Compression Ignition Addict
Join Date: Dec 2007
Thanked 311 Times in 300 Posts
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Low Voltage wouldn't cause the relay to "stick" I don't think. The magnetic field, generated by the coil in that relay, would be weaker and less likely to hold-fast. If this happens only during a cold start (and Really cold starts, like without the benefit of being plugged-in on a frigid morning) would be when the current demands are the highest.
Bad contacts in the relay are then put to the test and is sounds like they're welding themselves together because of excessive heat (the solenoid on the starter wouldn't be able to do this if the relay had opened as it should because there wouldn't be any power available)
So, either the Ign SW is falsely holding the relay energized, OR the relay contacts are staying closed despite the SW opening the circuit to the coil and shutting down the electromagnetic field.
Next time, don't pull the Battery cable but disconnect either one of the sm wires on the relay. If it stops cranking, it's the sw (or sw circuit) if it doesn't it's the relay...