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Slightly in the positive is good. It should go higher just after starting as the battery is replenished. If it goes into the negative, say with the headlights on, heater fan on, radiator fan running then the battery is discharging and your alternator might be not up to the job.

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it should read zero ie straight down when working correctly. If yours is reading 'positive' it is either charging the battery or a load has been put on that side of the battery and you alternator is powering that device, causing a current to flow across the ammeter so it looks like the battery is charging. This can happen when, for example, an electric fan is run from the battery post and switches on.

 

Has it always done this or has it started after a new accessory has been added.

 

R

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Assuming it's wired correctly, when there is a net current flow into the battery, ie charging, it should show a positive deflection. The cell voltage of a fully charged lead acid battery is about 2.1V, so let's be generous and say 13V total. The alternator should push the battery terminal voltage to around 14V, so with no other draw, other than ignition, it's very likely that there will be a positive current flow into the battery. Thus the needle will show a slightly positive deflection during normal running. Mine always have.

 

Fair point Al. What does "near the positive" mean. I assumed a slight positive reading. If it's end stopped something's wrong.

Edited by peejay4A
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Sorry to jump in here but can anyone tell me how the ampmeter should be wired (looking from the front). Mine hits the end stop after starting, the sits about 1/4 from then on. Alternator is 45 amp replacement and Lucas pump wired via relay from starter post.

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Robin

 

I will have a look tonight but from memory alternator feed (brown and white) comes in on left side and battery is on right side. Using water analogy when alternator is chagrin battery current flows across ammeter and deflects right towards the battery side.

 

For the guy with the 45amp alternator I found that running th original with my 55amp resulted in a massive swing to the right as, following my usual good old crank to get started, the battery drew c 40amps. I didn't like this - having blown on ammeter and so I fitted a smith 60amp ammeter and have disguised it as a Lucas's using and old 30amp lucas innards - still wip as it is too bright when lights are on. The connectors here are a pain - 2 9.5mm terminals so I has to buy a 4 way connector from revington so u could wire in alternator feed, feed to ignition switch and fuel pump.

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Robin

 

I will have a look tonight but from memory alternator feed (brown and white) comes in on left side and battery is on right side. Using water analogy when alternator is chagrin battery current flows across ammeter and deflects right towards the battery side.

 

For the guy with the 45amp alternator I found that running th original with my 55amp resulted in a massive swing to the right as, following my usual good old crank to get started, the battery drew c 40amps. I didn't like this - having blown on ammeter and so I fitted a smith 60amp ammeter and have disguised it as a Lucas's using and old 30amp lucas innards - still wip as it is too bright when lights are on. The connectors here are a pain - 2 9.5mm terminals so I has to buy a 4 way connector from revington so u could wire in alternator feed, feed to ignition switch and fuel pump.

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If it's just started to do this it could be either the battery failing or the alternator output is uncontrolled. Can you measure the battery voltage when this is happening?

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From memory I have one large brown feed (from alternator) and 2 brown and white , will check when I get hone.

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ntc, my wires are the other way round....no doubt i put them back on wrong...deflects right when charging the battery and left when the battery is powering everything else !

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yep - could the OP check the brown and yellow wire to the alternator is still plugged in (if they get no voltage on that line then there is no field to allow the alternator to work and the battery is just on full discharge for pump ignition etc.)

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I could be wrong but I think that maybe the OP's original point is being lost. His problem seems to be high charge rate, not discharge. I suppose the field connection might have something to do with it but if the charge warning lamp comes on before starting and goes out when running it suggests not. Does it?

Edited by peejay4A
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OP says his wires are reversed compared to ntc.

 

So I guessed he had discharge rather than overcharge.

But it was a guess. We don't really know yet.

 

All we really know for sure is the meter is end-stop.

We don't even know if someone else has fiddled about.

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Guys, Neil, looks like I'm sorted. Two brown white on right, brown feed from alternator on left (when facing front of ampmeter), my mistake is I'd wired the third brown/white to the ampmeter when it should have been to ignition switch. It feeds the lights, so now have two brown/white on ignition switch and two on ampmeter. Now I get either an extra positive charge when lights on an engine running and extra negative when engine not running, as you'd expect.

 

Thanks again, now off off a spin in the sun....

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OP says his wires are reversed compared to ntc.

 

So I guessed he had discharge rather than overcharge.

But it was a guess. We don't really know yet.

 

All we really know for sure is the meter is end-stop.

We don't even know if someone else has fiddled about.

It was snowric who has his wires reversed. The OP hasn't mentioned it.

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