Urgent help required - Alternator problems?

[dunc]

Just drove home and the volt meter on the dash was reading between 10 and 12v while driving. Checked the battery with a multi-meter and it's 11.9v not running and about 11.5v when running, revs don't alter anything.

Is this deffo the alternator or regulator or can it be something else? All aux belts are new.

Need the car tomorrow morning but isn't looking likely [] The car's driving fine by the way but not for too long like this I'd imagine.

Is there anything easier than the alternator (or regulator) I can check or replace tonight or early doors tomorrow morning? Fuse or common bad wiring area?

Thanks in advance,

Dunc.

 

[dunc]

Forgot to mention that it's a 5 month old Bosch battery

 

[tref]

How far do you need to go tomorrow?

I travelled 126 miles when I had a failed alternator, by carefully monitoring the voltage with a multi-meter (via a pair of long leads into the boot), and all bar the first 1/2hr was in the dark, dropping to side lights when I could get away with it, and ensuring everything possible was turned off (blower motor, radio etc, etc.) It will still start and run at about 10v.

 

[dunc]

Hundreds unfortunately and already driven 45mins! I am tempted though...

Cheers,

Dunc.

 

[924nutter]

It could be something as simple as an alternator earth, but sounds like the voltage regulator. The issue will be providing enough current when you put the lights on as you appreciate. I'm hoping for you that the alternator has'nt packed up, but then in my life time Ive only known one alternator die, on my sisters mini. I replaced the diode pack and bearings and away it went. Orcam's razor.

 

[edh]

My S2 alternator died - well it was dying & pretty much fell apart when it went to be rebuilt. After 235k miles you shouldn't be surprised I guess. I had it rebuilt for £90 so not the end of the world.

 

[ChasR]

As 924 Nutter said, check the earthing points and ensure that the strap is good. After which I would put a multimeter on the battery and see what you are getting with the car running.

Like many, I have sufficed with a shot alternator on a few occasions and with some careful though have managed to coax the car back.

 

[dunc]

Thanks for the advice, made do by using a few batteries. The running and non-running values were as above after I had been poking around. The wiring at the alternator is tricky to get to under the black cover on the alternator. The battery earth is fine, the belt is fine and looking under the black cover it seems OK.

What's my next step, buy a new voltage reg. and try that then a working alternator (or rebuild) if that doesn't work?

Thanks,

Dunc.

 

[924nutter]

Check the terminal on the back of the solenoid. The alternator usually just take voltage to there, and into the battery, via the starter motor lead, although on the rear batteried 944 I seem to remember a separate red cble. What I am really saying is check all the electrical connections are clean and tight. Yes the alt on a 944 is a bit of a pain becuase of the tensioning turnbuckle.

 

[Mike_Pollock]

Yes - regulator

Easy swap - just getting at it in situ is hardest bit

Mine had one totally worn out brush, the other was half worn!

 

[dunc]

Thanks, is this possible from the top or do I need to get underneath?

Also I'm a bit confused by the two types?:-

http://www.ebay.co.uk/itm/Alternator-Voltage-Regulator-for-Porsche-944-81-91-/380463050556?pt=UK_CarsParts_Vehicles_CarParts_SM&fits=Model%3A944&hash=item58955d6f3c

or:-

http://www.ebay.co.uk/itm/Porsche-944-924S-924-968-928-964-993-alternator-voltage-regulator-/121191496684?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item1c37937bec

They're not even similar or am I being silly? Also is this fitted on the back of the altenator under the black cover?

Cheers,

Dunc.

 

[dunc]

Another possible silly question, the engine mounts were just replaced at a garage I assume it couldn't be related to this?

Dunc.

 

[ChasR]

The listing that GSF have up I suspect is a false listing. It does happen (try searching on ebay for a 944 AFM in new condition and you shall see what I mean.

The item from FrazerPart should do the job .

 

[dunc]

OK cheers

Any opinions on the other questions - access an location to it?

Thanks,

Dunc.

 

[924nutter]

Well I peeled some potaotes last week maybe it's my fault. Seriously though the alternator earths to the engine which in turn earths to the vehicle body by a braid. check that the braid is doing its job. I am no expert on 944, but if it is arranged anything like the 924 the braid is secured by one of the coil bolts on the bulhead. The process of changing the engine mounts might have caused a problem but who knows. It is another thing to check.
Alternaotrs do not have a commutator (wide slotted copper ring inside the body, turned by, and attached to the shaft. The generated voltage comes from the coil pack and enters the real world via the + teminal on the back, with no moving parts. The volatge regulator controls the field winding voltage (thus magnetic flux, ergo output voltage) via two slip rings which the brushes in the voltage regulator rub against as it rotates. the slip rings have no slots in them. it is highly likely therefore that the voltage regulator is attached in someway to the back of the alternator. Do yourself and your paintwork a favour and access the alternator from underneath; it does mean taking off the undertray but as in many walks of life, working on your back is better than bending over. Have 7, 8, 10, 17 and 19 mm spanners handy and take them under tha car with you. The turn buckles are 17 or 19 but I can't remember. The nut on the turnbuckle you just rounded off but simply would'nt undo has a left hand thread. and due to its location underneath they will likely be quite corroded. I think the turnbuckle has flats on it and I recommend you use a second spanner on the 'buckle to oppose the loosening torque rather than rely on an 8mm bolt which often breaks. Undo both mounting bolts, and the bolts on the turn buckle swivel the alternator in and take the belt off the pulley. It could just be the belt slipping. I don't think Polyrib belts seem to squeal as much when they go because they transmit drive so well. Whilst supporting the alternator with one hand remove both mounting bolts and gradually lower the alternator to get to the terminal bolts which may be 7, 8 or 10 and now you know why you need the spanners with you so that you don't dangle the alternator on the leads whilst you try to find them.

 

[dunc]

Thanks for the detailed response, I'll get it from underneath then

The alternator is definitley turning that's one thing I have checked.

Very much appreciated,

Dunc.

 

[geoff Ives]

The easy way to check the alternator earth is to ge a jump lead, just one, and clamp it to the alternator body and the other end to th engine. Even better clamp it to the negative post on the battery. Mine is an eartly car with the battery in the engine compartment.
That will tell you if the problem is the earth.

 

[924nutter]

Good tip Geoff

 

[924nutter]

ORIGINAL: dunc

Thanks for the detailed response, I'll get it from underneath then

The alternator is definitley turning that's one thing I have checked.

Very much appreciated,

Dunc.

Unless you have arms like an octopus with an eye on the end of each finger

 

[Melv]

Oh, and for a moment I thought the OP was going to be Adrian Newey...[]