Alternator charging issues & blue exciter wire

[onZedge]

Here's something to try:

I just had my console and cluster gauge out to do some wiring modifications (and clean a bunch of connector contacts with Caig DeoxIT D100L). When I reconnected the cluster gauge to the harness, I turned on the ignition switch on just to verify the charge light was on - AND IT WASN'T!!

The little socket (that holds the charge light bulb) plugs into the back of he cluster and rotates to lock. Well, I had to rotate the socket to somewhere in between "full lock" and "full unlock" to get the charge light to come on reliably.

Perhaps this is the same issue that caused the PO to bypass the blue wire in the fist place?

[DeadPorsche944]

Originally Posted by onZedge

Here's something to try:

I just had my console and cluster gauge out to do some wiring modifications (and clean a bunch of connector contacts with Caig DeoxIT D100L). When I reconnected the cluster gauge to the harness, I turned on the ignition switch on just to verify the charge light was on - AND IT WASN'T!!

The little socket (that holds the charge light bulb) plugs into the back of he cluster and rotates to lock. Well, I had to rotate the socket to somewhere in between "full lock" and "full unlock" to get the charge light to come on reliably.

Perhaps this is the same issue that caused the PO to bypass the blue wire in the fist place?

The next time I pull the console I'll check it. Do you know if it is just a straight battery to bulb to alternator connection? Or is there a diode or other circuitry in the mix? I have not been able to find it on a schematic.

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[onZedge]

Battery > Ignition Switch > Ignition Switch Circuit 15 (switched 12 VDC) > Fuse Box > Instrument Cluster > Charge Light Bulb > 2-Pin Connector over the brake booster > Alternator Field Connection

You would only have to add a diode (cathode toward the Field Connection) if you have run-on issues when turning off the ignition switch (when using an MSD-6A for example).

Link to 924S Schematics below (should be almost identical to an early 944):

https://www.dropbox.com/s/tipsgc0alga5g6w/924S%20Schematics%20HQ.pdf?dl=0

[DeadPorsche944]

Originally Posted by onZedge

Battery > Ignition Switch > Ignition Switch Circuit 15 (switched 12 VDC) > Fuse Box > Instrument Cluster > Charge Light Bulb > 2-Pin Connector over the brake booster > Alternator Field Connection

You would only have to add a diode (cathode toward the Field Connection) if you have run-on issues when turning off the ignition switch (when using an MSD-6A for example).

Link to 924S Schematics below (should be almost identical to an early 944):

https://www.dropbox.com/s/tipsgc0alga5g6w/924S%20Schematics%20HQ.pdf?dl=0

I was getting run on conditions, but now that the battery is fully charged, it has stopped. I would just put the car in gear, step on the brake, and let out the clutch... Only had to do that twice.

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[Kar-ander]

This video explains how to bypass the instrument cluster and run your own wire using a diode https://www.youtube.com/watch?v=e9knTSJA1eo&t=6s

[onZedge]

Originally Posted by Kar-ander

This video explains how to bypass the instrument cluster and run your own wire using a diode https://www.youtube.com/watch?v=e9knTSJA1eo&t=6s

That's a band-aid hack - not a fix.

I bet a dollar that he never even checked to see if the charge light bulb burned out (which is an integral part of the charging circuit).