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Furnace trouble Working on a Carrier sx from 1990, has three wire bi-metal pilot with spark and 100% lockout on the spark module. Homeowner says it only fails in cold o.d. temps (less than 35 degrees). Home owner finds unit off and silent, resets 120v and unit re-lights and runs. Don't know what parts have been replaced so far but it looks like a new spark mod. and the pilot was clean but I cleaned it again. Limit switch looks old but I think limit failure would cause the blower to run. Any ideas?

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How long unit runs after reset .If limit tripped blower motor will still run and if that's the case you might have a bad heat exchanger

Posted on May 25, 2017

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Posted on Jan 02, 2017

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SOURCE: Working on a Carrier sx

Check the heater relay on the control board found in the blower part of this furnace. It's found in a steel enclosed box
I'm having the same problem currently. I now have the blower running constantly set the thermostat to on not auto. until the part arrives
This has happened before but this time the relay has gone cloudy from sparking on and off. Tapping the relay may help just be careful when you have bypassed the door switch.
Good luck

Posted on Dec 21, 2008

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M1MB 070A BW Auto Ignite Furnace giving error code "lockout due to failed ignition." What steps do I need to take to troubleshoot?


First it will need a clean /service . Sounds like the pilot is blocked this needs cleaning as does the heater . It needs a service and a new filter . .

Oct 23, 2018 | Filter Heating & Cooling

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Heater check out list for heater failures


Almost all furnaces built after 1978 have intermittant type pilots.
Ca banned them requiring electronic spark or hot surface ignitors, followed by induced draft motors, pressure switches or centrifigal switches that "prove" a induced draft exists, allowing the pilot sequence to commence.
electronic spark type units have a high voltage low amperage spark that is AC. Fire rectifies electricity that passes through it meaning AC becomes DC ! Fire is a terrible conducter however as a result , the DC signal is only milliamps/volts signal strength. the DC prescence is proof a flame exists for pilot, and safe to commence to mainburners.

As long as pressure switches stay closed, safeties and limits stay closed
and the DC signal to the ignition module is not broken, the furnace will run.

The normal sequence of operation is upon a call for heat from the thermostat a 24 volt signal is sent to W white (heat circuit) at the low voltage terminal board on furnace.
from there depending on unit and age the heat circuit may include a circuit board, but it still has the typical limits and safetys reqired for operation
its just not using electromechanical relays to control fan and induced draft motor etc.

for the induced draft to begin ,all limits, safetys in heat circuit must be closed.

induced draft begins and a proving switch, either pressure or centrifigal close allowung the pilot to begin, a spark or hot surface ignitor is energized and a pilot flame established,modern types use flame rectification to prove a flame, older Carrier, Payne,types have a 3 wire switch in the piloyt assembly that is a bi metal that expands and contracts clicking open and shut, allowing pilot or main burners, depending if cold or hot.

pressure switches are attached with tubing to the induced draft wheel housing and sense pressure differential and close upon induced draft running, the orifices that the tube attaches to on induced draft housing often plugs or is restricted causing pressure switch to fail to close, or waver on open and close , open , close, .

if you can run the fan in the on postion , you have both high and low voltage to the furnace.

if you dont have fan control check power, breaker , fuses.

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1 Answer

How do u light the oven


GAS OVENS
The spark igniter tip is dirty (can clean it with either a little wire brush or a piece of fine sandpaper).
2) The Pilot flame is too low, and the tip of the igniter is not in the flame good enough. (the flame acts as a circuit when it touches the tip & completes the circuit).
3) The spark module is no good and needs to be replaced.(But 1 & 2 are your best bet).
spark module does not sense the flame when it's on. The spark igniter is also the flame sensor which provides feedback to the spark module.

Make sure the igniter is properly aligned with the burner lighting holes and it is clean. All lighting holes must be clean too. You can enlarge them using a drill bit one size bigger.

If it would not fix the problem, replace the bake burner and the igniter.
There is a small chance for the spark module itself to be bad as well.

The oven safety valve
(also called the gas valve) is the part that ensures that gas is not released until the igniter has reached the correct temperature needed to ignite the gas. While this part can fail, it is uncommon. If the hot surface igniter does not glow you should first verify that you have voltage to the circuit. This is a live voltage check and should be performed by a qualified person. If voltage is lost at the valve terminals then you should verify the continuity of the bi-metal in the valve using a multi-meter.


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Apr 22, 2015 | Ovens

1 Answer

I have a carrier supersavior 58ssb060-cc furnace.


i believe this furnace has a bi metal pilot safety. it may be stuck in the run position. tap the pilot switch lightly with the fat end of a screw driver and see if it resets.it is under the burners.3 wires and a tube go into it

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I posted a question about the Ultra sx 90 (Armstrong) furnace not lighting and the combustion blower keeps running. I did clean the flame sensor and no change. I also changed the spark control moduleas...


When this problem has occurred on my York furnace, the temperature limit switch had to be replaced. You may have checked this in your troubleshooting but if not, it's worth a try

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Have Goldstar Model R1804h ac/heater window unit when turned to heat blows only cold air what is easiest thing to check and purchase first.


If your thermostat is working on the Heat cycle (listen for "click" when turned up and down on Heat), then your heating coil assembly is probably bad. The heating coil is in series with a Fusible Link and a Bi-metal thermostat, if any of these three fails, there will be no heat from the coils.The Link and Bi-metal Thermostat are made up as part of the heater coil assembly.

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