Early 911 Electrical Issues
01-17-2002, 10:58 AM
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Early 911 Electrical Issues
Ladies and Gentlemen:
Before I ask a few questions regarding some electrical troubleshooting I am reminded of Edgar Allan Poe's famous line, "Should you ever be drowned or hung, be sure and make note of your sensations."
With that out of the way, here's the situation: I have a 1971 T with an "E" motor that is having some electrical charging issues. The alternator light DOES NOT LIGHT when I turn the igniton on. I put my digital VOM on the battery terminals with the engine running at 3000 rpm and got 12.5 volts, suggesting either bad wiring, a bad alternator bulb, bad regulator or bad alternator. I checked the bulb and it's OK, verified continuity of the blue wire which runs through the bulb--terminal #11 of the 14-pin connector on the rear of the "console" -- and the wires leading into the shroud. I have +12v to the other side of the bulb through the red wire with black stripe.
Now the fun starts: this car doesn't HAVE an external voltage regulator-- it has been removed from the "console" and replaced with an MSD 8910 tach adapter (which looks like the transformer from a doorbell). And yet, through the hole in the shroud run five wires: a large red (B+ from starter), a medium brown (D- from ground through hot-start relay), a smaller red (B+, to hot-start relay #51), a small blue (D+/61, field current from the warning light) and a medium black wire (DF, which runs to the "console" and presumably goes nowhere).
And now, at last, the QUESTIONS:
1. How can I test the voltage regulator without pulling the shroud? I suppose I could jump the blue wire (D+/61) to +12v which would energize the field and cause the alternator to go to maxium output, which would then be reduced by the internal regulator.
2. I suppose it's possible that the engine installers put an externally regulated alternator in the car, WITHOUT installing an external regulator. This would seem to explain the FIVE wires running through the hole in the shroud instead of the THREE required for an internally regulated alternator. Any way to check this, short of pulling the fan and looking at the back of the alternator?
Ok, see my related posts for the Story of the Smoking Dashboard,and the Abandoned Wire Mystery. Not exactly Poe, I'll admit. Thanks in advance for any advice I can use over the long weekend.
John
'88 Carrera 3.2
'71 E (PCA H Stock)
Before I ask a few questions regarding some electrical troubleshooting I am reminded of Edgar Allan Poe's famous line, "Should you ever be drowned or hung, be sure and make note of your sensations."
With that out of the way, here's the situation: I have a 1971 T with an "E" motor that is having some electrical charging issues. The alternator light DOES NOT LIGHT when I turn the igniton on. I put my digital VOM on the battery terminals with the engine running at 3000 rpm and got 12.5 volts, suggesting either bad wiring, a bad alternator bulb, bad regulator or bad alternator. I checked the bulb and it's OK, verified continuity of the blue wire which runs through the bulb--terminal #11 of the 14-pin connector on the rear of the "console" -- and the wires leading into the shroud. I have +12v to the other side of the bulb through the red wire with black stripe.
Now the fun starts: this car doesn't HAVE an external voltage regulator-- it has been removed from the "console" and replaced with an MSD 8910 tach adapter (which looks like the transformer from a doorbell). And yet, through the hole in the shroud run five wires: a large red (B+ from starter), a medium brown (D- from ground through hot-start relay), a smaller red (B+, to hot-start relay #51), a small blue (D+/61, field current from the warning light) and a medium black wire (DF, which runs to the "console" and presumably goes nowhere).
And now, at last, the QUESTIONS:
1. How can I test the voltage regulator without pulling the shroud? I suppose I could jump the blue wire (D+/61) to +12v which would energize the field and cause the alternator to go to maxium output, which would then be reduced by the internal regulator.
2. I suppose it's possible that the engine installers put an externally regulated alternator in the car, WITHOUT installing an external regulator. This would seem to explain the FIVE wires running through the hole in the shroud instead of the THREE required for an internally regulated alternator. Any way to check this, short of pulling the fan and looking at the back of the alternator?
Ok, see my related posts for the Story of the Smoking Dashboard,and the Abandoned Wire Mystery. Not exactly Poe, I'll admit. Thanks in advance for any advice I can use over the long weekend.
John
'88 Carrera 3.2
'71 E (PCA H Stock)
