Quote:
Originally Posted by ponjohn
74 Ventura
Bone stock, 350 Pontiac 2bbl with AC.
OK...
- The atlernator light was on, naturally replaced the alternator. not charging
- Found the fuse blown for the "gauges"
- Replaced the fuse let it idle no issues.
- Took it for a ride a week later, no issues until...
- I accerlated like taking off from a light, alternator light comes back on, fuse blow.
- Today, I changed the fuse, verified it was charging 13.7v with DVM on Battery
- I gently went for a ride, probably not over 15 mph, no issue.
- Stop the car, hit the gas pedal as agressively taking off - bingo.
- Fuse blows.
- Measure voltage at battery 13.7 - appears to still be charging with the alternator light illuminated.
- Bring it back. change fuse, alternator light on.
- Let it sit for a 5 minutues, start it up alternator light off.
My theory:
1. Igition coil breaking down ( car sat for 10 years) and causing excessive current.
2. Movement of engine under hard load causing ground issues?
I am open to ideas or a better undertanding of the function of the alternator light. [ my understanding is, the guage fuse supplies voltage to "idiot" light which in turn provides excitement voltage for the alternator]
Thanks. |
The alternator light receives 12V from the ignition circuit through the printed circuit in the cluster. It grounds through the alternator when it is not spinning. When you start the vehicle 12V is fed back to the light from the alternator. When the light has both legs positive it won't turn on. If there is a difference in the voltage on either side of the bulb (e.g. Battery or alternator failure) the difference in the voltage will turn the light on. This is on an internal regulator style alternator. External regulator style works similar with the addition of the external regulator. Any kind or intermittent electrical issue ALWAYS go back to the basics. Good positive feed, good engine ground, and most importantly good body ground. I cannot tell you how many old cars(and new) I repaired by the addition of a good heavy body ground wire.