Alternator problem - anyone care to guess at cause please?

[Guest wunntenn]

Wonder if anyone can shed light on my alternator problem.

Replaced the alternator a couple of months ago with a new Lucas one. It fired up fine and the IBS battery monitor/split charging system LED lights all lit up to show it was working fine. I checked voltage delivery with my meter and it was all spot on.

Yesterday (3/4 of the way to get the ferry to an island) I realised the LED lights on the battery monitor had diminished (theres a vertical line of them to indicate strength of charge current). I switched off heater fan, radio, etc and used wipers minimally and watched the LED’s and although there was charge coming in it dwindled then faded out completely. I got to my destination ok.

I’m now on the island (but stranded as the ferries are cancelled because of the stormy weather), so yesterday morning I pulled the various intake pipes off that side of the engine to got access to the rear of the alternator. All the connections seem fine, no breaks. Ran the engine again and initially the alternator seemed to work - the alternator tester I’ve got showed it was pushing out over 14V, however the red warning light for over-voltage was lit too, but it only lasted for a few minutes then all the LED indicators slowly faded, so no current.

I got in about it again and added a long wire to the main alternator terminal and led it out into the cab and checked the voltage delivery on the new wire in case the existing old wire had a break somewhere. The meter showed that the alternator was not putting out any current at all.

This morning (still stranded!) I started the van up and the indicator light showed that the alternator was working again, full output according to my meter - over 14V but it only lasted 5 minutes then faded out and stopped charging.

Curiously when I was using the CTEK charger with batteries in situ the IBS battery monitor showed a red light indicating and over-voltage state. I also have a Merlin Smartgauge which has also flagged up an error code that indicates over voltage.

So what might be happening here? Is it possible that the CTEK charger can have delivered over-voltage thus causing the error codes, but is it possible that in doing so it could have affected the alternator’s voltage regulator?

The batteries are ok - main one is an older Optima Red Top and aux battery is a Numax only 6 months old. But I’ve been having charging problems, and getting error codes on my Eberspacher heater controller which shuts down and indicated these are under voltage shutdowns. So something is seriously wrong and I’m at a loss to figure out whats causing it.

The rev counter wired to the W terminal on the alternator is working fine, the rev count seems spot on. So is it possible for there to be no charge current delivered, but have the rev counter working ok?

Is it possible to trash a voltage regulator on an alternator - and if so how would that occur? (in case it's something I've done)

Or am I just unlucky and got a duff alternator?

[vulcan bomber]

A battery charger puts out a higher voltage than an Alternator hence your overvolt warnings.

We need to know exactly what your Alternator is putting out and when.

Due to it being fitted not very long, are you sure the pully and belt are both tight.

[Guest wunntenn]

Yes belt is tight, but I'll need to check the pulley - I didnt think of that - maybe its loosened itself. Good thinking. Will have a look!

[Guest wunntenn]

Quick check, long bar and socket - pulley as tight as when I fitted it. So thats not the cause.

[Guest wunntenn]

"...what its putting out and when"

With the engine running first thing in the morning my meter connected to the rear of the alternator shows 14.4v. Within 5 minutes it dwindles to 0 V. Its done this three or four times now, consistently, over the last 72 hours.

The solar panel is putting out around 5V in weak sunlight and I can detect that at the alternator. If I switch the panel out of the circuit, with the engine running I'm generating 0V.

[steve b]

It should show battery voltage on the main current wire -brown- at all times , regardless of alternator activity .

If 0v is correct you have a break in the main current wire

cheers

Steveb

[Guest wunntenn]

It should show battery voltage on the main current wire -brown- at all times , regardless of alternator activity .

If 0v is correct you have a break in the main current wire

cheers

Steveb

Thanks Steve - I've misled you there - I can get the battery voltage at the alternator through the brown wire.

Which I assume indicates the main wire is intact.

I've added a second wire to the alternator output to check this, and with the engine running, batteries disconnected, I'm getting 0V on the new wire when run to earth. Which I assume means the alternator is putting out 0V.

But you've made me rethink - I was working outside in carp conditions - hurricane force wind and hailstones thanks to Storm Gertrude so my haste might have got me muddled - I'll have another more methodical check over tomorrow in daylight.

Thanks for the help.

[Peaklander]

I might be wrong but I don't think that the alternator will deliver much if it's not under load - so disconnecting the batteries to measure the output may not be a good test. I know that doesn't find you the problem but...

(In fact you might damage it with no load)

[steve b]

Yep I'd agree , although I've never tried that . If the vehicle runs it must be producing something to keep the FP sol. on .....

A better test would be to disconnect the main current wire and stick an ammeter in the connection and then run it . The ammeter would need to be 50a to cope with the charge spike on start up

...of course if the batteries are fully charged the alt. won't do much amps wise , the voltage when running should be 13 - 14.4v iirc

cheers

Steveb

[Jocklandjohn]

Thanks chaps - I greatly appreciate the advice. I'll have another go tomorrow, and proceed with caution.

