Where's your needle?

[jjbunn]

I have become suspicious of my old alternator for a couple of reasons:

1) the Ammeter on the dash only ever moves into Charge when I first start the engine: it momentarily zings up there, but then comes down to middle position almost immediately (initially I thought this was caused by a loose fan belt, but I checked and it seems tight),
2) it's an old 5 terminal type, and the PO had a refurbished 3 terminal replacement sitting in the trunk, which he'd never fitted. Makes me think that he'd identified the old one as bad, and intended to replace it.

Question: with the car in motion, with lights, blower etc. off, where should I expect the ammeter needle to be?

Anyway, yesterday I removed the old one, and installed the refurbed one, which is a 3 terminal 43 Amp device. I have the conversion kit from Moss for going from 5 to 3 connector. I'm about to tackle the wiring.

In fact, the Moss/Lucas instructions specify connections only to two of the terminals: positive wire to one of the big alternator spades, and IND wire to the small alternator spade. Trouble is, I appear to have two IND wires - looks like I'll need to explore them with a multimeter.

There is a black wire that currently goes to the engine block and is apparently not needed with the newer alternator. I thus assume that the alternator case bolted to the engine provides the earth. Is that correct?

 

[TR3driver]

1) the Ammeter on the dash only ever moves into Charge when I first start the engine: it momentarily zings up there, but then comes down to middle position almost immediately

Sounds perfectly normal to me.<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Question: with the car in motion, with lights, blower etc. off, where should I expect the ammeter needle to be?[/QUOTE]If the battery was heavily discharged (eg car was hard to start or has sat for a long time), then you would expect it to show charge for some length of time. After that, the ammeter should read zero (neither charge nor discharge).
If you've done something with the engine running to discharge the battery a little (like idling at a stop light with headlights, heater, etc. on), then you might see a little charge again when you resume driving.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Trouble is, I appear to have two IND wires - looks like I'll need to explore them with a multimeter.[/QUOTE]Likely the other one is a brown 'sense' wire. Check it out.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]There is a black wire that currently goes to the engine block and is apparently not needed with the newer alternator. I thus assume that the alternator case bolted to the engine provides the earth. Is that correct? [/QUOTE]That is the theory; but keeping a separate ground wire certainly won't hurt anything. Most alternators have provisions to attach one somewhere.

 

[jjbunn]

Randall: spot on - the other is indeed a brown sense wire, on closer inspection.

I'm not familiar with having an ammeter, I'm more used to a voltmeter, which when the car is running tends to go up to 14V or so ... I think I'd put two and two together and made five, thinking that the increased voltage implied that with an ammeter should see significant charging amps. But that would only be true if the battery was discharged (right?).

Do I need to connect that somewhere? Looking at the Dan Masters wiring diagram, I don't think I do.

 

[TR3driver]

Right. You should only see charge when the battery needs to be charged. "Normally", the battery is fully charged and the alternator supplies all the current that the rest of the car needs, so you see no deflection on the ammeter.

If your alternator has a 'sense' input (which would be a separate terminal, not part of the 3 terminal connector), then it should get the small brown wire. But most replacement alternators don't have the sense input, so you can just insulate and tie back the wire.