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Voltage regulator wire cut - need advice

4K views 6 replies 5 participants last post by  Knorm65 
#1 ·
Hi everyone. I recently got my 70 GT on the street for the first time since I bought it. I had replaced most parts on the car, but not the alternator or voltage regulator.

I ordered a new regulator and when I went to replace it I noticed that one of the three wires which connect the alternator to the regulator were cut. I attached a picture, but I believe the cut wire to be the DF wire.

When driving the car everything seems to be okay and I actually have ~50 miles on the new engine. I read a bunch of posts on the forums here about the alternator / charging system and I found a nice wiring diagram but I am not sure why this would be cut or what purpose it serves.

Should I rewire it? Thoughts in general?

Thanks in advance for any help
 

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#2 · (Edited)
Opel GT Source (OPGTS) has voltage regulator harness, P/N 5017.

Edit:
OPGTS P/N 5055 alternator ground wire:


Diagram Parallel Electrical supply Drawing Technical drawing
Font Auto part
 
#3 ·
Hi everyone. I recently got my 70 GT on the street for the first time since I bought it. I had replaced most parts on the car, but not the alternator or voltage regulator.

I ordered a new regulator and when I went to replace it I noticed that one of the three wires which connect the alternator to the regulator were cut. I attached a picture, but I believe the cut wire to be the DF wire.

When driving the car everything seems to be okay and I actually have ~50 miles on the new engine. I read a bunch of posts on the forums here about the alternator / charging system and I found a nice wiring diagram but I am not sure why this would be cut or what purpose it serves.

Should I rewire it? Thoughts in general?

Thanks in advance for any help
The harness that Lindsay posted from Opel GT Source would be a good start. Or simply rebuild the existing harness with three new wires to new terminal ends (they come out of the connector by depressing the retainer tabs), connecting the same terminal at each end of the harness (the harness can be plugged in either way). Helps to use the correct colours for the next owner....

It looks to me that the field current wire (protected from the factory by a fusible link) that feeds energizing power to the alternator via the ammeter lamp has been cut off. The white remnants appear to be the fire-resistant sheath that normally covers the fusible link. That is just a piece of wire, 2 gauge smaller, that sacrificially melts when over-loaded. I replace the fusible links with in-line fuses, so if one blows, you aren't searching for a new fusible link and a way to install it (they are crimped from the factory and there are three fusible links in the harness)
 
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#4 · (Edited)
Opel used VR-124 voltage regulator.
OEM wire harness colors between alternator & voltage regulator (VR):
DF = Black D- = Brown D+ = Red

Short pigtail on VR Harness D+ (Red) connected to 12 GA Lt Blue w/ White strip wire with crimped fusible link wire (16 GA). This "Self-Excitation"/ "Boot Strapping" wire routes to small light bulb in AMP Gauge.

Bosch alternator is incapable of self-excitation, or "boot-strapping" itself to an operating condition.
Porsche 914 Alternator Troubleshooting | (1969-1976) | Pelican Parts DIY Maitenance Article

The voltage regulator "watches" the voltage at the D+ point, which should be the same as that applied to the battery. It now changes the short between the D+ and DF terminals into a variable resistance. This effectively controls the field current (whose source is now the output from the D+ terminal, and not the charge warning lamp) and thus regulates the output voltage of the alternator.

Edit:
Post #5 shows GT fusible link locations (including voltage regulator / alternator):
Opel GT Starting, Ignition, and Charging Diagram
 
#7 ·
You’ll have to show a photo of it. That black box is likely the little thing that cuts down on radio interference.
 
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