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tj924 · Posted: Sat Oct 30, 2004 9:57 pm Post subject: Battery still not charging

My battery still isn't charging

. Was 12.2 before firing up & dropped to 11.6ish when started. Reving the engine made no difference & turning on various accessories (light fan etc) dropped it further to around 11.3.

I have just had the alternator out & replaced the voltage regulator. I noticed that when I turn the key to "Start" before cranking it, the alternator light does NOT come on at all. Am I to understand that I am probably looking at a problem with the D+ wire or possible a blown light bulb. Any tips on troubleshooting?

If the D+ wire needs to be replaced (looks OK at a glance, but it runs most of the way that I can see it inside a black tube along with some other wires), what it the best way to re-run it through the firewall?
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TJ
Silver '82 924 NA 5-Speed Manual

924RACR · Posted: Sat Oct 30, 2004 10:35 pm Post subject:

I'd definitely be suspicious of the wiring from the alternator and the gauge reading... also the ground for the gauge. Before you tear up the wiring, use a voltmeter and doublecheck the measurement at the gauge - both to a hard ground and to the gauge ground. There is usually an inadequate ground for the dash in these cars, which is why I recommend adding one.

It's also possible that you have a poor or no connection in the connector that plugs the alternator into the rest of the car. On US cars it's a 3-pin white nylon plug on the firewall at th back of the cam cover; don't know 100% that it's the same on RHD, but I would assume so. These contacts can get worn, weak, or corroded, preventing charge from getting to the car.

HTH...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

tj924 · Posted: Sun Oct 31, 2004 12:00 am Post subject:

So the D+ wire effectively goes from the light through the 3-pin white nylon plug on the firewall at th back of the cam cover & down to the alternator? Anything else plugged into that connector?

How do I check the measurement at the guage? Is it easy to check the bulb?
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TJ
Silver '82 924 NA 5-Speed Manual

Smoothie · Posted: Sun Oct 31, 2004 12:46 am Post subject:

Possibly the quickest way to check if the problem's with the exciter wire/bulb. Run a jumper wire from D+ to ground and turn the ignition on, but not to start. If you get the dash light, you know the wire and bulb are ok.
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"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

tj924 · Posted: Sun Oct 31, 2004 2:05 am Post subject:

Traced the conduit into which both the B+ & D+ wires disappear & found the 3-pin white nylon plug that 924RACR is talking about. On my car it is (looking from the front of the car) on the top right-hand side of the engine bay near the battery. That is actually the opposite side of the engine bay to the cam cover.

Pulled it apart & it looks OK at a cursory glance. Any way to clean the contacts in there?

Smoothie, there is a ground wire that runs from a bolt that holds the cover on the alternator to the top bracket that holds the alternator on the engine block. Should I just temporarily connect this wire to D+ for testing or should I connect a new (temporary) wire?

How do I get to the bulb for the alternator warning light?
_________________
TJ
Silver '82 924 NA 5-Speed Manual

Smoothie · Posted: Sun Oct 31, 2004 4:39 am Post subject:

It doesn't matter how you run D+ to ground. Could do what you mentioned, could disconnect the exciter wire from D+ and run the wire to ground, whatever's easiest. I was thinking a seperate wire would be easiest.

Whether that makes the light come on or not, next you could run a wire from batt 12V(+) (or from 12V(+) anywhere), run that to D+, start the car and check to see if that starts the alternator charging.

To get to the alt light bulb, you have to remove the gauge. The gauges push out from behind the large plastic bezel that they're mounted in.
Look here - http://www.924board.org/viewtopic.php?t=13104
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

tj924 · Posted: Sun Oct 31, 2004 10:19 pm Post subject:

Testing so far gives the following results:

Car off

Battery - 11.86v
Alternator B+ - 11.85v
Alternator D+ - 0.00v

Ignition turned to the start position just before cranking (oil, park brake & brake lights on, alternator light off)

Battery - 11.52v
Alternator B+ - 11.48v
Alternator D+ - 10.98v

Note that I checked by putting the volt meter's -ve lead on the ground strap bolt on the alternator itself & on the ground strap bolt on the engine & get the same reading. That says to me that the ground strap itself is OK & I have a good ground connection there.

Disconnected the D+ wire & the ground strap from the alternator & joined these 2 wires together (both have ring connectors & I just put a bolt through them). Turned the ignition on & the alternator light now comes on!

So, I now know that the dash light & D+ wire are OK & I get close to battery voltage at the B+ wire, so battery to starter to alternator is OK. Is that correct?

I've replaced the voltage regulator, though not with a genuine one ($90+ vs $20) & I did notice it's ground connector was on the opposite side to the genuine one. Would that make a difference?

What the heck do I check next???
_________________
TJ
Silver '82 924 NA 5-Speed Manual

Paul · Posted: Mon Nov 01, 2004 12:59 am Post subject:

Disconnect the D+ wire and tell us what the resistance is from the D+ post on the alternator to a ground point on the alternator.

tj924 · Posted: Mon Nov 01, 2004 2:00 am Post subject:

Joes924Racer · Posted: Mon Nov 01, 2004 2:11 am Post subject:

The alts grounded and has an exciter wire ??
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

tj924 · Posted: Mon Nov 01, 2004 2:16 am Post subject:

If I understand your question correctly Joe, then yes, the alternator is grounded & has an exciter (D+) wire. With the D+ wire connected I put a 2nd ground strap from D+ to the alternator ground point on the engine. The alternator light now comes on when the ignition is turned to start, but stays on even with the engine running. Without this 2nd ground wire the alternator light never comes on.
_________________
TJ
Silver '82 924 NA 5-Speed Manual

Smoothie · Posted: Mon Nov 01, 2004 2:39 am Post subject:

Joes924Racer · Posted: Mon Nov 01, 2004 2:47 am Post subject:

Hey TJ924 did you have the alt tested to make sure its good.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Sleykin · Posted: Mon Nov 01, 2004 3:19 am Post subject:

The 2 ohm difference concerns me. In a charging circuit (or starting circuit) 2 ohms is a LOT of resistance. I would fix the ground from the alternator to the block to the battery.

Paul · Posted: Mon Nov 01, 2004 6:59 am Post subject:

Time for a new alternator. Some places will test it for free if you would like a second opinion.