Hi,

Dryer stopped heating again. There is 120 going to the
burner unit.

The ignitor is comming on and glowing red?

That is the place to start...ignitor workign or not working and what
happens after the ignitor gets good and hot....ignitor goes out,
ignitor stays glowing, ect.

The coils and igniter barely
light the tester. The radiant sensor and high limit light the tester
very bright. Is this a valid test?

The coils are a much higher resistance than the sensor and thermostats
are so the light will be less. But the coils on the gas valve are bad
for working once or twice and then opening up ( no continuity ) and
failing.
http://www.applianceaid.com/gas_dryer.html#noheat
jeff
Appliance Repair Aid
http://www.applianceaid.com/