Bless your heart...did you read the first line of the original post?
Unit ignites runs for 35 seconds shuts down
Now, besides the obvious admiration you have for TJ (which I do not share), you know in your own mind that:
1. If it was the ignitor, it would not lite in the first place
2. Once the ignitor glows, the radiant sensor take the ignitor completely out of the picture and diverts the voltage to the valve coils. The unit will heat from then on until something else interrupts the circuit.
3. If anything, there is a loss of voltage, either from the radiant sensor (highly unlikely), the operating thermostat (very likely) or the blower housing is stopped up, causing the hi-limit to trip out.
Do you really think this person should invest in an ignitor now? If so, you should buy it for him.