FredR

Stan,

The gauge on the dash is pegged flat at around 10 to 11 volts suggesting to me that nothing is coming through from the alternator so presumably either a diode blown or perhaps a problem with the voltage regulator.

I am assuming the hot post will see exactly what the dash gauge sees.

Regards

Fred

Mrmerlin

you need to measure charging voltage at the hot post before you take any of the charging readings as gospel.
Until this is done we are just full of conjecture

FredR

Stan,

Just ran it up measuring the hot post. Before starting the hot post read 12.3 volts, engine running it read 11.8 volts- rpm's made no difference I cukd measure. Ergo nothing coming from the power generation system for whatever reason.

Any idea how many amps are drawn running like this [no lights, no a/c etc]?

The warning system also advises no diff lock, no ABS and some mind of battery problem -preusmably because of the underlying problem.

Regards

Fred

jej3

I would make sure that all of your grounds are cleaned. Have they been cleaned recently or ever?

Following one of the ground cleaning procedures on this forum is a must do... I try to do it every year before Sharks in the Mountains.

Also, you might pick up a cheap ground cable and replace the ground cable in the rear to see if it makes any difference. You have a ground cable in the front from the bottom of the engine to the right hand side of the car. That cable never gets replaced and was absolutely the cheapest thing I ever purchased for my 928 from a Porsche Dealer.

There is likely something more dubious but I would start from the foundation that you (like everyone) will have ground problems if they aren't cleaned periodically.

You may want to also simply pull your alternator and have it tested (assuming someone can test it for you)

GOOD LUCK!

jej3

Also, I found a CE Panel Refresh (or at least replacing all of the fuses and removing/reinserting the relays) did wonders, too!

Mrmerlin

IF after cleaning all of the electrical connections,
you still have this condition,
either the belt is missing off the alternator, I know its there and tight.

OR the brushes are worn down,
Since the alternator isnt charging the usual culprit is the brushes being worn down.
If the brushes appear to be good IE they are not worn down,
then the alternator is in question,
so it needs to be removed and checked,
if the alternator is removed take some time and check that the blue wire has continuity to the 14 pin connector,

NOTE if the alternator is left dangling by its harness then a good chance the blue wire will shear off about 4 inches up from the alternator.

FredR

I had an a/c failure caused by the belt grenading but the alternator belt is all present and correct. Where exactly are the brushes you refer?

Regards

Fred

Mrmerlin

The brushes are held in the voltage regulator.
the brush holder/regulator is held to the back of the alternator by 2 screws ,
and thus the air duct needs to be removed first to get to the regulator

My suggestion to remove the alternator,

is to jack up the car , drop the alternator,
sit it on a milk crate so it wont hang from the harness,
and remove the duct,
then remove the brush holder.
Optional version loosen the alternator and swing it,
so you can remove the 4 nuts that hold the duct on,
then remove the brush holder with the alternator in place,

NOTE its a bit more tedious as the 4 nuts are sorta difficult to remove and the harness may get in the way of sliding off the duct

FredR

Stan,

Thanks for the inputs- I'll take a look on my spare alternator to see what is what. A good thing about being here is that we still have many artisans who can do real repair work. A friend of mine had his 944 alternator rewound.

When I ran the car yesterday [before getting stuck] I thought I could hear something a bit abnormal- nothing obvious -perhaps something is/was on its way out but not the kind of thing that stops one there and then.

I assume it is not too difficult to disconnect the alternator altogether. Since I purchased this vehicle 6 years ago the alternator has not been off the car -indeed I have not had a single electrical problem so probably long overdue one!

Suspect I am going to get a crap house full in one hit with this one!

Regards

Fred

Regards

Fred

Mrmerlin

If your crafty with a soldering gun and have access to a alternator rebuilder,
you may be able to buy new brushes and resolder them to the voltage regulator,
and then be on your way.
This fix could cost all of 3.00 for new brushes and a few hours of your time,

NOTE if you cant find new brushes,
do not buy an aftermarket voltage regulator,
buy a Bosch unit only,
the AM parts here dont seem to last and you will see this job is a bit tedious,
' so it pays to do it right the first time

FredR

My spare alternator got doused the other day in a down pour after the neighbors builders moved it and other items from a sheltered position whilst I was away! Still i guess bosch expect them to get wet to some extent where they are located.

I am not averse to playing around with such things. Stripped and rebuilt mum's vacuum cleaner when I was 13- brushes were shot on that. I expect diodes can be replaced if you can find the spec for them. Guess we will see what we see.

The 4mm yellow [now burnt orange] wire from the alternator did not look too clever either. I suspect some wiring replacement would not go amiss whilst at it.

Regards

Fred

FredR

Took another look at the wiring diagrams today- with the battery still disconnected I put the multi meter on 200 ohm range and measured the resistance to earth was 4 ohms!

V=IR suggests the current to earth would be 3 amps. I presume that proves beyond doubt a diode[s] is blown. Maybe this explains the discoloration of the red 16mm cable from the hot post [hotter than it should be?] to the alternator.

Just tested my spare alternator to see if there are any similar signs on this unit from the voltage out post but resistance was infinite.

So, it is either a blown diode or the 16mm cble is down to earth to for some reason- logic sound here?

Regards

Fred

FredR

Took another look at the wiring diagrams today- with the battery still disconnected I put the multi meter on 200 ohm range and measured the resistance to earth was 4 ohms!

V=IR suggests the current to earth would be 3 amps. I presume that proves beyond doubt a diode[s] is blown. Maybe this explains the discoloration of the red 16mm cable from the hot post [hotter than it should be?] to the alternator.

Just tested my spare alternator to see if there are any similar signs on this unit from the voltage out post but resistance was infinite.

So, it is either a blown diode in the alternator or the 16mm cable is down to earth for some reason- logic sound here?

Regards

Fred

Hilton

Fred, you can test an alternator roughly on the bench, with a length of strong string, and a 12V supply. Just supply 12V to the exciter terminal (ground on the body of the alternator) and pull the string after winding it around the pulley a few times. You should get enough speed up to get 13V on the hot post on your multimeter. (yes, I've done this).

I'd also have a good look at your commutator where the brushes make contact. Given the sandy climate you live in, I'd expect the brushes and commutator to wear faster than most places.

FredR

Hilton,

Interesting test- I wondered if something along those lines may be possible- might give it a try this evening. Hopefully I can air blast the accumulated crap out of the alternator body not that there appears to be too much in there.

I have been here many years and your logic about wear is reasonable but I have not come across this as a notable problem. The relatively dry climate may be compensating.

Regards

Fred