After doing the brakes mentioned in an earlier post I moved on to installing a
new voltage stabilizer (VS). This is the little device that sends reduced
voltage to the instruments on most LBCs(or even Big British Trucks, such as
Land Rovers and Range Rovers). When I was testing the electrics on my 69 MGB
project the #2 fuse would blow immediately when the key was turned on with the
GLG wire (from the "I" terminal to the gauges) attached to the VS. I tested
the old VS and concluded that it was shorted inside, and was bad out of the
box. So, when a new one arrived I tested it as described by Mr. Twist. With
the power to "B" terminal, and the case of the VS grounded, a test light
between the "I" terminal and ground will flash slowly as the thermal resistor
inside heats, expands, contracts (On, off) etc. like a slow flasher.
It tested good, was installed, and immediately blew a fuse. With the GLG
removed, and a new fuse, no problems (as evidenced by the fan working with the
key on). By a process of elimination (and another fuse later) it turns out
that the temp gauge was shorting direcly fom the GLG terminal to the case and
thence to ground. Of course, this is the hardest one to reach. Apparently the
PO (they always do it, dont they?) had cleaned the gauge and was not careful
on reassembly. The two terminal posts must not touch the case, or it will
short out. The case is grounded only to provide a ground for the instrument
light, not the guage itself (which is suposed to be grounded by the sending
unit). I removed and reassembled it, and now all is bliss. Moral: Never assume
that the other guy did it right, suspect anything that you didnt personally
do. This is probably a little harsh, since most of what the PO did is actaully
pretty good as it turns out, but.....Cheers, Andy Blackley
|