Rangie niggle

In addition to the above, my rev counter is showing virtually 0 at tick over and eratic throughout the rev range, this, i have heard could be symptomatic of a failing alternator?????????

AlunP

The rev counter is driven of the altenator. What voltage are you getting across the battery terminals when the charging light is glowing? (put a multimeter set to 20v on pos and neg of the battery) I suspect the altenator is overcharging.

On or around Mon, 28 Jun 2004 07:12:27 +0100, "Alun P" enlightened us thusly:

you can get silly faults like this.

sometimes it's down to slightly-dodgy rectifier diodes or regulator in the alternator. I've had this one on several vehicles, and all the time it still charges and starts OK I'd ignore it. Be worth checking that the wiring isn't touching anything that allows current to leak from the small alternator wires to earth.

the battery light lights by having a supply to one side of it and the other side going to the alternator, where it's earthed when the alternator is off-charge (mostly when stopped) This supply also jumps-starts the alternator initially, since it'll not self-excite like the old dynamos used to (hence it'll not charge a completely-flat battery), and if the wire becomes disconnected than it'll not charge.

On or around Mon, 28 Jun 2004 07:30:52 +0100, "Alun P" enlightened us thusly:

can be, or can be symptomatic of dodgy connections on the back of same. Having said that, the thing with the red light does point to an alternator fault.

Evening Alun,

for the last 4 years my rangie (since I got her) has done the same thing. Every time she's gone in for servicing they do a charge test, and everytime its fine.

My advice at the moment would be "let it ride"

Si

In news: snipped-for-privacy@uni-berlin.de, simonk expelled:

As someone else has posted it will be one of the rectifier diodes not working. My father's series has done this for the last 4 years without showing any problems. Maximum output is probably down a bit but shouldn't really matter. However there is probably a fair bit of HF noise getting into the system which may not be good for all the elctronic bits (ECU et al).

Thanks all for your responses.

A charging check showed all was ok and that the battery was fine and fully charged, however, clearly the alternator is not functioning correctly. The most annoying element is the erratic rev counter, that realy bugs me!!!!

So, i bit the bullet, bought a recon alternator for £68 yesterday as the auto electrician said that the symptoms are exactly what he would expect should one of the diodes be faulty, it could last for years or totally fail next week.

Apparently the alternator, with a faulty diode, is only working in 2 phases instead of 3???????

Yet to fit the new alternator, but better safe than sorry, at least i will have a working rev counter!!!!!

Thanks once again for the accurate diagnosis.

AlunP

On or around Thu, 1 Jul 2004 07:00:48 +0100, "Alun P" enlightened us thusly:

the alternator generates AC. how many phases depends on the alternator, in fact. each phase uses 2 diodes (IIRC) to rectify the AC into DC, and a regulator is normally (these days) built into it to control the output, it does that by responding to the output voltage and supplying more or less current to the rotor, which results in more or less magnetic flux and more or less output from the stator windings for a given rotation speed.

once had a crappy honda bike which had 3 phases, and only employed 1 of them when the headlight was off, switching on the headlight also connected the other 2 pairs of coils in the stator. That was a permanent magnet thing though, and as such it produces maximum output all the time. most bikes waste the spare power thus generated through a fat resistor, the idea of switching off 2/3 of the alternator when you had not much load running was in fact quite clever - not as good as a variable-output device, but easier to make.

rev counters run from an unrectified phase, somewhere, and count pulses.