[bonifp]

Hi,

I have a Consolidated Industries Model MBA 060 NH2R, Smart Valve is HW SV9500, control unit Model ST9141A1002, part # 406650.

I was connecting a new Filtrete 3M-50 thermostat and made the mistake of connecting the blue wire from the furnace to the B terminal instead of to the "C" terminal. The thermostat smoked a bit, so I quick ran to the panel turned off the power. After connecting it correctly, I turned on the breaker and now the furnace doesn't turn on at all. No light on the control unit, zippo. I tried connecting swapping thermostats with the one downstairs and the thermostat is undamaged.

Did I fry the control unit? Looking at the furnace wiring diagram, I don't see any other fuse or breakers that could have been blown or tripped.

After reading other posts on this forum about this furnace, it appears that this unit is a lemon and this control unit failing is quite common. The furnace is ~18 years old, so it could be time for the unit to fail. I just thought it was strange that connecting this wire incorrectly on the thermostat could fry the control unit, but I suppose it's possible.

Hopefully someone can confirm that this is possible. I found one online for $129. I may try to swap the control unit from the other furnace to confirm this is bad.

Thanks in advance for any help!

 

[beenthere]

Probably burned out the transformer.

 

[danpik]

Probably burned out the transformer.

I would agree with this. You realy need a volt/OHM meter to check everything out

 

[ryandeen]

90 percent sure is your transformer, on your control board check from R to C with a volt meter
And see what you get. If 0 volt , it's your
Transformer or your line voltage coming it.

 

[bonifp]

Bingo! I swapped transformers with the other furnace and it fired right up. Now where to buy a replacement? It's a Basler BE26654003. Does Home Depot carry these? Local plumbing supply? I found one online for $19 but not sure I want to wait 3-4 days without heat.

 

[HVAC1000]

Bingo! I swapped transformers with the other furnace and it fired right up. Now where to buy a replacement? It's a Basler BE26654003. Does Home Depot carry these? Local plumbing supply? I found one online for $19 but not sure I want to wait 3-4 days without heat.

make sure it at least 40VA otherwise you will fry that one too.
http://www.homedepot.com/webapp/cat...=None&Ntpr=1&Ntpc=1&selectedCatgry=Search+All

here is one from the Home Depot that will work for you. just make sure you follow the directions for which wires to use on it

 

[bonifp]

I was able to find the exact same model/PN so I should be good to go.

Thanks everyone for the help. You saved me lots of $$ :thumbup: