Furnace problem

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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.
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On Wednesday, January 21, 2015 at 8:58:09 PM UTC-6, philo wrote:

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.
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On 01/21/2015 09:08 PM, bob_villa wrote:

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
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On 1/21/2015 10:54 PM, philo wrote:

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.
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philo wrote:

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.
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On 01/22/2015 09:05 AM, Tony Hwang wrote:

Yep went through everything...
the controller does not supply voltage to the ignitor (except if furnace is left off for a few hours, then it sometimes works)
Don't want to risk repairing the control board, this being winter... as the furnace does work now if I light it manually.
Local supplier does not have the control module and it would be quite expensive. ($470 )
Since I was going to replace this 23 year old furnace this year anyway, might as well do it now.
Many folks here recommended Goodman, so I am having the local deal stop by and estimate the job in about 4 hours.
It it costs no more than two toilets I'll get it done.
(This summer a plumber told me it would be $2000 to replace a toilet that I replaced myself for $80)
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On Thursday, January 22, 2015 at 10:12:45 AM UTC-5, philo wrote:

I replaced my old Ruud with a new Rheem. Very happy with both, they are made by the same company. The Ruud went 27 years, only needed to add a hard-start kit to the AC. Rheem's been in 3 years now, 93%, two stage, variable speed blower. Really surprised at the fuel savings, probably 40%+. I was expecting a decent improvement, but that was more than I hoped for. I'm really a fan of the two stage concept too. At full output, I can raise the temp 6F an hour. That lets me get the house back up quickly after being away. It runs at low stage when maintaining the temp, ie most of the time. Without two stage if you want a bigger furnace to be able to heat quickly, then it's not going to run as much as it should to move air around, etc when it's just maintaining.
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On 01/22/2015 10:21 AM, trader_4 wrote:

The old furnace is a two-stage and I really like that...it's not a high efficiency type (80% I think) so I imagine the when I go to one, the savings on gas will be appreciated.

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On 1/22/2015 10:12 AM, philo wrote:

I've had good experiences with Goodman. Simple, reasonably well made, and they use common parts.
Unlike the proprietary Trane odd one off parts.
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philo wrote:

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 .
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On 01/21/2015 09:09 PM, Terry Coombs wrote:

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
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On Wednesday, January 21, 2015 at 9:57:43 PM UTC-6, philo wrote:

Before ordering one check the solder-side and look for cracks...it's fairly common. And look for a burned component...
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On 01/21/2015 10:27 PM, bob_villa wrote:

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.
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On Wednesday, January 21, 2015 at 10:30:38 PM UTC-6, philo wrote:

Good thought...
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On 01/21/2015 10:47 PM, bob_villa wrote:

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.
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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 .
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On Thursday, January 22, 2015 at 12:12:11 AM UTC-6, philo wrote:

Is this the board:
http://i1181.photobucket.com/albums/x430/BenDarrenBach/_14_zps714df0de.jpgBecause there are quite a few relays on it? You might be able to change-out the one for the ignitor.
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On 01/22/2015 07:15 AM, bob_villa wrote:

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.
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On Thursday, January 22, 2015 at 7:28:37 AM UTC-6, philo wrote:

I found a service bulletin that says the ignitor should be 11-18 ohms!
http://www.traneflorida.com/pdf/Service_Bulletin_4-01.pdf
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On 01/22/2015 07:47 AM, bob_villa wrote:

I looked up the specs on the exact ignitor I have and the cold resistance is approx normal
http://www.supco.com/images/pdfs/Flat%20Igniters%202.pdf
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
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