Lennox oil furnace relay control board


Old 03-13-17, 10:36 PM
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Lennox oil furnace relay control board

House built in 1955. Peerless oil furnace lasted 43 years.
New Lennox OF23Q3-105/120R-3B oil furnace installed 10/1998.
Copper trace for oil burner relay on printed circuit board (PCB) vaporized 02/2013.
Copper trace for blower motor relay on PCB vaporized in 03/2017.
Repaired both times by cleaning and repairing with a piece of Soder-Wick.
What started as an emergency repair has become more or less permanent. Not sure if replacement boards are available.
A simple repair that can be done with a soldering iron.
Repair works great!
Question: Why does the printed circuit board break down in the first place?
Is it vibration?
Lead-free solder?
Faulty PCB design?
Excessive current upon motor startup?

Here's a photo. Oil burner relay on left. Blower relay on right.

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Old 03-13-17, 11:06 PM
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Welcome to the forums.

Ahhhhh...... old radar guy. You're probably used to seeing boards with hand soldered connections that would last a lifetime.

The build quality of boards today is poor. The number one failure with these type boards is just what you've seen. There are several reasons for this.... the relay leads are not always clean, the solder wave is not hot enough, lead free solder. The RoHS Act and lead free solder is a major problem in a lot of areas. I only use lead type solder for repairs.

What these companies are supposed to do is to hand resolder any heavy pins or connections after the board comes out of the solder wave but that doesn't get done allowing sub standard relay connections to leave the factory.

I've seen this problem many times on GE oven boards.

Although I'm an advocate of repairing boards and I repair them all the time. I can't make that recommendation here, especially on a furnace board, due to safety considerations.
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