Alt/Volt Reg Help

techguy · 06-29-2004, 06:57 PM

Help!

Here is the situation, 72 Targa with a 75S Motor in it.

Within the last year the tach has bounced above 3000 RPM like crazy, voltage at battery at idle is about 12.5V with the headlights, radio, and turn signals on. I just noticed tonight that the turn signal indicators both flash when turning left or right only at idle, when I apply a bit of gas or turn off radio and lights and they flash normally. I know the signals will act like this with a bad ground and I had this problem when I bought the car but cleaning all the bulb sockets and installing a new turn signal switch solved the problem.

I have read several posts and believe the problem is the volt reg or alt on its way out. I also see in Wayne's book that ext volt regulators are std up to 1981 and several people upgrade their alts to an internal volt reg.

My Questions:

1) Thoughts on volt and alt as the problem?

2) What is going on with this panel? Do I have an internal or ext volt reg? I suspect someone has maybe added some of the 75s wiring in?

Randy Webb · 06-29-2004, 07:32 PM

Does it say 'Marchal' on it? If so, that's the est. V. reg. I'm not sure what year they went to internal -- definitely by 1986. You may need to measure voltages with the car running.

Also, did you check and clean or replace your points? That will also cause the bouncing.

techguy · 06-29-2004, 07:37 PM

Thanks Randy,

I will pull the alt tomorrow and start tracing wires, may be my only option. The points were changed last year with the Permatune. I thought the Bosch CDI died so I bought a Permatune and coil from a guy in the PCA club...it turned out the points fried and the coil was weak. I left the Permatune and the new coil in with a new set of points. Could be both the alt and the points?

LakeCleElum · 06-29-2004, 08:06 PM

TechGuy: I just replaced a VR that looked just like this one in my '73.5T. It's a Bosch although it doesn't say that on the unit. I bought one off the internet for about $35. Be glad it's not a Marchal; they listed for about $105. If I was you, I'd pull the Alt and take it to a "Auto-Electric" shop and have it tested 1st. Could just need brushes. Most will rebuild it (with new diodes) for between $75-100.....Good luck...Bob S.

techguy · 06-30-2004, 07:34 AM

Looks like the alternator is a Marchal and the voltage reg is a Bosch mechanical unit. I am going to the auto electric shop now for a test.

What are my options?

LakeCleElum · 06-30-2004, 12:57 PM

If the Alt. tests OK, I'd ask the shop to if they can test the VR. If they can't, it's only about $35. I'd start there. While pulling the Alt, I'd check for corrorded connections around the 14-pin connector, the Blue wire to the Alt., VR connections and make sure the bulb is good in the dash....Good luck...

techguy · 03:45 PM

Looks like the bearings are toast in the alt, I did not even bother with a bench test as a result. I am having the alt rebuilt and will upgrade from the mechanical to newer electronic (ext) regulator. In addition I just spent 2 hrs removing the crud from the fan and housing. I'll post some pics when then start to get back together.