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The connection between C and G looks like this here:

And SCR’s are AC devices which means they have voltage drop in either direction and in your case it 167 milli Volt

You see you got 167 if you had a short then you would get 0 - btw how is Q2? I am on an IPhone and it makes it difficult to jump between posts

Yes, these devices work with much higher voltages as your meter and at that point C and G are blocking - they go up to 200 to 1000 VAC between A and C with only a few volts needed on G to turn on

A SCR fails only in two ways: 1. It doesn’t turn ON at all 2. It turns on On all the time It basically looses its ability to act like a switch or relay

Ok, C and G are like a Diode - however it doesn’t matter - the only two questions which matter for an SCR is that A and C are conducting when G is connected to A and it stops conducting when G is removed from A - this test has to be performed in Ohm setting on DMM not diode test

Only between C and A if G is connected with an extra wire to A while A is on your DMM Plus Lead and C on the Black Lead - you need three hands for this test - G acts like an on off switch when connecting to A

Btw. did you adjust your Rheostat to 12VAC with T3 connected or did you do that before connecting to T3 - just double checking

If conducting between C and A in either direction with G not being connected to A = failed with short If not conducting between C and A when G is connected to A = failed open

Should be blocking between C and A in either direction until G is connected to A while testing

Procedure to Test the SCR with the help of Multimeter: To test the SCR, keep the Multimeter into Ohmmeter mode. Connect the positive output lead of the multimeter to the anode and the negative lead to the cathode. The multimeter should indicate no continuity. Touch the gate of the SCR to the...

What part number / device are those? I need to find the datasheet

That’s an scr with one leg being the gate and the other two anode and cathode - http://www.completepowerelectronics.com/how-to-test-scr-with-multimeter/

Ok, desolder R1 and R3 and check resistance, if they check Ok, take a close look at T1 - check primary coils for dc resistance - if they check ok check Q1 and Q2

Ok, check the six Diodes CR1 to CR6 for short - you may have to desolder each lead to test each Diode individually - if your meter has Diode test, then note voltage drop in conducting direction and check that the diode blocks in block direction

That’s good, pass now onto test 3 - you may want to connect your rheostat to 120VAC as in test 1 with phase and neutral - set to 12VAC apply that to each coil system as in wiring diagram

For test 2 I would leave only the phase 240VAC connected to rheostat and connect wiper to T2 H1 and The other phase of 240VAC connected to T2 H2 Adjust rheostat to 208VAC across T2 H1 and H2

Ok, as long it doesn’t overheat the rheostat - now the remaining tests

Take the white wire off the rheostat, connect it to one side of R2 if this neutral. Leave black wire on rheostat if this is your phase 120VAC, connect wiper to other side of R2 - apply power and adjust to 95VAC across R2 - then check voltage on VR board in DC range

Your questions make wonder if you can read / understand the wiring diagrams I posted