944s Alternator power

RaceProjects · 01-03-2004, 03:41 AM

Hello,

I'm new on this forum and already coming with a question.
What power has to be indicated on the dashboard Volt meter when the car is running ?
On our BMW racecars we always had 14.4 Volts ( with the engine running ) but on the Porsche it stoppes at about 13 Volts.
Now that it has become a bit colder here in Belgium the battery has gone death for the second time.
The wiring has be checked and there is nothing wrong.
I can jumpstart the car again but after one cold night it is death again.
Is my alternator gone ???

bearone2 · 11:47 AM

should be 13.7 running. more than likely the voltage regulator/brush assembly. brushes could be worn.

SoCal Driver · SoCal Driver's Garage

Clean the grounds on the back of the engine to the chassis and to the battery. Also clean the positive cable including the three wires that clamp under the bolt.

Zero10 · 01-03-2004, 11:18 AM

If you are referring to the gauge on the dashboard, mine reads 12V, however it is rare that this gauge will read accurately. So if yours reads 13V check at the battery with a voltmeter.

The charging voltage should be between 13.5V and 14V.

ronin · 01-03-2004, 11:31 AM

your battery sounds like it might be on its way to failing. follow SoCal and Zero's recommendations, if you get 13.5 to 14 charging volts (with engine running) on a multimeter at the posts but the battery still wears down after a cold night, then the battery is most likely the culprit

bearone2 · 01-03-2004, 11:48 AM

also check that the alternator lite comes on when you turn on the key.

IceShark · 01-03-2004, 12:39 PM

Well, you are in Belgium so it isn't that cold. COLD is when you hit minus 50*F. Then everything goes to hell in a handbasket.

I suspect the top items to look at are the battery, a drain on the battery when everything is shut off, wire terminal connections for corrosion and the alternator. The Bosch alternator uses a stock voltage regulator that is set at ~ 14.0 to 14.1 volts and should be replaced with an adjustable voltage regulator set up around 14.4 volts or a bit higher. You can get one in Europe from Transpo, German based, - the IB373A. If it is expensive or hard to find I can send one over to you for about $24 USD including the shipping. Send me your postal code and I can figure out exactly what the shipping would be.

Cleaning up the battery cables can do wonders but Porsche used bare copper terminals which were just crimped on to the wire core. What happens is that corrosion walks up the interface between the terminal and wire. You are basically screwed then and have to replace the cables. I also sell some upgraded battery cables but those might be a bit expensive to ship to Europe due to the weight.

The other problem is the fuse/relay board. That leaks voltage all over the place and there is not much that is simple you can do about fixing it. I sell a supplemental positive for the run over to the fuse/relay board but still only get ~ 14.0 volts to the interior voltage gauge when the alternator is putting out 14.4 volts.

Good voltage is a Porsche curse that takes quite a bit of work to solve.

MrPants · 01-04-2004, 02:11 AM

what is the link for your website iceshark?
i used to have it but now its gone

IceShark · 01-04-2004, 08:01 AM

MrPants, you are probably thinking about Danno's GuruRacing site at http://www.gururacing.net/

Then you click on the left on lighting. I really didn't have anything to do with that - Danno and Ben S. did it because they liked the lighting stuff I sold them. Danno asked if he could put it up and I said OK, fine. I just do this as a sideline hobby.

If you want to see more pictures of the headlight package as well as the battery cables you have to go to Rennlist and do a search. There are a lot of pictures posted. Those links on the GuruRacing page that went back to the Rennlist threads are now broken and don't work because Rennlist did some "upgrades" and smoked the old threads. There is not a lot I can do about fixing that as I am a computer idiot and Danno is doing me a favor having that page up in the first place and I really can't order him to spend a day fixing it all up.

RaceProjects · 01-04-2004, 01:57 PM

Quote:

Originally posted by IceShark
Well, you are in Belgium so it isn't that cold. COLD is when you hit minus 50*F. Then everything goes to hell in a handbasket.

OK, it isn't that cold.
But we aren't that well adapted

BTW, I installed another battery and the problem seems to be solved.
I check the voltage with a multimeter ( at the battery ) and it does read 13.5 Volt at a very steady rate.
When I start to defrost the rear windows it goes down to 13 V but that should be normal I think.
Anyway, thank You all for the good advice.
Although the problem is solved I am still going to check the connections on the engine and the cables to the battery and alternator.
That way I can avoid having this problem in the future

IceShark · 02:38 PM

Good you solved your major problem with the battery. Which I'm sure was caused by the low charging rate of the Bosch alternator.

Until I stumbled axross this voltage regulator issue, I couldn't keep my battery at full charge unless I went on a trip that lasted 10 hours.

Check with your local alternator/starter shops and see if they can get the higher output regulator I mentioned.

You should be seeing more like 13.9v or more at the battery once you get things squared away and fixed. I'm concerned you will ruin your new battery in a year or two from undercharging.