[Guest wunntenn]

Re-reading my previous comments - I didn't run the alternator disconnected from the battery. I recalled reading one of vulcan bomber's posts from yonks ago saying that was a bad idea. So ignore that previous remark.

Ok out in the snow for a bit, with an alternator tester connected to the battery, and a voltmeter on the Pos and Neg terminals AND on the new wire I've run from the alternator terminal (returned to earth through a test meter) and here's what I've found:

Engine off, no battery charger overnight.

Reading at battery: 12.52v

Reading at alternator: 12.52v

Ctek battery charger on (inital charge state):

Reading at battery: 13.55v

Reading at alternator: 13.55v

This rises as the charger cycles, and both readings (at alternator and at battery) are exactly the same.

Battery charger off, but now with engine running

Reading at battery: 12.7v

Reading at alternator: 12.7v

Rev engine - no sign of alternator generating current. Check pulley and belt, both tight and spinning. Rev counter off W terminal shows idle as 850rpm.

Add load - all lights on - alternator does not respond to load and generates no current. Alternator tester confirms no charge current at battery, and meter shows no additional charge at alternator via new wire. Both devices indicate slow drain of current as loading reduces battery capacity.

Charging and monitoring devices

IBS battery monitor relay clicks in ok to indicate split charge when Ctek charger is on, and the LED lights all glow to indicate charge to main and aux batteries. This charge state and voltage is confirmed by test meter connected to batteries and at alternator.

Two permanently connected guages (on solar circuit, and a separate monitor) both show exactly the same readings as the test meter was indicating.

Conclusion

As the readings at battery and alternator agree, and change according to load or charge, I'd say the wiring is intact.

I feel confident to guess that the alternator is kaput. Anyone agree?

[qwakers]

does the battery light on the dash come on when ign is turned on and (in this case) stay on when started or go off once started? iirc the alternator gets its exciter current though the light on the dash so if that bulb has blown or the wire broken the alternator wont produce any current...

or the alternator is buggered. either works for me

[vulcan bomber]

As above really, assuming the excitor circuit is intact, your new alt is duff.

[Guest wunntenn]

Update

Checked ignition light - comes on ok. Goes off when it starts.

Got a hold of an old alternator from a pal who's got it off his van whilst he does some rebuilding - fitted it an hour ago and it works perfectly.

Puts out 14.30 V at idle. With heater fan on and lights on full beam it drops to 13.76V at idle. These are consistent readings at both alternator and battery.

So, pretty safe to assume the new alternator is knackered.

Thanks for the help chaps.

[Bowie69]

Replacement sounds good to me

[Tanuki]

I've seen similar issues when the brushes in an alternator are sticky in their carriers: they lose contact with the slip-rings and then there's no energising current fed to the rotor so the alternator stops producing a sensible output.

[Peaklander]

Yes well done - in difficult conditions!

A swap-out with a known good unit is a good diagnostic method in many circumstances.

[Guest wunntenn]

I've seen similar issues when the brushes in an alternator are sticky in their carriers: they lose contact with the slip-rings and then there's no energising current fed to the rotor so the alternator stops producing a sensible output.

Hmm. What puzzled me was that the W terminal output to the tacho was ok and spot on, so I assumed that the alternator must be ok, and that the lack of current from it was due to a dodgy connection or broken wire. And that prompted me to have a go at fixing it.

So, in the teeth of storm Gertrude and horizontal hail, by the side of the road on an island off the west of Scotland I did my manly thing and dismantled the intercooler and turbo piping to get access to the back of the alternator, only to discover it was all ok.

The ferry home was cancelled anyway so I had plenty of time to mess around!

I've got a good sleeping bag so spent a cosy night in the back of the van in a forest out of the worst of the gale, and listened to the hailstones batter down, then the snow. The temp went down quite rapidly and at one point in the small hours I peeked at the in/out temp gauge (In-fridge and out-van) and it was showing 5 deg in the fridge and 2 deg in the van!

Ah the Land Rover experience - dont you just love it!

Caught the first ferry off next morning - which might have been the only ferry as the sea was lumping up good style, and then did more manly stuff and towed a BMW up the hill in the snow on the other side, as its fat tyres gave it no grip at all, then nursemaided the young couple over the mountain pass and back to (almost) civiization. They were on holiday and not quite prepared for an arctic blast. The Land Rover might have looked the part but with no heating inside I was sitting with my feet in a puddle of almost frozen slush. Still it was only 130 miles back home.

[Aragorn]

The W terminal outputs unrectified AC directly from the windings.

The main output comes off after the diode pack. Presumably something in there was broken.

[Guest wunntenn]

The W terminal outputs unrectified AC directly from the windings.

The main output comes off after the diode pack. Presumably something in there was broken.

I'll say one thing about problems like this - your knowledge and trouble-shooting ability increases exponentially!

[defender dinky]

old guy told me once check alternator start car headlights on rev up if lights get brighter alternator ok if not renew, dd

[Bowie69]

That's a very.... limited test in all honesty.