Hp deskjet 920c-printing problems

[pmf]

My printer behaves as if it is printing normally, it feeds paper, the ink carriage traverses as if printing, and there are no warning lights. I can hear ink sloshing about in the black cartridge when I shake it, but no ink appears on the paper. The colour cartridge is empty, but the printer is set to print in black only. What next?

 

[hang-the-9]

Replace both cartridges, should print fine unless your print heads are bad. Odd that there are no lights or errors coming up due to the empty color cartridge, it should not even try to print like that.