Put new honeywell gas valve on concord 80 plus unit. Came on and worked perfect, then checked for gas leak and had to tighten fittings up. Then went to kick unit back on and wouldn't work. Valve kept flashing 3 flashes for pressure switch or auxiliary limit stuck open. Took it back off after making sure there was no loose wire connections, made sure I hadn't got any dirt or small particles in any of fittings. Put gas valve back on still same code and not working. Noticed a crack in the gray plastic top covering of the honeywell gas valve. Could this crack be causing this issue with it suddenly not working and with the flashing code? I don't want to spend more money if this isn't the problem. Any ideas or solutions would be greatly appreciated. Thank You

Definitely yes. The cracked valve must be replaced as your pressure in the line is not what it should be and the furnace won't work properly without the correct pressure in the ine.

Thank you for your answer and I did replace with new honeywell gas valve and continue to get the 3 flashes for the pressure switch or auxiliary limit stuck open. Checked the orange rubber tubing no water or leaks found in it. The a/c running with no problem as does the fan when set to on. Any ideas would be greatly appreciated. Also followed the schematics and it shows it to be the violet wires.just not sure what to check next. Thanks