rbonnett
09-09-2010, 07:23 PM
Background first: I have a 72 SIII petrol engine. Replaced the alternator about 9 months ago with a ProLine unit and also the battery at the same time. Had no problems up until about 3 weeks ago.
I stopped for fuel and couldn't turn over the starter. Got a jump start and ran home fine. When I got home, my meter showed a hair over 11 volts from the battery so I put it on the trickle charger overnight. Started fine the next morning and ran normally. I did put my booster box in the truck - good thing since the next day it wouldn't turn over again. Since then, I've needed the booster every time to get it started.
After a hiatus to get my broken shift lever repaired and get the truck back home again, I'm tackling this seeming charging issue.
With the engine running, I am seeing a peak of about 10 volts at the battery, slowly dropping the longer it runs. I'm kind of surprised it hasn't died - it seems to me like its running off the battery. Revving the engine was not changing the voltage reading - except to make it drop a bit faster.
So far I've replaced both battery cables, and cleaned up the connection for the ground when I did. When I pulled the connector from the alternator, the female connector were pretty corroded looking - got new connectors from NAPA and redid the connector block.
In the course of doing that, I noticed something odd - only 2 of the 3 outputs on the alternator had anything connected to them. There was no wire or connector at all for what I believe is the sensing connector on the alternator. I had noticed this at the time I replaced the alternator as well, but going by the wiring diagram in my Haynes book it didn't show a third wire - just the '+' going to the solenoid terminal and the warning light yellow/green wire.
Using the Green Bible, it looks like I have been missing the sensing wire all along. From the description there, not having the battery sensing wire working will make the alternator stop putting out the juice. Its really puzzling that it ever worked at all now that I've seen that - but I did measure around 14 volts at the battery when I installed the new one months ago.
I made up a new wire to run from the third output of the alternator over to the solenoid terminal - which is how I am reading the diagram in the GB. However, still no joy - same symptoms of slowly declining voltage with the engine running.
I have checked for drain with everything off - the meter shows zero current flowing so I don't think I've got a short somewhere.
So here's my questions:
- Is it possible that the alternator has been damaged from not having the sensing wire on it for so long?
- If I'm reading the GB correctly, how is it even possible it ever worked without one?
- Would charging the battery back up help at all? Right now its at about 10 volts or so with everything off.
Before I go yanking the alternator to take in for a test I want to eliminate other things that might be wrong that I can check at home.
Thanks in advance
I stopped for fuel and couldn't turn over the starter. Got a jump start and ran home fine. When I got home, my meter showed a hair over 11 volts from the battery so I put it on the trickle charger overnight. Started fine the next morning and ran normally. I did put my booster box in the truck - good thing since the next day it wouldn't turn over again. Since then, I've needed the booster every time to get it started.
After a hiatus to get my broken shift lever repaired and get the truck back home again, I'm tackling this seeming charging issue.
With the engine running, I am seeing a peak of about 10 volts at the battery, slowly dropping the longer it runs. I'm kind of surprised it hasn't died - it seems to me like its running off the battery. Revving the engine was not changing the voltage reading - except to make it drop a bit faster.
So far I've replaced both battery cables, and cleaned up the connection for the ground when I did. When I pulled the connector from the alternator, the female connector were pretty corroded looking - got new connectors from NAPA and redid the connector block.
In the course of doing that, I noticed something odd - only 2 of the 3 outputs on the alternator had anything connected to them. There was no wire or connector at all for what I believe is the sensing connector on the alternator. I had noticed this at the time I replaced the alternator as well, but going by the wiring diagram in my Haynes book it didn't show a third wire - just the '+' going to the solenoid terminal and the warning light yellow/green wire.
Using the Green Bible, it looks like I have been missing the sensing wire all along. From the description there, not having the battery sensing wire working will make the alternator stop putting out the juice. Its really puzzling that it ever worked at all now that I've seen that - but I did measure around 14 volts at the battery when I installed the new one months ago.
I made up a new wire to run from the third output of the alternator over to the solenoid terminal - which is how I am reading the diagram in the GB. However, still no joy - same symptoms of slowly declining voltage with the engine running.
I have checked for drain with everything off - the meter shows zero current flowing so I don't think I've got a short somewhere.
So here's my questions:
- Is it possible that the alternator has been damaged from not having the sensing wire on it for so long?
- If I'm reading the GB correctly, how is it even possible it ever worked without one?
- Would charging the battery back up help at all? Right now its at about 10 volts or so with everything off.
Before I go yanking the alternator to take in for a test I want to eliminate other things that might be wrong that I can check at home.
Thanks in advance