Starter wont engage unless glow plugs are in plugged

[JeremyRobert]

I have a B2150 that the starter just clicks when the glow plugs are plugged in. When unplugged cranks just fine. I have replaced the ignition switch. No change. I do have voltage at the glow plug wire out of the switch when turned to crank. Did I get a bad switch or is there something else?

 

[LittleBittyBigJohn]

My gut reaction would be a weak battery. You could have enough voltage, and just enough amperage to do one or the other but not both. I've had batteries on the verge of bad do weird things, mostly in the motorcycle world. I'm pretty new to tractors.

 

[alexpops]

weak battery? dirty/corroded connections/cable to starter/bad ground? sounds like the battery isn't supplying enough volts/amps to run both starter & GP's at the same time. Try hooking up a booster/charger with decent amp output & try to start with GP's powered ... if that solves the problem, replace the battery or check your alternator output/other reasons you're draining the battery capacity.

 

[ljjhouser]

Weak battery is the first place I would also look.
I agree with sjstyles and alexpops.

 

[Roadworthy]

Watch your battery voltage while you attempt to crank the tractor. If it drops to eleven or perhaps 10.5 volts the battery is probably good enough but you could still have dirty connections at the battery or the point at which the ground connects to the frame. If the battery goes below about 10.5 it's time to replace it. They can generally hold a surface charge but may not have the current capacity to sustain voltage under load.