Nice! I just replaced the guts of the fixture and it worked. Would a 100watt lamp in a 70 watt rated HPS fixture cause the igniter to fail?
Yes. If an HPS lamp does not light, the ignitor will fail eventually because it will continue to try to light the lamp.
When troubleshooting any HID fixure with an "ignitor, or starter" (HPS, pulse start metal halide, or metal halide 150w and lower) needs to be removed from the circuit to test "open circuit voltage" , or a capacitor used with a multimeter.
Remember to only use a TRUE RMS meter when testing these.