Cod. error a04 on the display - Dishwashers

Make sure the printer is on and connected to the computer, either through your local network or a USB cable. Go to HP Customer Support - Software and Driver Downloads. If a Let's identify your product to get started page displays, click Printer, type your printer model number, and then click Submit. The software results page for your printer displays with the default operating system selected. If you need to change the version of Windows, click Change, select your version, and then click Change. Click Firmware, and then click Download. If a Firmware section is not listed, an update is not currently available for your printer. Save the file to your computer. Locate and then open the file to start the installation process.

it's c0291 (a 0 not an o)
you can chak for error codes at Datsc (http://datasc.com)
Here, you've the error lookup (Link)

It either has a short in the wiring or may need a new PCB

Comfort Zone heaters do not have a display board, they only had thermostat knobs.

Is it possible that you have a different model of heater?

System Error A04 indicates Timed out awaiting response from printer. To resolve problem, follow the instructions on this link: http://bit.ly/9ucEN8. If problem continues, I strongly suggest you contact Lexmark technical support to further investigate the problem. Thanks.

1. jQuery(document).ready(function(){ jQuery('#jsArticleStep1 span.image a:first').attr('href','http://i.ehow.com/images/a04/sq/7e/change-wireless-mouse-battery-1.1-800X800.jpg'); });
   Flip your mouse over and remove the battery cover. Gently pull it up and set it down in a safe place.
   
2. Step 2 jQuery(document).ready(function(){ jQuery('#jsArticleStep2 span.image a:first').attr('href','http://i.ehow.com/images/a04/sq/7e/change-wireless-mouse-battery-1.2-800X800.jpg'); }); Carefully remove each battery.
   
3. Step 3 Insert the new AA batteries into the mouse. Make sure the positive and negative connectors are lined up correctly. Do not force or jam your batteries into place.
   
4. Step 4 Place the battery cover over the opening and click it into place. Flip your mouse over. If your particular mouse has a charged or not-charged display light, make sure it is showing full strength.
   

you may have a bad heating element..or temperature sensor the water temperture is not getting hot enough to let the dishwasher run. you my reset it and try running the water in the sink until it reaches hot ... then try stating the dishwasher...let me know if this helps

buy a new printer