Dont guess. you may fry your AC or trip the fuses...
TRIACS for heaters (including blowers and IRONs) in general
are QUADRACs (they have a companion DIAC)
The basics to test the SCR itself (no matter 136/137/138) is
to test the GATE as a SIMPLE DIODE (0.7v drop one direction)
Then you MUST put that on the proper trigger tester (figure)
Any "timer" thing my guess is purely "external" to the mains line
as a simple switch (ON/OFF)
not much to add to the TEST CIRCUIT which BTW is defacto schematics
almost 90% of dimmers or heaters... or..
The DIAC part is tricky to test - oscilloscope will help
BTW the typical add-in DIAC is the ST DB3 or DB4 for almost any
TRIAC operating on the typical AC mains.
some EXOTIC bundles may contain the DIAC builtin as well
these are mostly advertised as QUADRACs
Paul