I sprayed dust remover & now the printer won't print. the status light flashes red & the toner, drum & paper lights flashes yellow (hl5250dn)

Try this Toner reset sequence (worked on Brother HL-5350DN)
With Printer off open the toner door
Hold the Go button as you turn the printer on.
All lights will turn on. Keep holding Go until status light goes off.
Press the Go button 2x.
The Paper, Drum & Toner light will come on
Press Go 6x
Status light will turn red
Close the front.

Well, if the toner light is on, you're probably out of toner and the only reason it ran, was because it was low but not completely depleted.

Try new toner drum off of Ebay or Amazon for the best prices for your brother printer.

A solid red STATUS light with a solid yellow TONER light indicates toner out...replace according to pg. 63 in the manual.
It can also indicate a cartridge position error. Take the DRUM UNIT out of the machine and re-install.

A solid red STATUS light only means:

Front cover open
Fuser cover open
Dust on drum
Too many trays
Buffer error
Print overrun
Memory full
Download full
Font full

See pg.48 ofthe manual.

When all lights flash it's a service problem. You press and hold the go button and see what lights are on then.error light means main PCB failure, Toner light means fuser failure, drum light means laser failure. Toner and error light means main motor error, drum plus error light means its a fan failure.

change your yellow toner insert new toner cartridge then solve your problem

The red lite indicates one of the following needs to be looked at:

Cover open (Front cover) Close the front cover.

Cover open (Jam clear cover) Close the jam clear cover of the fuser unit.

Memory full - Press the go button.

Print overrun - Press the go button.

Clean drum unit - Clean the corona wire.

f the Drum LED is still lit after replacing the drum unit, the Drum counter may not be reset.
Reset the Drum counter as follows:

1. Open the front cover.
2. Locate the control panel button under the LED lights on the left side.
3. Press the control panel button until all lights are lit, then release it.
   The Drum counter is now reset.