Laars blinking green lights of death

jrkeat

I have a Laars Mascot MFTHW120 that I installed in 2020. Except for an occasional quietly recorded fan speed error, it has worked flawlessly. About 2 weeks ago, it failed completely and I got two blinking green lights—one on the front display, and one on the main board, with absolutely nothing on the screen. I had an extra control board (R2080602) around and put it in. Same thing—both LEDs briefly flashing.

But then I left it off for a couple hours and it started up!

Too weeks later, and it has failed again in the exact same way, and lengthy periods of being switched off haven't cured it. I called Laars, and the service guy there said I had a "short" and that is has destroyed both boards. I'm not sure where to go from here. I'm also not confident he is right about the boards being toast, given that the 2nd board didn't work at first and later started working. No fuses on either board have been harmed. I'm not sure what kind of short they could be taking about. The maybe the hot water circulator, the only one that runs right now, has an intermittent short?

I'm not sure where to start with trying to problem solve this. There are no obvious water leaks, burn marks, etc. I could get a new main board, but it seems like it either wouldn't work or would stop working. I could replace every bit of electronics simultaneously and hope that one of them is responsible.

Does anyone have any thoughts or experience with a similar problem?

mattmia2

is the power supply part of the board you replaced? sounds like what failed switching power supplies do

if it is a short, start with everything but power disconnected from the control board and star putting things back one at a time then start looking for shorts in the part that causes the problem to come back. the t-stat wiring or even the t-stat itself if it is electronic is a likely suspect.

Big Ed_4

You have to ohm out the loads . I always ask tech support with a meter in hand ... They would be your best bet they know where to look…. Bring a meter the next time you call :) Good Luck