Google for Honeywell_SV9641M4510_Installation.pdf
The SV9540; SV9640 SmartValve™ System Controls
combine gas flow control and electronic intermittent pilot
sequencing functions into a single unit. The low voltage
igniter, flame sensor and pilot burner are supplied by the
Q3450 or Q3480 Pilot Hardware. Provides all gas ignition
safety functions by controlling gas flow, ignition source,
and a 120 Vac or 240 Vac combustion air blower. The
control also monitors the appliance airflow proving switch
and limit string to assure proper appliance operation.
Provides prepurge, postpurge, timed trial for pilot igniton,
with 100 percent shutoff and continuous retry. Diagnostic
LED indicates system status.
You should have intermittent (spark) pilot light ignition. The pilot has to ignite (and be proven) before anything else will happen. The first click you hear in the gas valve is most likely the pilot part of the gas valve. Check that you have pilot light ignition. Then watch and see if it doesn't immediately turn off. If it does turn off, the flame sensor circuit is usually the problem. Cleaning the probe usually helps. Post the furnace model number.