I had been noticing lately that my TR3 was not recharging the battery at
night, under load. It would do ok when there was not a significant load on
the system (like lights and driving lights) but it would go to discharge and
eventually the voltage would drop below 12 volts if I ran any time with a
big load.
The alternator was a nice chrome item I found at a hot rod swap meet several
years ago. It looked pretty cool, but I had no information as to its
condition or ultimate output. I knew the system worked fine when I first
installed it, but I have added a lot of load (like two big stereo amp,
driving lights, etc.) since then.
Well, I figured I must be getting up towards the maximum capacity of the
alternator. Not a problem, we'll just slip in a really heavy duty
alternator and solve that right now. Well, as with most things this ham
fisted amateur tries, that was much easier said than done, and in the
process I fried the VDO amp gauge that was in the dash. Of course, VDO no
longer makes my ammeter in the face that matches the rest of the gauges in
my dash so I ended up with a butt ugly white on black (green at night!)
generic ammeter. Oh, to mention burning up a second generic ammeter as
well! And spending much more time on this project than it deserved!
Well, after three evenings and $150 bucks, at least a half dozens calls to
the lists electrical guru, losing the cool chrome alternator and screwing up
the dash I still had the same problem! I found a local friend with a
battery load tester. Running through that routine and everything tested
fine, except the battery voltage was low and the alternator was not putting
out enough juice to charge it. OK, time to swallow the pride and go to a
commercial shop. I went back the local shop that had sold me the new
alternator and had them check it on the assumption that maybe the diodes had
fried during my tribulations with the amp gauge. When they put it on their
tester the diodes were fine, the alternator was fine and the battery,
although low on volts tested OK other wise. Finally while standing there
scratching our collective heads one of the mechanics asked if I had changed
the belt. Well, no, although a bit worn, the existing belt was tight and
appeared to turning the alternator just fine. He then suggested changing
the belt.
Bingo, the WHOLE problem was that the existing belt had "glazed over" and
although working fine at low load, when the alternator was under load it
would slip so bad that the alternator could not keep up with demand. All of
this work (and expense) could have been avoided by trying the simplest thing
first. It was entirely possible that just tightening that belt might have
solved the problem.
Lessons learned:
Don't assume that your first guess is right.
Diagnosis the problem BEFORE you start working on a presumed fix. Parts
swapping is no substitute for a real diagnosis.
Try the easy (inexpensive) stuff first.
Don't overlook the obvious
Ask for help before starting down the path and be willing switch paths when
the first one proves wrong
Anyone want to buy a really cool chrome alternator? :) Anybody got a NOS
VDO "Heritage Gold" ammeter for sale? :)
Kg
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