The problem is in the relay. In post #1, the s'driver is essentially shorting out the contacts inside the relay. Note that even with the contacts bridged, the current is still flows through the SAME wiring & connectors. So if it spins fast with the relay terminals bridged, then it cannot be these items causing the problem. The relay contacts maybe burnt from arcing or worn way. You can buy a 150 amp relay which comes as a black cube, only sligthly bigger than the popular Bosch 30 amp relay. This is what I use for the starter relay. 150 amps is waaaaaay more than the solenoid draws but it means the surface area of the contacts is greater, resulting in less arcing/wear.
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