In Reply to: 1940 9N starter relay question posted by Serge on January 22, 2018 at 18:44:29:
"on my 9n there is no click when trying to start the engine If I clean everything and still no clcik does it mean the relay have to be replace?
NOTE: also does the relay have something to do about keeping the engine running??
the fact the push starter switch is not working if I use some booster cable connect the + on the starter and + battery and the - at the - battery use the other end of the - touch the tractor frame. The engine turn and it's trying to start (I keep playing with the choke and play with the gas when it seems to start if I let go the - from the frame it does not keep runnig."
First, it has a switch not a relay:-) The switch has two large terminals. One terminal has a cable which connects to the battery, the other has a cable which connects to the starter. There is another wire which goes to (or through) the ammeter (depending which type of ammeter you have). That wire supplies power to the ignition, lights, and also supplies charge to the battery from the generator or alternator as the case may be. That wire goes on the same terminal as the cable that goes to the battery. If it is on the terminal that goes to the starter, then when cranking the engine will fire, or "try to start", but as soon as the switch is disconnected the engine will die.
In another post you said that you had something like 3.5Ω across the switch when you checked it with a meter. If the plunger was fully depressed when you made that check, then yes, the switch needs to be replaced. Sometimes the linkage from the starter button by the gearshift to the switch gets worn and will not depress the starter switch fully. This will cause the switch to not make contact, or to make the switch arc inside burning it up.