Mad Mackie
Lawn Addict
- Joined
- Jul 11, 2011
- Threads
- 50
- Messages
- 1,851
In my many years as a mech I preferred boats and aircraft as I found cars, trucks and heavy equipment not challenging enough to keep me interested. I have never seen an experienced auto mech that made the grade or had the patience to become a competent marine or aircraft mech. Several that I was involved with training had to be untrained and retrained which was a long and difficult process only to have them go back to their former situation where they made more money and were less accountable for their screw-ups.
Back to Scag,
If you follow the flow of electricity on your machines wiring diagram, you will see that there are many connections, terminals, switches, a solenoid, electronic control module, fuses and ground connections involved with just the engine cranking circuit. It all comes to sufficient battery voltage, good connections, good switches and a good ground to keep the electrical system functioning properly. In the cranking circuit, when there is a high resistance condition somewhere, the cranking relay is the weak point and it starts with intermittent cranking and then a failure of the relay.
The key switch supplies the power to the cranking relay when in the start position. If all the safety circuits are correct, the electronic control module which also needs power and a good ground to function, will ground the cranking relay which then allows power to the starter motor relay. The starter motor relay then provides high amperage power to the starter motor.
I have serviced machines that were two years old with 70 hours that had electrical problems. Many folks think that they can just shut off the engine in the fall and expect the machine to function in the spring without any thoughts to charging the battery and cleaning the battery terminals, let alone the fuel problems.
Back to Scag,
If you follow the flow of electricity on your machines wiring diagram, you will see that there are many connections, terminals, switches, a solenoid, electronic control module, fuses and ground connections involved with just the engine cranking circuit. It all comes to sufficient battery voltage, good connections, good switches and a good ground to keep the electrical system functioning properly. In the cranking circuit, when there is a high resistance condition somewhere, the cranking relay is the weak point and it starts with intermittent cranking and then a failure of the relay.
The key switch supplies the power to the cranking relay when in the start position. If all the safety circuits are correct, the electronic control module which also needs power and a good ground to function, will ground the cranking relay which then allows power to the starter motor relay. The starter motor relay then provides high amperage power to the starter motor.
I have serviced machines that were two years old with 70 hours that had electrical problems. Many folks think that they can just shut off the engine in the fall and expect the machine to function in the spring without any thoughts to charging the battery and cleaning the battery terminals, let alone the fuel problems.