Branson 7845 blowing smoke

[LouNY]

You can see if the preheater is working, the light is on a temperature related timer,
it looks at coolant temperature and turns the heater circuit on.
It does not monitor the heater, that is located in the intake manifold and has a relay that sends power to the heater.
If you monitor the voltage and carefully feel the intake manifold close to the heater you will be able to feel if it's working.

 

[LouNY]

Your tractor is most likely pre tier 4.

 

[Number15]

Fresh fuel and injector cleaner would be my next step.

 

[LouNY]

You may want to check your air filters and air intake.

 

[DrericDO]

Definitely check your air filter. Not enough air and it will choke. Just remove the filter and let it run for a bit and if that doesn’t improve things then it’s not the filter. Next May want check the fuel filter and fuel separator. After that maybe try to adjust the fuel regulation into the injection pump. Too much fuel can cause black smoke.