Trane (American Standard) Gas Furnace Not Working After Power Failure

Had an instantaneous power failure a few days ago, and the heat stopped working. The troubleshooting light flashes 9 times indicating hot surface igniter or ground issue. I examined the HSI and saw that both wires from the connector to the HSI were literally "fried". The insulation was burned almost completely off of the wires.

So, I replaced it with an OEM Trane IGN00145 HSI. It briefly glows (just for a second or two) and then shuts off. The draft inducer fan also turns on but only for a few seconds. I do not smell gas and the burners do not light. The furnace is an American Standard UD100C945J.

My natural gas supply is ok. My gas water heater is nearby and is working fine.

Any suggestions are most welcome and appreciated.

 

After replacing the HSI do you still get the 9 flashes ?

 

Yes. I neglected to say that.

 

Replace the circuit board/ignition control.

You have a fired board.

 

I have to agree, but beware you may have more damage than that. An electrical surge can cause things like this and can affect multiple components in the furnace.

 

Thanks for the replies. I ordered a new circuit board and will post results hopefully later this week.

 

All too true, HVAC tech!

 

Okay, I replaced the circuit board and fired it up. The system fired up, and I thought it was fixed.

Not so, it melted the insulation on my new HSI, and now I'm getting the 9 flashing lights again.

Any suggestions what is frying the wires? I don't know if the new circuit board is ruined.

These things will break your heart!

 

I got the nerve up to try the furnace again after noticing the HSI wiring insulation was burned after replacing the circuit board.

To my surprise the furnace fired up for the second time. I still don't know what to think about the burned insulation and how long the furnace will continue to operate under the circumstances.

Is it possible the heat from the furnace flames are burning the insualtion, or is it an electrical problem?

I assume the new circuit board is okay so far since the system is working (for the moment).

 

you need to watch the flames to make sure they are not burning up the insulation, but I doubt it is that unless you bought an aftermarket HSI with improper wire insulation.

 

It's not an aftermarket HSI. It's a Trane IGN00145. Since the insulation is burned off, I doubt I will be able to tell if furnace heat is melting it.

 

I would check voltage to the HSI and the amp draw with a clamp on meter.

 

I'm not sure how I would check the proper voltage on the HSI? It's an 80v silicon nitride HSI, so what voltage should the cirucit board provide to it?

I took the HSI out today to further inspect the burned wiring insulation. The insulation on both wires is only burned off about 1/3 of the way down from the ceramic portion of the HSI. The other 2/3 of the insulation (on both wires) down to the plastic connector looks ok.