The Prince of Darkness strikes during daylight...
On my morning commute, I noticed that my tach, temperature and fuel
gauges went out. (Oil pressure gauge still on). I stopped at an appt. for
about 20 minutes and went I came back out and fired up, everything was
working the rest of the way in to work.
Is this my voltage stabilizer getting ready to die? What would
cause it to become temporarily unstable? Or is there something else
going on?
This is a 74 MGB.
On my '74 Midget, I used to have the same problem -- tach would drop to
zero, and at least one of the other gauges would slowly creep toward the
bottom of the dial as well. (I think it was in fact the fuel and temp
but this was almost ten years ago.) In my case, the problem was that
the brass spring clips that held in the fuse for that circuit -- they
were all on one circuit -- had weakened to the point that the fuse could
shake out of their grip and the circuit went open. This only happened
for me on fairly bumpy or twisty roads, and the time I particularly recall
was on Old Topanga Canyon, which Southern California residents will agree
is heavy on both.
To solve this, I took the fuses out, polished the metal on the connectors,
then pinched them closer together to restore the spring tension on them.
I also replaced all the fuses on general principles. I never had another
fusebox related problem on that car. (Just don't ask me about the
brake lights... :-)
Speaking of fuses, don't forget that a fuse can occasionally fail due to
a manufacturing defect. I've seen one or two of these thirty-five-cent
fuses fail when one end of the metal strip became detached from the bullets
at the end of the fuse, but it wasn't obvious to a cursory inspection.
If a blown fuse could solve the problem -- that is, if the problem affects
all the electrical devices on a single ciruit -- *always* swap in a known
good fuse before doing any more troubleshooting. If it solves the problem,
then peer down the inside of the fuse you took out and see if it's bad.
You might be surprised -- and you'll definitely be relieved that you
don't have to pull all the wires to look for open circuits elsewhere in
the guts of the system.
--Scott
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