In a message dated 97-07-01 08:07:10 EDT, jpudvin@us.ibm.com (Jay Pudvin)
writes:
> In hopes that someone has seen similar symptoms or could be kind enough to
> provide an educated SWAG. It's weird. Running at speed, the electrical
gauges
> (tach, fuel, h2oTemp) are fine. Hitting the brake, wipers, turn signals,
> knocks the gauges flat-out but only for a period of time (couple minutes?)
> before the gauges wake up again. Headlights and markers are not effected.
The
> horn does not produce an inturruption either. Before starting and w/
ignition
> on, signals and wipers work fine. Tips on diagnosing 'short' problems?
Could
> this be a hazard switch problem or perhaps voltage regulator?
Jay:
Just a wild guess, but it sounds like someone has mis-wired your car. Check
the voltage regulator for the gauges. You should have a dark Green wire(s) on
one terminal, and one Light Green wire on the other. My guess is some one has
added a Dark Green wire to the terminal with the Light green wire. If not,
look at the back of the gauges, and see if there is a dark Green wire
attached to one of the terminals where the Light Green wire terminates.
The voltage regulator is a thermal device. When current flows through it, it
heats up, causing a bi-metal strip to bend. There is a set of contacts
between this strip, and the output terminal. When the strip bends, the
contacts open, breaking current flow. As the heat element cools down, the
contacts close again, and current flows. During normal operation, these
contact open and close repeatedly, giving an average output voltage less than
the 12 volts applied. If the dark Green wire, which feeds the Brakes, wipers,
and Turn Signal is fed from the voltage regulator, it may be that the element
draws so much current that it gets so hot that it takes a long time to cool
off, and reclose the contacts.
If the dark Green wire were the only feed to the other items, they would go
out for the same period of time as the gauges, but it the dark Green wire is
in addition to the other dark Green wires, current would be split between
them till the regulator opened, then all the current would flow through the
other wire, and they would thus work as normal.
Your headlights, markers, and hazard circuits are not fed from the green
wire, so they would not have any effect.
It's a wild guess, but worth looking into. Right off hand, I can't think of
anything else.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition
'68 MGBGT---organ donor for the '74
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