NEVER STICK ANYTHING INTO YOUR PRINT HEAD!!!
With dampers disconnected, you can manually clean the print head using our desktop print head cleaning kit and PiezoFlush solution to gently flush out the print head micro-channels, then carefully wipe the bottom print head surface with a high quality Bounty paper towel and/or soft sponge tips (like these: http://www.amazon.com/Solvent-Cleaning-Sponge-Roland-Printer/dp/B00HT5AIYC).
It's always a good idea to thoroughly clean the printer when replacing parts such as dampers- clean the capping station, flushing box, wiper blade and print head by following our cleaning procedures: http://www.inkjetmall.com/tech/content.php?133-Printer-Cleaning-and-Preventative-Maintenance
By "readout plates" do you mean the cartridge chips? If the cartridges are correctly recognized by your printer when you push the back of the carts, then it may be an issue of the cartridge chips and printer's chip sensors not having a good connection. After reviewing your order history, I see you purchased the 4800 refillable carts about two years ago. When did you install these carts into your printer? I see you purchased replacement chips for the LM, LC and LLK positions, so assume those are the carts that are displaying errors- correct?
Please let me know so I can help resolve your cartridge errors.
Best regards~ Dana