[Mgs] 54 TF ammeter question

mgbob at juno.com mgbob at juno.com
Sun Jan 18 08:59:58 MST 2015

  A couple of questions, then ideas:  When engine revs increase, does the ammeter needle move farther?  When engine is off, headlamps switched on, does ammeter show charge or discharge?  Which way does the needle move when ignition is switched on?  Did you polarise the dynamo after making the polarity change?  Did you test the gauge when it was out of the car?  If you have not polarised the dynamo, do that first, then run the tests again.  Should needle move farther to - when engine revs, the gauge is probably connected backwards. How would I know--did it myself last summer, despite having new harness and having marked the back of the ammeter.  Upside down, backwards, in the dark shadows, under the dash panel, wires seem to challenge the owner.  If needle moves to charge when ignition off and headlamps on, it confirms that gauge is wired backwards.   Did you polarise the dynamo after making the polarity change?  The procedure is in the manual--easy to do, though the spark can be startling.  Manual also has a good explanation for testing output of dynamo and the control box.  The area of concern here is that all the electricity in the car, except for the starter, runs through this gauge, ignition on or off, so one wants to be comfortable that all connections are sound. Bob

---------- Original Message ----------
From: dontoy--- via Mgs <mgs at autox.team.net>
To: "" <mgs at autox.team.net>
Subject: [Mgs] 54 TF ammeter question
Date: Sun, 18 Jan 2015 15:24:12 +0000 (UTC)

Dear listers, 
I have a 1954 TF which my father drove home from Pittsburgh in 1971. After an electrical problem way back then the ammeter got fried, along with damaging the temperature gauge. In an effort to go back to original I sent both units out for restoration to MoMa. I installed the temperature gauge first and it went up to 185* and held it there. That made me smile. Then I installed the ammeter. Since I had did the polarity switch (now a negative ground car) I wasn't sure which wire went on which terminal. I just guessed and put the brown with white on the left terminal, the solid brown on the right.  Of course upon starting the car, the ammeter ran in the negative side. 50% chance and I guessed wrong. So I thought. After reversing the wires I got the same result. I know I'm charging since I have never had a problem. I don't run a trickle charger and can start the car anytime in go out into the garage, even after months. Is this just one of the effects of switching the polarity or is there something I'm missing. I was showing a charge on the aftermarket unit that I was trying to replace. Ideas? 
Don Toy
" all great men are dead... And I'm not feeling well"

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