View Full Version : TR4/4A Amp to Volt meter wiring question TR4

09-30-2006, 02:08 PM
Just switched out my generator to an alternator using Dan Masters wiring info for the conversion and installed a Auto Meter Amp gauge. Worked great! Now I want to go to a Volt meter gauge. What is the proper connections for the Volt meter hook up? Currently the Lg.brown (10 amp) is connected to the "S" on the Amp and the Brown/White (10 amp) and small brown wire connected to the "I" terminal. Would this be the same for the volt meter?
Thanks for the help. /ubbthreads/images/graemlins/confused.gif

09-30-2006, 03:30 PM
Greetings;hooking up a volt meter is very easy;just plug one into the cigar lighter socket,you can purchase these dedicated meters at an auto supply store.I have one from 'ROADPRO'(digital)led signals & an extra socket for another device $12.95.....kenswhitelightning /ubbthreads/images/graemlins/savewave.gif(alias 'myspitfire')

Geo Hahn
09-30-2006, 06:37 PM
Cigarette lighter??? In a TR4??? This ain't no boulevard cruiser!

A voltmeter hook up will be quite different (and much simpler) than an ammeter. One lead will be a hot wire, the other just a ground. The current draw is very low so you will not need the heavy wires like on the ammeter.

I would think you could pick up the hot side from the green wire side of the fuse block or possibly the solenoid (or goodness knows any of several locations behind the dash). For the most accurate reading the solenoid & a 14 gauge wire might be best.

I should state -- I have not hooked up a voltmeter on the TR so others may have real-life experience and advice.

09-30-2006, 09:39 PM
Are you wanting to replace the ammeter, or keep it and add a voltmeter as well?

To remove the ammeter, just remove the wires from the ammeter and connect them together. Make sure you have a GOOD connection on these wires, as MOST the current in the car goes through these wires.

To add a voltmeter, just connect the positive lead to the most convenient green wire you can find, and the negative wire to a good ground. No need to add a fuse for the voltmeter, as the green wires are already fused.

09-30-2006, 10:10 PM
As I was looking at the TR6 electical wiring diagram for something else, I see the voltmeter for it connects to the white wire that provide voltage to the low oil pressure light and the failed brake indicator light. As this voltmeter is basicly the same as taking a voltage test meter and connecting it between the + and - of the battery. It can be connected to any power wire, that gets power after the ignition switch is turned on. When the car is not running it will read the battery voltage and when the car is running it will read the voltage level that the altenator is putting out, usually approximatley 2 volts higher than the battery itself, when at a normal charge level.
14 gage wire seems abit large to me. The 6 has what I would judge to be 18 gage for this wiring. There is an article at the VTR web site on wire gage for british cars.
www.vtr.org/maintain/wiring-harnesses.shtml. (https://www.vtr.org/maintain/wiring-harnesses.shtml.)
Comcast won't let me get there tonight.
Hope this helps

10-01-2006, 09:30 AM
Take all wires that are hooked to the amp-meter and connect them together and insulate the connection . Then splice into the purple/black wire coming from the ingnition switch and connect to the positive side of the volt-meter and use a ground from the dash lights to the negetive side of volt-meter.

10-01-2006, 02:38 PM
Take all wires that are hooked to the amp meter and connect them together and hook them to the positive side of the volt meter-----hook a ground wire up to the other side. This is how I did my TR6 and has worked flawless.

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That'll work, but there are two downsides to it:

1) the voltmeter will read all the time, key on or off. This is not a major problem, but if the car isn't run for a long time, the battery may run down (even though the voltmeter is a small load)

2) There is no fuse in the voltmeter lead.

By conecting to a green wire, both of the problems are eliminated.

10-01-2006, 06:19 PM
Dan, You are right, it has been a long time since converting over to the volt-meter, I got under the dash to renew my memory. What I did was hook all the amp meter wires together and then used a purple/black wire coming from the ignition switch to power the volt-meter (it only activates with the key on) and I used a ground wire from the dash lights. Im going to have to edit my first post.