No heat - SmartValve SV9501/SV9502 pilot does not light or main burner does not come on

What is going on

Step-by-step check of the intermittent-pilot SmartValve ignition on RGAC/SGAC units.

Likely causes

• No 24 V at the control harness (power, transformer, limit, thermostat, wiring, combustion air proving switch)
• Igniter / flame rod assembly failed
• No pilot gas (air in the pilot tube)
• Low 24 V supply while the igniter is on
• Weak pilot flame contact on the flame rod
• Failed SmartValve control

Check in this order

1. Check the pilot burner element it should measure less than 10 ohm at room temperature.
2. Turn gas off, SmartValve switch ON, unplug the control harness and call for heat. You need 24 V between 24V common and the thermostat / pressure switch pin, and between 24V common and 24V hot. If not, check line power, transformer, limit, thermostat, wiring and the combustion air proving switch.
3. Plug the harness back in and wait for the self-check / pre-purge. The igniter should glow red. If not, measure about 24 V at the HSI output with the pilot cable connected: 24 V present = replace the igniter/flame rod; no voltage = replace the SmartValve.
4. Turn gas on - the pilot should light. If not, make sure pilot gas flows and the tube is purged (recycle the call); measure at least 19.5 VAC between 24V hot and common with the igniter powered (check transformer and line voltage if lower); if voltage is OK replace the igniter/flame rod.
5. If the pilot lights but the main valve does not open: check the pilot flame touches the flame rod well and the pilot tubing connection is good; if both are good replace the igniter/flame rod, then cycle the thermostat. If the main burner still does not light, replace the SmartValve.
6. Note the igniter cycles off and on once during the 90-second trial; take all voltage readings while the igniter is powered and be careful not to damage the terminals.