Lennox ml195 blowing board fuse


Old 11-20-18, 10:11 AM
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Lennox ml195 blowing board fuse

I have a 4 year old Lennox ml195 that is blowing the control board 5amp fuse when the common wite for the t-stat is connected.

When the furnace was installed it was connected to an old 2 wire turn dial t-stat which I replaced with a basic digital that was battery powered no problems there.

I wanted to upgrade again to a wifi t-stat which needs a common or C-wire so i had new 18/5 t-stat wire ran and when it was all connected the the service switch was powered on the fuse blew. It only blows when the C-wire is connected.

Heat only system
wires W/R/C are needed
Have a g/y connection on board not being used
Lennox Ml195
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Old 11-20-18, 06:42 PM
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What thermostat did you install ?
The wiring is basic..... W to W, R to Rh, C to C.
Not sure where the problem is.

ML-195-UH manual (pdf)

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