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MG TD TF 1500 - Testing Ammeter

I have a spare ammeter I want to test prior to installation, and I don't want to loose all my precious Lucas smoke in testing.

The diagram shows the ammeter wired to the hot side of the starter switch (in my negative ground car, the +) and to the "A" post of the regulator. Can I just wire the spare up this way to test, or is there an easier/better way?

Thanks for any input,

Larry
Larry Karpman

Since Ammeters carry large amounts of current, there isn't a simple way to test them. The procedure you described would certainly be a good way to see if the meter works at all. But it, of course, won't give you a clue about the accuracy of the meter.

Most digital multimeters will measure up to 10 Amps. So you could put the digital meter in series with the connections you have described and just turn on the ignition. See if the ammeter agrees with the digital meter, also try the side (parking) lamps. If those readings agree you have an ammeter you can believe.

Cheers,

Bob
R. K. (Bob) Jeffers

Larry if you have a battery charger you can wire the amp meter in series with one lead of the amp meter, and hook up charger for charging. The amp meter should
agree with the meter on the charger.

Dallas
D C Congleton

Larry, it's fairly easy to test (says the retired EE). Ammeters measure the current in a circuit and have very low internal resistance. You can connect the test ammeter in series with the car's ammeter and expect both to give the same reading. Look at the Workshop Manual Wiring Diagream on page N.23. Note that the ammeter is connected to the battery (-) terminal at one end and to the 'A' terminal of the Control Box at the other end.

Since you'll be working with something directly connected to the battery the first step is to remove the battery ground terminal. Now disconnect the (should be brown with white) wire from the Control Box Terminal 'A'. Connect this wire to one input terminal of the ammeter being tested. Connect the other terminal of the ammeter to the Control Box Terminal 'A'. You have wired the two ammeters in series. The same current will flow through both of them. Please be careful to insulate these connections from the car, or you'll loose that precious smoke.

Now, reconnect the battery ground terminal. Nothing should happen (yet). Turn on the lights and you should see the same reading on both ammeters. Anything that you do to get a reading on one meter should show up on the other. If, perchance, you wired the test ammeter up backwards you'll just see the needle moving in the mirror image of the car's ammeter.

That's really all there is to it. Good luck - Bud
Bud Krueger

Thanks for all the input folks. Looks like I have several choices. Bud, as I can't identify the Brown/White wire at terminal A (no colors left :-). I'll have to use one of the other methods.

Cheers

Larry
Larry Karpman

This thread was discussed on 17/02/2008

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