switched power so you're not drawing power while off.
These wiring diagrams are nice: https://www.advanceautowire.com/tr24a.pdf
 
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