On Apr 2, 12:10*pm, Steve Turner
wrote:
A couple of months ago the heater quit coming on in my upstairs Trane XB80 HVAC
unit. *It's been off warranty for about 2 years, and I am enough of a
do-it-yourselfer that I'm comfortable with simple repairs. *I found that the
LED on the control board was not lighting up, and subsequently found that I was
not getting 24V output from the 115V-24V transformer. *Sure enough, the 24V
circuit was open, so I found a local replacement transformer (not the exact
form factor, but same specs) and things worked fine after I replaced it. *Now,
I have the very same problem (only this time it's the A/C that's trying to come
on; not that it matters), and once again 24V is missing on the output side of
the transformer. *This time the 24V circuit has continuity, but the 115V
circuit is open. *Of course, I can replace the transformer AGAIN, but I'd sure
like to know what could be causing this problem... *Any ideas would be
appreciated. *Thanks.

Per other post...

And of
course lighting can cause surges to destroy things like this too.

the problem may be on the supply side rather than the load side.

I would suggest a surge protector of some sort on the supply side.

and as others have suggested, a better / continuos duty higher rating
transformer from Newark.

cheers
Bob