U41 - burner will not light

[krc]

Regency U41. 910-028 valve per part diagram. Robert Shaw valve.
Pilot lights and holds solid flame. Yes - moved to "on".

When turn on switch main burner does NOT light.
TH - TH/TP when off is 330-335mv
TH - TH/TP when on is unchanged. I would expect a drop to fire solenoid.

Ohm-ing out switch leads...
Switch when off : TH - TH/TP OL
when on: 0 ohm

But shorting switch terminals across valve also doesn't light main burner.
that is th-th/tp
Pile voltage seems low but puzzled why i don't see a drop across the thermopile when I turn switch on.

[hearthman]

We can't give DIY advice here. See Site Rules. You are testing incorrectly. None of what you posted makes sense. If you are a tech, get your post count up so you can post in the Pro forums where we can explain and give technical advice.
Meanwhile, you need to review a technical manual on the RS valve.

Could be spiders blocking the orifice .