Off the car Alternator test?

[Mad smart person]

Greetings All, slight problem, how does one test an alternator when it's not attached to the engine. A Smart alternator that is. It was tested by an auto electrician and declared dead! Funny, as it came from a car that had another problem - a dropped valve and not a faulty alternator. So, is there any 'tricks' to being able to test a Smart alternator on the bench? I'd suspect that clamping it in a vice, applying 12 dc across the 'HP' terminal to ground and then rotating the pulley clockwise, should produce volts at the discharge stud, from between 13 to 16 volts. Or, am I smarting up the wrong tree?? Any suggestions?? Or do I have a dead alternator? Cheers, Ian.

Off the car Alternator test?

[madDan]

Re: Off the car Alternator test?

You probably need to activate the excite line to get the rectifier pack to chuck out some Jolts, ask Kane he has had some funand games recently with alternators and may know which line, there are differing alternator types fitted accross the smart range that don't all operate the same though.

[Evilution]

Re: Off the car Alternator test?

Don't talk to me about bloody alternators, lol.

The assumptions I will make here is that the alternator is a 3 pole alternator that requires a diode lead attaching to the centre post and earthing.
I also assume that the tester guy took it from the car to test it and didn't know it needed a diode lead and tested it without which is why it didn't output a voltage.
Alternatively he may have tested it in the car and the diode lead may be faulty. It is far more likely he just put a multimeter on the battery and saw 12 volts when the car was running and just took it as read that the alternator was shot.

If the alternator wasn't charging you'd only be able to drive it about 5 minutes before it started freaking out and the battery light would be on.

It's tricky but possible to see the back of the alternator when it is in-situ. If all 3 poles have a wire coming from them then it's probably the diode lead that's faulty that attaches to the middle pole.

[Mad smart person]

Re: Off the car Alternator test?

Greetings Kane, thanks for the info. I have no idea of the # of poles and the post that is the 'middle' one, does not appear to have anything ever attached. I've heard and read a little of this 'diode' but where, how and what is it attached to, other than the middle post? And what sort of diode is it? I was not able to see what the auto sparky did to test it, was just told it had no output! The other problem is, that I have no knowledge of the history of this alternator, other than it can off an engine that was replaced because of low compression. I'll 'ave a go this weekend and clamp it in the vice, apply 12v spin it over and see what comes out of it? Cheers.

[tolsen]

Re: Off the car Alternator test?

To test an alternator without proper gear:

1) Clamp alternator in a vice.
2) Connect a starter battery to earth and to plus terminal. There should be no sparks when connecting and no resistance when spinning alternator.
3) Now connect to field using a separate wire from battery plus with test lamp in series. Test lamp should light up. There should be a noticeable resistance when spinning alternator. You won't be able to spin alternator sufficiently fast for test lamp to extinguish.

External diode lead is only external surge protection in my opinion. Someone please prove me wrong there.

[Evilution]

Re: Off the car Alternator test?

Someone please prove me wrong there.

For once, I disagree with you. When the diode lead becomes faulty the alternator stops charging, when it's replaced it starts charging again. I can't see the alternator being clever enough to know if a protection diode isn't in place (having looked at the basic internals of the smart alternators).

I have a feeling that the diode lead is the earth return for the exciter positive voltage instead of earthing to the case.

[tolsen]

Re: Off the car Alternator test?

For once, I disagree with you. When the diode lead becomes faulty the alternator stops charging, when it's replaced it starts charging again. I can't see the alternator being clever enough to know if a protection diode isn't in place (having looked at the basic internals of the smart alternators).

I have a feeling that the diode lead is the earth return for the exciter positive voltage instead of earthing to the case.

A failed zener diode lead usually conducts both ways so alternator does not get excited and no longer charging battery. Also, in support of my understanding of how older Smart alternators are wired, I have read on forums that members have measured +12 V at the PHIN terminal when ignition is on. Would be kind of useful to learn what PHIN means. Phase Internal? B+, D+ and W are all self explanatory. Good mine only has B+ and D+ terminals and no PHIN.

[Evilution]

Re: Off the car Alternator test?

