Disclaimer - only my guess:
Lead alloys seem to make better contact when carrying current, as seen in
car batteries with broken internal connections. I realize battery terminals
do the opposite because of powerful corrosive influences. Anyway, I suspect
the current creates a hot spot that effectively welds a small spot in the
connection and adjusts itself in size so that the connection stays slightly
below the melting point. When the current stops and the spot cools it is
prone to cracking, and something must change when the whole thing cools off
As I said, just a guess.
kindly indicate the model and age and mileage - it helps a lot in giving
you the advice you seek.
usually, if it dies while driving, it's the ignition switch - main
relays prevent starting, but not running, in my experience at any rate.
When you are driving,the interior is not as hot as when the car has been
closed up for awhile,and normal running vibrations keep the relay working.
No one here has ever reported having their main relay cut out their car -
while running-,only when it's been sitting,and more often in hot weather.
True enough, but just because no-one has reported it here doesn't mean it
couldn't happen, or hasn't happened. The fact is, the main relay energizes the
injectors, and thus COULD cause a problem with the car running. And if one is
counting on "vibrations" to "keep the relay working", I'd be very concerned
about vibrations keeping it FROM working normally as well - such a device in a
car should be virtually impervious to vibrations, period.
Then I shall be the first. Mine stalled in traffic years ago. The indications
are the main relay shuts down prior to rpm going to zero. Had no "fuel
pump" click from the relay when the car wouldn't restart. Most people
don't report their problem because most don't know for sure. And
most often, it happens only once in a blue moon.
One other note, this car never stalls in its 280k miles of lifetime.
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