Quote:
Originally Posted by Xsbank
That diagram doesn’t make any sense to me - what’s the point of that other, smaller solenoid?
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Actually, this additional relay/solenoid in starter circuits is very common. It has many names: aux. mag. switch, aux. starter relay, remote starter relay, Ford solenoid and others. Its purpose is to provide more current to the starter solenoid.
With this relay installed, a very small current from the starter/ignition switch contacts can activate the starter solenoid, which on larger starters can be substantial.
Here is a Perkins wiring diagram that shows the relay as an 'optional relay'.
A fuse or circuit breaker when fitted will be located somewhere between the battery and the ignition switch. Cummins B-Series diesels I have owned had 10A engine-mounted breakers, and were referenced in the troubleshooting section of the owners manuals relating to starting.
I agree with other posters, check the circuit breaker as they can definitely fail and become 'weaker' with age.