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.
How old is the ignitor? The resistance sounds right and its AC. You may have a solder break on the controller relay, giving you the intermittent.
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 .
The ignitor is maybe 8 years old and I took it out and it looks good...
When I turn the furnace on, at the time the ignitor should be glowing I'm only getting 4 vac at the leads which I know is too low to make it glow.
My guess however that it needs more than 24 volts as I applied 24 volts to it and it only got very slightly warm
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.
Must have just been a fluke
the furnace ignitor did not work a 2nd time
Since I can light it manually and the temp here is moderate...even though it looks like new furnace time...I at least won't have to make it an emergency call
plus...we have a 220v baseboard heater that can keep the upstairs quite warm even without a furnace .
What little I know of furnace igniters, typically
110 VAC.Some units, they detect the amperage of the igniter, won't open the gas valve if it's too high or low. You mention match light, so that's not an issue.
The so called "Molex" connectors, nylon plug with several pin and hole connectors, known to go bad. It's a wise idea to spray em with WD=40 when you put them back together. That displaces water, and helps the connection.
- . Christopher A. Young learn more about Jesus .
Is this the board:
That photo was very small and it was hard to make out...but the board does have a lot of relays on it and...yes I could figure out which one is for the ignitor and change it...
Were it summer now, I'd do it
However since the furnace is semi working now...I'm not sure I want to take the chance of taking it out completely
Plus I found out that if I turn off the input power for a few hours, then turn it back on, it will start normally without me having to light it.
I found a service bulletin that says the ignitor should be 11-18 ohms!
Sorry, the image was larger on ebay and could be magnified.
I looked up the specs on the exact ignitor I have and the cold resistance is approx normal
Plus it /does? work when there is 115v on it.
The problem is that the output is only usually 4 volts... but if I turn the furnace off for a few hours and turn it back on...the first time it does supply the right voltage.
Anyway this was the year I was going to replace the furnace anyway and I now have a contractor coming out to give me an estimate on a new one.
Also: I got a look at the 2nd image you posted and it's not the same control that I have...but it's somewhat similar.
There is a Trane parts depot here in town and they do not have a control in stock, they'd have to order it
Thank you very much for the great help
Hi, Most trouble part of a furnace is HSI and flame sensor. HSI needs replacing, flame sensor needs cleaning. HSI is like ~40.00 or so. I'd just put in a new one and see. I always keep spare HSI, one at home abd one at cabin. HSI is like big filament in a light bulb. With age it won't produce high temp. It has to glow real bright red when it is on. Worth checking loose connector too. You can tighten the connector female pins.
Hi, If you suspect relay, there is one for HSI It is very small. I replaced a relay once on my old furnace with one for laser printer fuser control circuit. Small molded piece with 4 pins sticking out, rated at like 3 Amp./120V AC rated contacts.
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