Yes, PHIN is either Phase Input or Phase Internal. The PHIN wire goes to the ECU and this goes live as the car starts to excite the coil.
I don't know if it ever goes low/turns off when the alternator starts to charge though. After changing my alternator twice I made some extension probes for my multimeter that can reach into the back of the engine and touch the connections for testing so I may test to see if the ECU line ever drops. I suspect if it does it'll only be over a certain RPM.

I suspect the diode protects the ECU if anything. When the diode breaks down perhaps it is sensed by the ECU and that line stays closed.

[tolsen]

Re: Off the car Alternator test?

On alternators with PHIN terminal, both diode lead and the thinner lead that is +12V when ignition is on connect to PHIN terminal. Normally no connection to D+ (field) and one connection to B+ (battery). Diode lead must contain a zener diode and is there to limit build up of high voltages that would otherwise cause damage to electronic control units such as ECU, ZEE, KI, ABS etc. Bad contact at battery is sufficient to cause a damaging high voltage and meltdown.

[Mad smart person]

Re: Off the car Alternator test?

Greetings All, right-ho, did as Tolsen has suggested. Alternator clamped in vice, body of alternator connected to (-) side of battery. continuity ensured through earth by connecting the test lamp to the body of the alternator and (+) terminal of battery. Now did as was suggested, connected (+) terminal of battery, via another wire, to the 'ph' stud. Alternator now gives out slight 'hum'. Rotated pulley, turned freely. Now connected 'load' light to 'volts out' terminal on alternator, light did not light and no change to force required to rotate pulley. All this seems strange, as the alternator should be a 'good' one. Either this thing is VERY smart, too smart for me OR it's a dead alternator. Is this so or is it just the way it is???????????? And the only way to really it, is put it on a motor?????????
Cheers, Ian.

[tolsen]

Re: Off the car Alternator test?

Greetings All, right-ho, did as Tolsen has suggested. Alternator clamped in vice, body of alternator connected to (-) side of battery. continuity ensured through earth by connecting the test lamp to the body of the alternator and (+) terminal of battery. Now did as was suggested, connected (+) terminal of battery, via another wire, to the 'ph' stud. Alternator now gives out slight 'hum'. Rotated pulley, turned freely. Now connected 'load' light to 'volts out' terminal on alternator, light did not light and no change to force required to rotate pulley. All this seems strange, as the alternator should be a 'good' one. Either this thing is VERY smart, too smart for me OR it's a dead alternator. Is this so or is it just the way it is???????????? And the only way to really it, is put it on a motor?????????
Cheers, Ian.

I see you did not follow my instructions to the letter. Hum is a good sign.

[Mad smart person]

Re: Off the car Alternator test?

Greetings All, right-ho, which letter didn't I follow??
I'm the sort of chap that'll be happy, all day, if somebody gives me a piece of paper with 'PTO' written on both sides!!!!!
Cheers, Me.

[Mad smart person]

Re: Off the car Alternator test?

Greetings All, the saga continues, hum or not - it still won't light the light. I've just spun the alternator up to about 1100 rpm.
Cheers, Ian.

[tolsen]

Re: Off the car Alternator test?

Greetings All, the saga continues, hum or not - it still won't light the light. I've just spun the alternator up to about 1100 rpm.
Cheers, Ian.

Connect test lead with light to D+ and see what happens. What terminals do you have and what is marked on them?

[Evilution]

Re: Off the car Alternator test?

Mad smart person, let me know the full VIN of your car and I'll look on EPC to see if it needs a diode lead.

After a good while staring at the EPC it would seem that the:
diesel 450 does have a diode lead
700cc 450 doesn't
Roadster doesn't
600cc 450 some do, some don't

Diode lead must contain a zener diode and is there to limit build up of high voltages that would otherwise cause damage to electronic control units such as ECU, ZEE, KI, ABS etc.

But that wouldn't explain why it doesn't charge when the diode breaks down. If it is there to protect the ECU then the ECU would have no other way to detect a surge or high voltage as it's relying on the diode to protect it. If it has no detection then it wouldn't know if the diode was faulty or not. The ECU would still output the exciter voltage so the alternator would still charge.

The diode lead is just a short lead that connects from the alternator to the car body earth from what I remember reading on another thread.

I'm not doubting you, just trying to justify how it all works and what it's for.