Viessmann KK10 Installation, Start-Up And Service Instructions Manual page 19

Diagnostics
(for qualified service personnel only)
Electrical connections and sequence of operation
Using a volt-ohm meter, place one probe onto neutral test point terminal (TPN).
Use the remaining probe to touch the individual test points to diagnose the
problem. Follow the steps below through the individual test points.
Test point 1
Is 120 VAC present?
No Check main 6.3A fuse and replace as necessary. Retest.
Yes Continue with Test point 2.
Test point 2
Is 120 VAC present?
No FHL has tripped. Reset and ensure pump(s) is/are operating.
Yes Continue with Test point 3.
Test point 3
Is 120 VAC present?
No Power flow is not returning from burner. Check burner plug.
Yes Continue with Test point 4.
Test point 4
Is 120 VAC present?
No AHL has tripped. Allow boiler to cool and restart.
Yes Continue with Test point 5.
Test point 5
Is 120 VAC present?
No Contact 1K1 possible not closed.
Test burner operation using FHL test.
Check room thermostat circuit.
Yes Burner operation is required at this point.
Service burner.
Top view of main circuit board
Back of control
Front of control
Troubleshooting
19