Bad Motor or bad ST9103A1002?

jhaluska

I need help diagnosing my problem. The setup Honeywell ST9103A1002, R7184B and AF2.






The motor doesn't seem to be turning (can't prime it) and the fan circulates continuously. I have confirmed the limit has continuity and R7184B is not in lock out. I checked the transformer and have ~28V output on it.

I think a relay failed on the ST9103A1002 board, but I'm unsure how to confirm it and that the motor is working ok. What should I do next?

SuperTech

Lennox furnace? If you don't have a volt meter to check voltage to the fan motor you can remove the heating fan speed wire from the board and temporarily jump it out to L1 coming into the board to see if Thales fan comes on. Does the furnace fan run if you turn the fan switch on the thermostat to on from auto? A bad capacitor could also prevent the furnace fan from operating. 

Actually it sounds like the burner motor not operating.  I would try to reset the primary control.  If that doesn't work I would call your oil burner service provider. 

SuperTech

If the primary control doesn't need to be reset and the blower runs continuously that could be a stuck open high temperature limit switch.  Usually a plugged air filter causes that

STEVEusaPA

Simple fix. Call someone who knows what they are doing. It's easy enough for a properly trained tech to troubleshoot the equipment with a meter.

jhaluska

STEVEusaPA said:

Simple fix. Call someone who knows what they are doing. It's easy enough for a properly trained tech to troubleshoot the equipment with a meter.

It's also easy enough for me to properly troubleshoot it with my meter. The problem was intermittent so it was a little confusing. I didn't bother with further checking the pump once I realized what was going on.

The problem was a broken solder joint on the connector ST9103A with the limit. This makes the limit appear open when it's not. Another board fixed it and a simple soldering job will likely repair the old board.

SuperTech

jhaluska said:

Simple fix. Call someone who knows what they are doing. It's easy enough for a properly trained tech to troubleshoot the equipment with a meter.

It's also easy enough for me to properly troubleshoot it with my meter. The problem was intermittent so it was a little confusing. I didn't bother with further checking the pump once I realized what was going on. The problem was a broken solder joint on the connector ST9103A with the limit. This makes the limit appear open when it's not. Another board fixed it and a simple soldering job will likely repair the old board.

Great job finding the problem!