Porsche Enthusiasts Club Forum

Hi Folks,

I've been doing lots of jobs on my 944 Turbo over the winter and managed to get the main engine jobs finished over the weekend so celebrated with the first ignition since last August!

However I found a few issues whilst I was doing some final jobs yesterday including a no-charge condition with the battery / alternator.

I ran the engine for a good 30-45 minutes and it the voltage meter was dropping pretty low and the alternator light was on constantly along with the ABS warning light (which I understand is usually down to low voltage).

This morning I cracked out my voltmeter and read 12.6V across the battery with the ignition off and about 12.1 - 12.2 with the ignition on...

I pretty annoyed as the alternator is a pain to get to on the turbo and I'd already replaced the regulator as preventative maintenance before I re-installed it.

I replaced the regulator with a BERU GER 004 and I made sure that I cleaned up the alternator and the electrical contacts before I'd put it back together.

I've heard sometimes that a new regulator won't work as it won't "follow" the tracks that the old regulator has made on the contact bearing? Is this the likely cause - I was also very careful when I fitted it to not break the brushes.

I'm going to check continuity of the cables on the alternator next and see if I get the same voltage reading that I do from the battery - the only problem is it is impossible to run the engine whilst testing the alternator on the turbo due to the amount of stuff that needs to be removed for access!

I'm hoping this isn't going to be another huge bill as I've been looking and can see that replacement alternators range anywhere from £150 - over £500...

Thanks!

If it is a dead alternator just get it rebuilt, the normal cost is about £100, but I would take another look at the regulator first, I have done that job a few times before and put it all back and it’s not worked, taken it back out reseated it and it suddenly works

The other thing to check is did you knock off the exciter wire ?

But as I understand it, a complete pain in the ass on a turbo

Sorry posted in wrong slot

The alternator is a complete pita on the turbo. I've done it many times, so much so I've reduced the time from 4 hours to 2 hours. Given the ball ache involved I would get it refurbed as Martin suggests and reinstall with confidence. It's also worthwhile ensuring the ducting is present and correct when you put it back together as it helps charging significantly when the engine bay is hot.

Stuart

Thanks Stuart,

Yes I'm just being cheap - I had considered tearing it all down again and reseating like you said but I don't think I would be happy if it still didn't work after putting it all back again!

I see a new Lucas alternator can be had for around £250 from carparts4less.

Thanks for the tip on the ducting, I cleaned up the alternator and replaced the ducting and fitted a new seal between the plastic shroud and the alternator as part of the works I've been doing. Instead of paying Porsche £20 for a new duct I got some new neoprene sleeving off ebay for about £9 and fitted it with two new hose clamps. Front end is looking a lot more refreshed now with mostly new bolts and fittings where possible, just finished a full belts, water pump and pulleys job as well as a front end reseal. Took the opportunity to wash everything as well



Will check the obvious when I take it all apart again in case it was something silly like lack of continuity or a broken wire or installation error with the regulator.

It almost appears like I've lost one bank of diodes as that would probably equate to 2-3 volts according to some other sources I've been reading and would put me right in the ball park of 13.5 - 14.0V which is what I should expect.

Do you know of any recommended refurb places?

Cheers

Most auto electricians should be able to refurb it for you. Seem to recall paying about 30 quid off Ebay for a recon kit and paying a local guy £30 to do the job. Been fine ever since and get over 14v most of the time.

I tried a few rebuilt units from Ebay before that and they all failed. In fact I'm convinced one guy just painted them and passed them off as rebuilt!

£250 is a good price for a new one. I'd go for that if I was you.

Stuart

So I removed the alternator yesterday - such a PITA as you have to remove the turbo intake hoses, drain a bit of coolant and remove the water crossover pipe that feeds the turbo cooling circuit. Also not much wiggle room to actually get the alternator loose from the mount.

I removed and reseated the regulator, the brushes looked fine and not damaged (something I managed to do on my 944S many years past when doing the same job - but much easier on that car).

Before removal of the two cables I checked using a multi-meter and was seeing the same reading at the B - post on the alternator as the battery so the wiring looks good.

