Taco SR503 lights on and off

md0huazh

I have a boiler system with a Taco SR503 EXP switching relay, and it’s been running without issues for years. Today, I noticed the green light is off. When I troubleshoot by touching the board near the light or adjusting the wires, the light comes back on, and the board starts working, igniting the boiler system. However, after a heating cycle completes and the system enters another cycle, the light goes off again, and the board stops working. Does anyone have advice on what could be causing this issue? thank you.

91a23ea299045a7466daf72e563c1e49.jpeg

HVACNUT

First, I would shut off the power and tighten all screw connections AND grounds in that zone panel, and the zone panel next to it, if that's where power is coming from.

There are 2 wires under H-N. One goes to the other zones panel. Find where the other goes, and check those connections as well.

Or, it could be an internal break in the circuit board.

Joe Mattiello

check the thermostat which is your on and off switch that demands heat on and off.
simply places jumper between your thermostat terminals at top of problem zone as a validated demand to rule out thermostat issue. That’s typically the issue.
if you still have issues, contact Taco tech support at 401-942-8000 and ask for tech support.