No Alt Light...No Alt Voltage Reading

[OK-944]

I have a couple of alternator related questions that I could not quite answer by doing a forum search:

My 85.5's alternator check-light does not come on as I turn the key over.

After I start up the car, I see no voltage reading on the alternator gage, nor does the check light come on. Engine sounds fine, although I have not yet driven any distance to see if things remain ok, electricity-wise.

Does the 85.5 need a working alternator check-light to complete the charging circuit?

Anything else I could check before I go through the hassle of pulling the gage cluster yet again?

By the way, the alternator checked out OK at Autozone.

Another (related?) question: when I re-installed my starter, I attached the two large wires (one from battery, one from alternator) onto the large post of the starter, but with a nut between them and not mashed together as I've seen in photos. To my mind this should make no difference - because current is current and it should flow between the two wires despite the ends being separated by a nut. I had to install the wires this way as they were not angled properly to line up on the starter post without the second nut acting as a spacer between them. But perhaps I should try again to install them together?

Anything else I could check? Thanks!

[matthewb]

The "check light" does need to be good and completing the circut for the alternator to charge. At least that seems to be the experience I have had. There could be some other point in that circut that is bad though too. Check all the connections first then if you don't find the problem check the bulb and its connections.

[John_AZ]

The small "blue" wire from the alternator goes to the dash light. Check the curcuit. The wire may be frayed and is shorting. It could be disconnected in the dash area.

More info:
Starter & Alternator Troubleshooting

GL
John

[bell]

Does or did the car have a factory alarm? On the later cars the 2 wires which goto the bulb loop through the alarm brain......with non-alarm cars there are 2 jumper wires at the alarm plug to complete this circuit....
It is in the passenger footwell near the dme......
Again this is on later 944's, not sure on the earlier cars.

[mxfrank]

I've not owned the Porsche long enough to have had this problem, but most automotive charging systems of this era used the dash light to provide boostrap current to the alternator. If the bulb fails, then the alternator won't be able to charge. I like to wire a 330 ohm resistor in parallel with the bulb if this is the case. That way, a failed bulb won't cause the charging circuit to fail.

On the starter question, you are correct...current is current. If you need to separate the wires, your solution is fine.