On 01/21/2015 10:47 PM, bob_villa wrote:
On Wednesday, January 21, 2015 at 10:30:38 PM UTC-6, philo wrote:
On 01/21/2015 10:27 PM, bob_villa wrote:
On Wednesday, January 21, 2015 at 9:57:43 PM UTC-6, philo wrote:
On 01/21/2015 09:09 PM, Terry Coombs wrote:
philo wrote:
I've got a Trane XV-80 furnace that just tonight quit.

When starting the ignitor /sometimes/ glows but most of the time does
not...and either way the furnace does not light.

I can light it manually with a match and it will run normally.

The ignigtor appears to be OK...no breaks and the resistance is 130
ohms
What voltage do they operate at and is it AC or DC?



Looks like it must be the controller itself and I know that is going
to be expensive.

Check that control board for dust/dirt , at the low voltage signal levels
they work at it's possible there's a short circuit - especially if there's
any condensaton/moisture present . Also possible if they used no-lead solder
that there are tin whiskers shorting something out . Also pull and replace
any signal-level control wiring plugs , sometimes a layer of oxidation can
kill the signal . Had exactly that scenario happen several years ago with a
car .




I PM my furnace every year and the control board is clean and dry.


The leads are pushed properly but I will double check,

The controller is sealed and solid state so it does not look like there
is a relay that I could replace myself.


The controller is a CNT1523 and I see them on-line for $500

Before ordering one check the solder-side and look for cracks...it's fairly common. And look for a burned component...



Ok I'll have to remove and inspect.

If it's not repairable I don't think I want to sink $500 into a 22 year
old furnace.

Good thought...




Thanks for the help...looks like I'm getting somewhere.


I took every single wire off and removed the control unit...put it on my
bench and opened it up...It's like new inside clean and shiny.

I then just put everything back together and made are all connections
were good...and I'll be darned the furnace started right up.

None of the wires or push on connectors looked burned...so it very well
may have been tarnish...

I worked with push-on connectors for my job and though it was not
common, I had seen that before.

If it stays working for the next few days hopefully it will stay that
way for a while...
but I will be seriously thinking of replacing the furnace...
but don't want to have it done in an emergency.