On Apr 9, 10:24*pm, Congoleum Breckenridge wrote:
On 4/9/2011 1:37 AM, Smitty Two wrote:



In ,
* Steve *wrote:

snip

You might start at the beginning and make sure everything is hooked up
correctly. I mean, once you spring for yet another transformer. For
example, your latest fried transformer has six wires. The schematic
shows the secondary wire colors as blue and red. Given the location of
the blue and red wires on the pic of the transformer you have, that's
not quite intuitive.

And, it may not even be right. So I'd buy a new one, and check some
voltages on the bench. Put 120 into the black and white, and then
measure every other pair to make sure you understand which two wires are
really putting out 24 V.

Obviously, when you go to install it, clip and shrink tube the unused
wires, and make sure that leads are dressed so that they won't short
anywhere.

Then I'd be monitoring the damn thing, preferably with a voltmeter
perhaps on the primary and an ammeter on the secondary.

That 3rd transformer looks like a dual voltage (120/240) input.
If it is, it has two primary windings, and both need to be wire up to work.
Like this:http://www.eleinmec.com/figures/027_02.gif

To OP
this is a long shot but...
I noticed on the Trane wiring diagram that you posted that the
connections for the IGNITION circuit are shown to be near to the
connections for the primary of the transformer.

If there is some insulation problem on the ignition wires and the VERY
high voltage from the ignition circuit is sparking or jumping over to
the transformer primary circuit, this could cause the symptoms you are
seeing.

Make sure the wires that are part of the ignition circuit are not even
close to the anything else. and inspect them (with the power off) for
any sigh of cracks or other faults. These have very high voltage
like in a car spark plug and can jump several inches if there is an
insulation problem. And the problem would be intermittent. The
transformer primary voltage would look perfect except when the high
voltage spark jumps over to it and this could easily damage the
insulation on the transformer which is not designed for very high
voltages.

If you are an electrical novice, you may want to think about calling
in for some help at this point.

Mark