Boiler burner purge false starts

nxnorthwest

Hi. DIY homeowner new to the forum, looking for insight on some odd draft inducer behavior. I have a 20-year-old WM GV-4 Series 2 gas boiler that operates as expected most of the time: when the burner gets a call to fire, the fan purges for about 30 seconds before the burner lights. But on occasion, the fan will run for about 3 seconds, then just as the purge light illuminates on the UT 1013-10 controller, the fan will shut off. After about 30 seconds, there will be another go at the burner cycle, usually successful, but not always. At times, there can be 4 or 5 of these false starts in a row before a normal cycle runs. This behavior seems pretty random, though it did also seem to happen more frequently -- especially repeated false starts -- during a relatively cold January (lingering in single digits above and below 0). Obviously, the boiler runs more often when it's cold out, but I think the ratio of false starts to normal cycles was still a tad higher.
Thanks for any suggestions!

EBEBRATT-Ed

You probably needs to get it serviced. Sounds like an air pressure switch or centrifugal switch for the blower motor...........there is an air sw or cent sw to prove the blower is running before you get ignition. ck the wiring diagram

SuperTech

I agree that it's an air pressure switch issue. It's more likely that the tubing or the tubing ports are obstructed rather than the pressure switch is bad.

Big Ed_4

Callin an tech , let him call into tech support to find the issue ...

Big Ed_4

Pull off the vent pipe and check the inside of the draft inducer see if something is lying in the inducer housing , A miss place pipe fitting from the original instal could cause this problem ... Ask me how I know this ?

nxnorthwest

Thanks for the tips. I’ll have a look at the wiring diagram and check the air pathways. Already confirmed vent and exhaust runs outside the jacket are clear.