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Agrace

AMP reading

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Might be a silly question, but what reading should my AMP gauge show whilst driving?

I am showing around zero at idle and past -2 whilst driving.

 

TR4A with generator.

 

Thanks all.

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The ammeter should show zero most of the time except immediately after starting when it should show a large positive current which reduces after a minute or two as the battery re-charges. You can check correct operation of the ammeter by switching on the headlights with the engine not running - the meters should show a (-) discharge of up to 10 amps but if you do the same with the engine running at a reasonable speed, there should be no discharge shown.

 

A constant 2 amp discharge while running is probably the ignition circuit drain and this would suggest the dynamo isn't providing a charge. Do bear in mind though that these are not precision instruments - where does the needle sit with the ignition off as that is the real zero point - and also there will be a parallax error when you view the meter a little sideways from the driving seat.

Does your ignition lamp come on when you first turn on the ignition and extinguish after starting the engine?

Edited by RobH

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Andrew, I still run a generator on my 4a. the ammeter shows + 10 after start for a few minutes, then about +2 thereafter. Always has for past 40

years. Do not think - 2 is correct. Your symptoms do not make sense. You are saying the generator is pushing out more charge at idle than when

running. What is it immediately after start, if it is showing a negative figure at around 2000 rpm then your ammeter has been wired in reverse.

 

Simon

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Simon - that is why I suggested Andrew does a simple test to see whether the ammeter is wired correctly and working and that the cut-out is operating.

 

If your own meter shows +2A all the time that is maybe an anomaly that might be due to an extra circuit added on the battery side of the meter or perhaps the regulator adjustment is off so the voltage is a bit high. In theory once the battery has re-charged there should be no current flow shown on the ammeter and that is what I see on my own car. Apart from the odd twitch as you switch things on and off there will only be a discharge shown for some very large load that the dynamo can't cope with alone.

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