On 4/2/2011 2:10 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.

A few years ago mine went and I happened to have a little radio shack
transformer hanging around. I wanted heat right away so I installed it
(not using the center tap). Still works. Not rated for watt I'm using
it for but I've never seen a fused or non-fused transformer start a fire
so I sleep well. I did fuse it though I forget the value.