I tested the diode also but I'm getting a reading of 0.993 which seems high to me? my multi-meter instructions say it should be between 0.400 - 0.900 and most videos I watched on youtube were coming out around 0.500ish.

I'm tempted to put it back in and see if it works now I've reseated the regulator but don't want to put it all together again and find out it still doesn't work

I guess I don't need to fill up the coolant as I only need to run it for a few seconds to check the voltage reading...

Not sure what units you are measuring? 0.993 what? Ohms? There are 3 main diodes in a rectifier pack (the alternator outputs 3 phases of AC internally) & with the alternator assembled they are difficult to measure the resistance of. Also the regulator is impossible to test with a meter.
The best way especially as its a PITA to remove & replace is to get it to a decent auto electrician with a rig to test it on.
If it over charges (alternators with no regulation can output 50 odd volts) which isn't impossible then not only could it fry the battery but destroy DME, instruments etc.

Hi Jim,

Pretty sure it isn't outputting 50V, I know my way around a multi-meter well enough to know that.

I think the problem revolves around my replacement of the regulator and the old one has long gone in the garbage but the brushes were worn out anyway.

As far as I'm aware there are only 2 different regulators used on Bosch alternators of this vintage so pretty sure I have the right one, can see the brushes are contacting the tracks on the armature and the screw holes line up correctly

I tested the diodes using the method that most guides will tell you on the internet -

1. Switch multi-meter to diode mode
2. Place the red probe onto the alternator casing
3. Place the black probe onto the B post

Doing this I'm getting a reading of 0.993 which I assume is Volts and from everything I've read should be no higher than 0.900 and should be around 0.500, with the probes reversed there should be no reading or overload shown by the multi-meter (I get no reading when reversed - which should be good).

Next problem is where does one find a decent auto electrician? there doesn't seem to be any in my area apart from one dodgy looking outfit that appears to be a normal garage that does starter and alternator repairs (I'm guessing by repair they mean replacement with a new one).

It appears that the alternator is outputting nothing at all as when the engine is running the voltage reported at the battery is lower than without the engine running.

I'm also hesitant to buy a "reconditioned" alternator off ebay as I've read numerous reports that most of these appear to be cowboys too and just replace the regulator and then spray paint the alternator to make it look new.

I am sure you could rig up some kind of test yourself with a battery some wire, a jump lead or two and a vice and electric drill to spin the pulley

I bet there is a video of some kind on YouTube

Now that sounds like a great idea!

I've got visions of fixing the alternator up to my push bike with a drive belt lol

I've got next week booked as holiday to get as much sorted on the car as I can so will ring around a few places in yellow pages and see if I can find someone with a test rig that is willing to test my existing alternator.

Will let you know how I get on in case it helps someone with similar issues in future...

As an aside you do not need to drop coolant or disconnect water pipes to change the alternator on a turbo. If you remove the bolts on the inner wing (2 x 10mm I think) that hold the metal water pipe, allowing it to move slightly, then the alternator can be wiggled out! You need to wiggle it so that the fan is facing you, then with some skilled rotation it can be extracted!

Stuart

Well I ended up getting the reconditioned Lucas alternator from carparts4less, I was very impressed with the service, I got a rebuilt Bosch alternator in a Lucas box with a test certificate print-out showing the actual test results from the alternator in the box. Everything has been replaced and it looks brand new so well chuffed and it also fixed my problem and showed a healthy voltage when running! I'm pretty sure that my rectifier / diodes were stuffed as if I recall correctly before the car was taken off the road the voltage wasn't stellar but is now showing a healthy 14v on the in-dash voltmeter.

Excellent! You can work on your ABS next......

I'm hoping that the warning light will go out when I take it on a short shakedown run, I seem to remember an issue with the computer in this car or my previous 944 where I replaced the ABS ECU to fix a warning light...

Also wondering if there is some crude between the hub and sensor that is causing the light...

Hopefully a short drive up and down the road will sort it, it hasn't been further than a few feet for a very long time.