Thermostat question

[Cougar]

Have a Trane thermostat Model BAYSENS019B, MFG. number 91K91.
Controlling a Trane RTU.
Was working fine then one day went blank.
It's getting power, battery is good.
At first thought it was a problem with the RTU, but swapped a thermostat from another unit and it works fine.

Can anyone tell me if this thermostat is shot or is there a fix.

Thanks

 

[gmcgeo]

there are only a couple things that could be wrong,
Dead battery. " you checked that"
loose wiring or wiring problem
tripped breaker, or blown fuse
tripped safety switch
or the furnace door is opened and not closing the door switch all the way.

if you changed out the head and it it works else ware i would say wiring issue or safety switch tripped
if none of the above the thermostat is toast, i have never repaired a thermostat but i don't see why it can not be done.

 

[Cougar]

We didn’t try this thermostat on another unit.
We tried a working thermostat from another unit on this unit and it worked fine.
It appears to be a problem with the thermostat I was wondering if they are fixable

 

[Sevenhills1952]

I looked it up, they're expensive! I see used ones on Ebay, etc.
Other than basic troubleshooting, check PCB over with magnification (bad solder connection?) about all you can do.
I would call Trane customer service, maybe they have repair service or replacement recommendation.

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[Milton Shaw]

A lot of units the drain pan switch is wired to turn the thermostat off and has to be reset to turn everything back on. Thermostats do fail so keep checking it.

 

[Sevenhills1952]

The OP said it went blank, I assume meaning the display went out.

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[Cougar]

Correct, there is no display. Component next to the terminal strip looks to be the problem.
It's labeled MV1.

 

[Sevenhills1952]

Picture of it please?

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[Cougar]

Here you go.

 

[rantapawan]

Here you go.

Pins 11, 12, 13, S1 and S2 looks blown out.

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[Duke74]

Yeah. Definitely fried

 

[Sevenhills1952]

Clean those pins with alcohol and q-tip. Lightly brush with alcohol , blow dry with hair dryer on low. Check solder connections on pcb where those pins are. You may be able to salvage it. A soft bristle wire brush is good also for pins, be careful they're pretty delicate (surface mount components especially).

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[Sevenhills1952]

I tried looking closer...solder may be ok. Looks like bad pin to contact corrosion, moisture or arcing. If everything cleaned well pins and socket, use electronic contact spray, it may work.

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[Cougar]

Will clean it up, see what happens.

Thanks

 

[rantapawan]

After cleaning up, do check continuity with multimeter.

 

[Walkers]

Save yourself some frustration, put a new one on. Arc burns are bad for sensitive electronics like that. You may he able to spend several day solder in new components and save yourself $29, but it is not worth it.

 

[rburke65]

I would vote for a placement. I have no idea what would have caused that