87 turbo low volts

[Raulg]

My 87 turbo keeps the needle to the bottom in the voltmeter upon start-up.
The car idles, but I need to rev the engine a few times up to 2000 RPM approx, then the needle in the volt meter will go to almost 14 volts and stay there.

If I shut the engine off and then re-start, it will do the same thing.

I replaced the alternator recently with a rebuilt one because of this condition, but the condition remains.
I re-tightened the alternator belt but it appears pretty tight, no slippage.
I checked the positive wires connecting at the underside of the fuse box, they were tight and clean.

I replaced the positive wire from the battery to the starter and the negative wire from the battery to the back of the engine a while ago since these wires had their insulation dry-rot and falling apart.

Has anyone had a similar condition? where else can I look for grounds or loose connections?
Thank you for your help.

[guru944]

Raulg:

That's a typical reading. Does your dome light dim significantly when at idle. Maybe you also have ground loop issues (subtle but present).
All the cars do. Use a Digital volt meter $10-20 from Harbor Freight or Sears to check all your ground points. Especially your 2ndary circuits, Horn, fog lights, tail lamps, cigarette lighter socket, dash lights, etc. Voltage should be 0.001vdc or less.
That is why grounding circuits (active/passive work when properly installed under the hood) and its noticeable and the 2-8hp dyno number reflect it as well. The 944 GND points are almost identical in all models. Later.

[Ronin-951]

Another thing that plagued the 44 line was that the exciter wire for the alternator was taken from the Gauge hook-up, and in line with the Low Voltage Warning Bulb, - lose the Bulb and you lose the exciter, so it takes rpm to pump up the juice. Have a careful look at the Gauge as you first Key On at the Bulb Check cycle. A Ballast Resister was added sometime in the series to cure this, but I have no idea when.

[87m491]

+1. Many Audi's and Porsches of the period need to goose the revs a bit before the alt starts charging. Feel free to check the exciter wire connection but sounds fine.