Weil McLain HE II control problem

cunninghamzach

Replacing a bad control on a Weil McLain boiler, with this compatible part. Power indicator light won’t turn on. Proven power at molex connector, any thoughts on what can be happening? Went through all wiring harnesses and wire connections, still nothing. 

Jamie Hall

First thought is to double check that the "compatible" connector is (or was...) actually plug replaceable. That is to say, On the plug which brings power to the unit, is the pinout actually exactly the same? Quite possible that the new unit is functionally compatble -- but that the pinout on the connectors is different. Do the check for all the plugs, not just power.

EdTheHeaterMan

I believe that part come with a new power cord that plugs into the dark 3 prong plug. Are you saying that when using the new 3 prong plug attached directly to a "Known Good" 120 VAC power supply, (like an extension cord plugged into a working electrical socket) the Power LED does not light?

If Not. then try to plug the control into a "Known Good" power source. That may tell you about the power source for the boiler.

HVACNUT

cunninghamzach said:

Replacing a bad control on a Weil McLain boiler, with this compatible part. Power indicator light won’t turn on. Proven power at molex connector, any thoughts on what can be happening? Went through all wiring harnesses and wire connections, still nothing. 

The red 3 prong molex and no power? What's "proven power"? Is that 120v across hot and neutral and across hot and ground?

What Series HE II? The control boards differ with revisions.

EdTheHeaterMan

I believe that after you plug in the 120 VAC to the board, you must also plug in the 120 VAC from the transformer to the white 3 prong plug and followed by the 24 VAC 2 prong plug from the secindary of the transformer in order to get that LED to light up.

If you have done those three things, and verified that you have 120 VAC at the dark (RED) plug, then there is a strong possibility that the 24 VAC transformer is defective.