Furnace not heating

Tempstar, Heil, Comfortmaker and Day & Night furnace not heating? Read the code for your model

Stop first: these are not a code to look up

If you smell gas

Leave the building now. Do not touch light switches or use a phone inside. From outside, call your gas supplier, or the fire department if you cannot reach them.

ICP's own words:

  • "WHAT TO DO IF YOU SMELL GAS"
  • "Do not try to light any appliance."
  • "Do not touch any electrical switch; do not use any phone in your building."
  • "Leave the building immediately."
  • "Immediately call your gas supplier from a neighbor's phone. Follow the gas supplier's instructions."
  • "If you cannot reach your gas supplier, call the fire department."

ICP, Condensing, 90+% AFUE Gas Furnace Owner's Manual, 90GSFRN-ICP-01OM, Edition 03/22, page 1

If a carbon monoxide (CO) alarm is sounding, or someone feels sick

Get everyone outside into fresh air now, then call 911 or the fire department from outside.

The U.S. Consumer Product Safety Commission's words (none of the furnace makers' documents held here prints what to do when a CO alarm sounds):

  • "Never ignore an alarming CO alarm! It is warning you of a potentially deadly hazard."
  • "If the alarm signal sounds do not try to find the source of the CO:"
  • "Immediately move outside to fresh air."
  • "Call your emergency services, fire department, or 911."
  • "After calling 911, do a head count to check that all persons are accounted for. DO NOT reenter the premises until the emergency services responders have given you permission. You could lose consciousness and die if you go in the home."
  • "If the source of the CO is determined to be a malfunctioning appliance, DO NOT operate that appliance until it has been properly serviced by trained personnel."

U.S. Consumer Product Safety Commission, Carbon Monoxide Fact Sheet, "What should you do when the CO alarm sounds?" (fetched 2026-09-24), page 1

If you see flame while the thermostat is not calling for heat

This is a stop condition. Do not reset or restart the furnace. Call a technician or your gas supplier now.

If a reset button on the furnace tripped again after it was pushed

Do not push it again. Call a technician.

ICP's own words:

  • "If it trips again, shut down the furnace and call for service."

ICP, Condensing, 90+% AFUE Gas Furnace Owner's Manual, 90GSFRN-ICP-01OM, Edition 03/22, page 10

Answer the safety questions first. Then pick the brand, say what you see on the furnace without opening it, and give the model. The code is read from the table ICP prints for that model's board, and quoted with its page. Nothing here asks you to open the furnace.

Field brief
Stop first a gas smell, a carbon monoxide alarm, flame while the thermostat is not calling for heat, or a reset button that trips again after it was pushed: each is answered at the top of this page, before any code. before any code
The code, by model read only from the table ICP prints for your model's board, quoted with its edition and page. The documents held here for Tempstar, Heil, Comfortmaker and Day & Night: 15. 15 documents
No reset step this page gives no reset or repair step, and nothing here asks you to open the furnace. A maker's reset words are shown only as the manual's words for a technician. manual's words only

What this page reads for Tempstar, Heil, Comfortmaker, Day & Night, KeepRite and Arcoaire

Each code is read from the table printed in ICP's own document for your furnace's series, and quoted with its edition and page. The documents held here:

  • F/G80VTL (Series B): ICP FG80VTL2-01SI, Edition Date 06/23 (replaces FG80VTL-01SI)
  • F/G95CSU (Series B): ICP FG95CSU2-04SI, Edition Date 7/26 (replaces FG95CSU2-03SI)
  • F/G96CTN (Series B): ICP FG96CTN2-03SI, Edition Date 7/26 (replaces FG96CTN2-02SI)
  • F/G96VTN (Series B): ICP FG96VTN2-03SI, Edition Date 7/26 (replaces FG96VTN2-02SI)
  • F/G97CMN (Series B): ICP FG97CMN2-04SI, Edition Date 7/26 (replaces FG97CMN2-03SI)
  • F/G9MXE: ICP 440 04 4311 12, 10/15/2018 (an earlier line)
  • N80MSN/N80MSL: ICP N80MSNL2-01SI, Edition Date 06/23 (replaces N80MSNL2-01SI REV A)
  • N80VSL (B series): ICP N80VSL2-01SI, Edition Date 03/23 (replaces NEW)
  • N92MSN: ICP N92MSN2-03SI
  • N95MSU: ICP N95MSU-03SI, Edition Date 7/26 (replaces N95MSU-02SI)
  • N96MSN: ICP N96MSN-03SI, Edition Date 7/26 (replaces N96MSN-02SI REV E)
  • N96VSN (amber light board): ICP 440 01 5200 00 REV D, Edition Date 06/23 (replaces REV C) (an earlier line)
  • N96VSN (Series B): ICP N96VSN2-03SI, Edition Date 7/26 (replaces N96VSN2-02SI)
  • N9MSE: ICP 440 04 4402 07, 10/15/2018 (an earlier line)
  • R96MSN: ICP R96MSN-03SI

What it cannot answer yet

For these, the page says so instead of guessing:

  • the older Series A F/G96, F/G97 and F/G95 furnaces (most units in the field): their code tables are not held, and the Series B tables are not used for them

Questions

What should I do if my Tempstar, Heil, Comfortmaker and Day & Night furnace smells like gas?

Leave the building now. Do not touch light switches or use a phone inside. From outside, call your gas supplier, or the fire department if you cannot reach them. Do not look up a code first. ICP's own "what to do if you smell gas" words are quoted at the top of this page, with the document they are printed in.

Why does this page ask for the model before it reads a code?

Because the same number of blinks can mean different things on different boards from one maker. The documents held here show it in several families, among them York, Goodman, Lennox, Allied and Nordyne: a count that is a stop condition on one board means something else on another. So a code is read only from the table printed for your model's series, and where two held documents for that series print one code with the same meaning (a misspelling or a unit written two ways) it is answered once and both are cited, while where their meanings differ it asks which unit you have and never guesses.

Can I reset the furnace myself?

This page gives no reset step. Where a maker's table prints reset words for a code, they are shown as the manual's words for a technician. Rheem's installation instructions print "DO NOT jumper or reset this switch" for its rollout switches. If a reset button on the furnace trips again, stop and call a technician. Nothing here asks anyone to open a door.