main relay vs ignition switch while driving

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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 even more.
As I said, just a guess.
Mike
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snipped-for-privacy@gmail.com wrote:

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.
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jim beam wrote:

The main relay, IIRC, controls both starter and injectors... an intermittant one could most certainly affect running...
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wrote:

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.
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Jim Yanik
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Jim Yanik wrote:

-------------------------------
Precisely.
'Curly'
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Jim Yanik wrote:

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.
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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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Honda Accord '94, ~90K miles. I changed already the ignition switch!

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snipped-for-privacy@gmail.com wrote in

I resoldered the main relay on my 94 Integra GSR about 4 years ago,no problems since.(hot/humid central Florida)
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