My gas furnace will not come on line when calling for heat

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carrier furnace error code 24 - ROMA Heating & Cooling ' HVAC Contractors: Furnace, Boiler and Heating Repair & Servicing

replace motor

There is a sensor in the furnace that tests to be sure the vent pipe that takes the exhaust out is clear, I had a furnace a few yrs ago where that sensor failed and it wouldn't light, it could call for heat but nothing would happen

That's a "mind of its own" condition that I've gained & lost customers over. When the unit first starts in heat, you mentioned the induced draft motor will start with no other reaction from the system, that should be the best time to locate the issue by using a volt meter. If you are getting 24 volts to MV/PV at the gas valve then you know all of the heating circuit has "proved", and that the gas valve is the problem. If not, the backtrac until you find 24v. Now if you are simply just changing parts until you find the problem, which we've all done, I believe you've changed all that you can. Check all wire connections. Its probably a loose, corroded, or damaged wire/cannon plug(the plastic plugs that multiple wires are connected), stopped up gas pilot orifice, or the gas valve its self. Hope this helps!

Your induction blower motor makes vacuum as it blows out the exhaust. these code are saying that there is no vacuum..It is probably caused by your exhaust being blocked by something. Maybe snow or ice build up due to cold temp. Try a hair dryer to heat up exhaust pvc pipe melt ice in pipe. CAREFULL do not get it so hot it melts.

is the flame igniting and then cutting off? on a gas furnace, the induction fan motor(draft motor) should start first (if the furnace is so equipped), then the flame, then the blower. if you have an induction motor (flue gas exhaust mmotor) this may be your problem (the induction motor isn't starting), if your unit doesn't have one, have you checked to see that you have gas? finally, the capacitor on the blower motor may be causing the motor not to start.

From what I saw when I googled you furnace it has a hot surface igniter. It only gets hot when it's time to light the furnace. You should be able to see it glowing red when the furnace is trying to light. The furnace has a safety feature which shuts the gas valve when it doesn't detect a flame to prevent gas build up in the furnace. There are other safety features also. If the draft inducer motor isn't running the gas valve won't open. Overheat switches some of which have to be reset manually. Adjust the thermostat until it calls for heat then observe what is or isn't happening in the furnace. It will go thru a purge cycle first. The draft inducer motor will run to do this. After the purge the hot surface igniter should get hot a glow, then the gas valve will open and the burner will light. Let me know what you find.

Armstrong

FAILURE CODES

LED Status Fault Description
Off
No Power to the System Control

Steady Flash (11 or more flashes with no pause)
Normal Operation (Standby or call for heat)

2 Flashes
Pressure Switch Closed When It Should Be Open

3 Flashes
Pressure Switch Stuck Open 30 Seconds or Longer After Call for Heat (System in 5-minute delay mode before next call for heat). On/off switch in "off" position during a call for heat will generate this code.

4 Flashes
Open Limit Switch or Limit Switch Circuit

5 Flashes
Flame Sense Signal Sensed Out of Proper Sequence

6 Flashes - pause - 1 Flash (see Note 1)*
Soft Lockout Type 1 (Failure to light within 4 trials for ignition)

6 Flashes - pause - 2 Flashes (see Notes 1 & 2)*
Soft Lockout Type 2 (Flame sense lost during run)

6 Flashes - pause - 3 Flashes (see Notes 1 & 2)*
Soft Lockout Type 3 (Pressure switch opened during run)

6 Flashes - pause - 4 Flashes (see Notes 1 & 2)*
Soft Lockout Type 4 (Limit or limit circuit opened during run)

6 Flashes - pause - 5 Flashes (see Note 1)*
Soft Lockout Type 5 (Flame has gone away after Error Code 5)

6 Flashes - pause - 7 Flashes (see Note 1)*
Soft Lockout Type 7 (Self-check failure)

10 Flashes* - SV9520H8034 only
Line Input Voltage Polarity Reversed

Check the filters first, then check for blockage in the return or supplies. An easy way to do this is by putting your hand in front of the vents to make sure accurate airflow is there. Your furnace has limit switches on it that detect heat, and if heat is getting trapped inside the unit to much, you will trip these switches and the blower will just run forever. Then you have to reset it or wait forever. But try those few things first. Hope this helps.

It sounds like you have an obstruction in the exhaust vent. Thats why when you bybass the pressure switch it runs ok. Steve