mark kibort

We think its a alterntor failure. I was able to stuff a huge Wallmart battery in my battery area and have enough voltage and current to run the car at all power settings. amp meter says, no charging happening. However, upon turning the key just before the starting position, something odd is happening.
It doesnt light up the red light at the bottom of the volt meter. however, the oil pressure light does come on. then, the exclamation light comes on along with the oil pressure light and they both start blinking. Ive never seen this!
then, with the key turned to start, using a good battery, it will start right up and run fin. (however, voltage is near the 10v mark, and still no red light )

could i have toasted my regulator on the alternator and this has broken some part of the circuit??????? could the brushes just be bad, but that doesnt make sense, because how would the system know something was wrong before the key is turned to the start position??

This is a puzzle i need answering soon!! I have a time trial to qualify for the import racer magazine even in November, at sears point this weekend!!!!

Let me know any thoughts on this one!

as a note, a long time ago, i was able to put a fluke meter in series with the battery and found that idling and running the 928 S4 takes about 10amps. it also needs about 11.5 min, to run well, and to start above 10 under starting load, otherwise it cranks over but doesnt fire. (but will jump-bump start)



MK

jon928se

Start from the begining.

Ignore the dash voltmeter at best it indicates high med or low.
Measure the battery voltage at rest using your Fluke meter or better if you can find an old fashioned AVO meter use that (say an hour after last engine running or last charge) - good battery that has been charged should be 12.5-12.8V. Then with the engine running use your Fluke to measure volts at both the battery and also at the jump post - should be 13.6-13.8V.

Then repeat the above test with the headlights on full beam and fog lights switched on and let us know the results you shouldn't see much voltage drop - around say 0.5v with the engine off and near none with the engine running. If you see the same voltage drop with the engine running you have a dud alternator. (Although dirty Earth points or +ve connections in the charge circuit could theoretically produce the same result) If the voltage isn't appreciably different engine running lights off versus engine running lights on then the alternator is probably OK, and then you have a more complicated problem to solve.

But as someone who has had a lot of experience with dead and dying batteries they do produce some strange effects when the volts get low.

HTH

Lizard928

to answer the question with the altenator,
the light for the altenator in the dash is probably burnt out.
replace the regulator on the back of the alt, cheap part and easy to replace brushes are on it too. If still doesnt work then you have other problems in the alt, such as a fried diode. And I would just replace the Alt.

the exclamation light and oil light will flash when the oil in the sump is low enough to activate the switch in the sump. This means you are down about 1.5 litres at a minimum.

Oldtee

Correct, check at the battery to see if it is charging. You only need 1/2 v above battery voltage. Go buy a digital volt meter ($30-50) you can plug into your cig lighter. Great diagnostic tool.

Jim bailey - 928 International

The red light is part of the exciter circuit and tells the alternator that it needs to make electricity BUT even without that circuit when you rev the engine the alternator usually will start charging. Odds are you have a bad voltage regulator (which includes the brushes) and that replacing it will put you back in business.

mark kibort

Thanks Jim! Do you have those in stock and are they pretty straight forward to replace.

Thanks for all the information folks. YES, i did all the prelim testing. I never use the gauge for on the dash for anything other than relative movement.

the values have always been 12.6 v for fully charged battery, when it starts to over in the 12.5 range, i know its time to change the battery (usually after 1-2 seasons.) with engine running , its always in the 13.8v range with fans on it can drop slightly . NOW, its running at 12.2 volts (battery nominal voltage, minus the voltage drop from the 10amp draw due to what it takes to actually run the car!) turn on the fans, it drops to 11.5 volts.

I think i mentioned, i bought a mongo battery from wall mart and ran on it in the race. it got the nominal voltage to 12.6 and under engine running load, it drops to 12.3 and it stayed above 12 volts all the way to the end of the race. I even was able to turn on the fans on the last few laps! the S4 doesnt run too well when the voltage drops to 11 volts! anyway, its something with the alternator, and certainly it sounds like a circuit is bad, due to the odd look of the dashboard lights just before the car is started. (ie flashing exclamation light and only a couple of the red warning lights come on)

any other thoughts. I need this thing running in a couple days if im going to make this qualifying for the Time Attack. This is a big, highly publizied event where they have NEVER had a 928 there. TV lots of magazine and web coverage. I dont want to try and make it using just a battery again. Plus i cant drive it to the track that way!

MK

IcemanG17

MK
You could drive to the track.....just bring a BUNCH of batteries with ya!! Plus a charger once you get there! I would remove the Alt and test it, since it doesn't take long and Intl could have a new one to ya in a couple days....might as well get the CLub Sport lighter one while you at it?

tommytomaso

should of drove it to NAPA and had them test the alt, and bat...
ofcourse on the trailer... would of made thier day..it not being a MINI VAN!!!

mark kibort

napa would have shaken the alternator to find this stuff coming out of it.
This pic shows the few rocks and racing rubber marbles that came out.
the two top pieces look to be part of a copper winding and possibly some kind of connection end point. the brushes looked good, but i dont know what new ones look like. they were about .75" long and the commutator looked like a commutator, with no obvious issues.

Mk

John Struthers

So the clean-out was the issue solver?
Or, did you replace the regulator and clean the chassis/Batt. ground?

FlyingDog

The rev to start charging sounds like mine. Is that the voltage regulator or some other failure?

mark kibort

the clean out showed me that there were some things that fell out that may be part of an internal broken connection. that little copper wire piece is mostly what i am concerned with. i cant rev the engine for the charging system to start engaging, after all, i was spending a good amount of time at near redline!
plus, the brushes look in pretty decent shape. (that regulator brushes compoent is two screws and it comes right off, and is self aligning. very cool)

MK

IcemanG17

MK
Did you take the alt down to get tested......

lorenolson888

Hi Mark,

I had mine tested two days ago at autozone (on Almaden) for free...

It took 3 minutes...

Loren

lorenolson888

Any update...

any verdict?

LO