Cause of error code A06

Safety Circuit is open.

Solution for error code A06

1. Error shows when safety circuit is open. Remove J13 connector from control module. Check for continuity between two pins connected to two pink wires, is continuity available?
Yes: Replace control module
No: -> 2

2. Unplug molex connector on supply temperature sensor. Check continuity between two pins on sensor (two pins connected to two pink wires) . Is continuity available?
Yes: -> 3
No: -> 4

3. Check for loose connections on two pink wires on J13 connector, supply sensor, and safety temperature switch. 
Yes: Fix loose connections 
No: Replace wire harness

4. Is boiler supply pipe (above heat exchanger) hot?
Yes: -> 5
No: -> 6

5.  Let all zones run until water temperature drops.
Boiler fired without enough water flow through heat exchanger. Heat exchanger is over heated. Either high limit or heat exchanger temperature switch is open.
Check the following: Air in system? Verify water flow in system piping. Flush system if water is dirty. 

6. Is Heat Exchanger surface hot?
Yes: Wait for boiler to cool down.
No: Check high limit and surface temperature switches. Replace Broken Switch