Bob. thank you for your reply. I got busy after receiving your reply and have only just followed your instructions.
The printer is an HP Officejet 5110 al-in-one but I have only ever used it for copying. It has worked well up to earlier this week and although it often showed on the LCD screen "Check colour cartridge" it seemed to over-ride that when I press "copy" and adjusted the options before pressing "Black" under "start". I even put in a new black cartridge in May, 2018, without any problems. I put a new colour cartridge in the printer in October, 2014, but rarely used colour printing so when the error message for the colour cartridge came up I ignored it and it worked OK as above.
This time, I tried to copy some black text documents. It copied one OK but then would it would not print a second. There was no error message for the black cartridge but as I last changed it in May, 2018, I guessed it must be empty. I had a new black cartridge so replaced it and then it would not print, still displaying the "check colour cartridge" message.
I cleaned the contacts as you suggest although it is difficult to reach the contacts in the machine! But I think I did them OK. I put the colour cartridge back and after the cartridge had gone back to its position the LCD screen was showing "Remove and check colour cartridge". I pressed "copy" and "Number of copies 1" started to flash. I pressed "options" and scrolled down to the "lighter/darker" option and adjusted it to a light printing. I then pressed "Black" under start. The item to be copied goes into the machine but it immediately flashes "Check colour cartridge" and it does not print the copy.
It is annoying that all did was to change the black cartridge and it stopped working!!
Any further suggestions will be gratefully received.
Would it help if I put in a new colour cartridge? I have not got on so would have to order one.
Is there no way to override the "check colour cartridge" message?
Thank you for your help. Richard Camp, Telford, England.