Help Locating Flame Sensor on Carrier 58SS Furnace


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Old 01-22-09, 12:08 PM
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Help Locating Flame Sensor on Carrier 58SS Furnace

Hello,
Can some point me to the location of the flame sensor on a Carrier 58SS induced draft gas fired furnace? Is it possibly that this unit does not have one? The only thing that is remotely similar 0is coming from the ignitor. I'm having issues with the unit starting and stopping and I would like to first try cleaning the sensor.

Thank you...
 
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Old 01-22-09, 12:33 PM
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A flame sensor is only the issue if the flame comes on for about 4 seconds then goes out, and yet the inducer motor is still going. The inducer motor remains on since there still is a call for heat by the stat. Is that your trouble?

When people have similar problem, but the flame goes out after say 30 seconds, or a minute, or whatever - often the trouble is tied into the pressure system of the furnace and can be caused by poor drafting: Condensate water backed up into the inducer and secondary exchanger because of clog in tubing or trap, loose/cracked/plugged vacuum tubing between pressure switch, gook in hole/nipple that vacuum tube connects to into the inducer housing, or a bad pressure switch itself or debris or ice in outside PVC vent pipe, (either the intake vent pipe or exhaust vent pipe.)

If you have a flame sensor rod, it be at the end of a single wire heading into the combustion chamber. The actual mount for it is usually accessible from outside the combustion chamber and is held by one screw.

Do you have a pilot light?; or is it just an HSI that directly ignites the burners? If an HSI, you may or may not have that flame sensor. Sometimes the HSI does double duty as the flame sensor. If you have pilot ignition, then you also or may or may not have a flame sensor rod next to the pilot burner inside. If you do, again you'll see the single wire leading into that area. If not, the pilot assemblies sometimes themselves become what detects the flame by a minute current that the flame creates hitting it an it follows the metal of the pilot assembly into a ground wire that goes to the control module or board.
 
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Old 01-22-09, 12:47 PM
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Well, your furnace doesn'y have the kind of flame sensor that you've probably been reading about.

Your furnace has a three wire pilot light that is lit each time the furnace turns on. The pilot light has to heat a bi-metal strip up to a suitable temperature before the main burner will turn on, but that's entirely different that systems using a hot surface ignitor.

My suggestion would be to post the problem your are experiencing, and a description of the sequence of events you see happening when the furnace lights or tries to light.

For example, when the thermostat calls for heat, the small motor (the inducer motor) above the burners should start up. Then the gas for the pilot light and a spark to light the pilot should both start, followed by the pilot light igniting. The spark should quit ticing away shortly after the pilot lights.

A couple of minutes after the pilot lights, the main burners should light, and a couple of minutes after that the fan should start circulating air around the house.

How far through that process is your furnace getting?
 
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Old 01-22-09, 06:03 PM
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Wow! I know I picked the right forum to ask the question. ecman51 and SeattlePioneer your quick responses are greatly appreciated.

My unit is an HSI. My issue first started with the pilot and burner going out within seconds. This would cycle continue for some time. Both inducer and blower were going at the same time as well. I later deduced that the blower should not continue blowing unless the unit was generating heat. Therefore, I checked my circuit board and pulled the 3 amp fuse (the one that looked like the letter E - duh!) and it was blown. I replaced it. At the same time I noticed that my filter was REALLY dirty. I left the filter out and the furnace started but with the symptom that ecman51 mention which was running for a few minutes then cutting off. However, within about 15 minutes or so after that the furnace started running and continued. I had set the thermostat to 75 but the furnace cut off at 73. Within 5 minutes or so it restarted and finally reached 75. I adjusted the thermostat to various levels to test if I would run into any more issues. So far so good. Also in the meantime, I replaced the filter.

Please let me know if you need anymore background information from me. Thanks again.
 
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Old 01-22-09, 06:19 PM
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You do not have an HSI...hot surface igniter. As S/P has said..you have a 3 wire pilot, which in addition to providing ignition it is a safety device. I think the first place I would start: Clean the pilot and then return here.
Without going into a lenthy explanantion, cleaning the pilot may allow the bi-metal strip to heat and stay heated once the burner ignites.
 
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Old 01-22-09, 06:27 PM
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So it sounds like you found the troubles, eh? You could throw someone for a loop though, by saying that the furnace would go out in seconds, because, - actually that cannot happen by say a filter causing the furnace to limit out. The furnace would have had to have ran for minutes first, INITIALLY, for that to happen. Then I'd imagine something dealing with the stress on the furnace must have taken out your fuse.

Let us know if that was your sole cause, and if things are working good for you now?

Visit some of our other forums on this board. You can save hundreds and hundreds of dollars by simply reading and learning here, in the various forums. especially if you invest in a few necessary testing tools, if you do not already have them. Tell your friends and relatives about this site, too. What brought ME to this site was it's sheer amount of subjectmatter and how active it is. Other forums of this type do not have near the amount of activity.
 
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Old 01-22-09, 06:29 PM
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As mbk3 suggested, cleaning the pilot on a furnace using the Carrier 3 wire pilot should be a matter of routine. If it's not cleaned every 2-3 years, it has a high probability of causing any of a variety of problems.

And just because you furnace made it up to the set temperature in two tries doesn't mean there's no problem. It likely has an air circulation problem that will cause the house to remain cold when you get a cold spell in your area.


Frankly, it sounds like your furnace has gone an extended period without a competent repairman inspecting it. That's usually a mistake. Fixing acute problems and neglecting chronic problems that are getting worse is not a wise idea.
 
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Old 01-22-09, 08:26 PM
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Assuming that I have to disassemble the pilot to clean it, is there a preferred method and/or instructions on how to do this for a Carrier model such as mine? Also, will I only need to use a wire brush (one of the bristles) and a can of compressed air to clean it as suggested in other threads?
 
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Old 01-22-09, 10:15 PM
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You need a 1/4" nutdriver to take the retaining screws out of the pilot burner assembly and a 3/8" wrench to loosen the conpression fitting at the end of the pilot tubing. using a hair from a wire brush to clean the pilot orifice does a good job almost all the time as long as you have natural gas.

Blowing the pilot burner and orifice out with some canned air would be a nice finishing touch, although lung power does the job fine.


Cleaning the pilot burner tends to solve a lot of problems on furnaces with this ignition system. Clean it every couple of years, a 15 minute job, and you greatly improve the relaibility of the furnace.
 
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Old 01-23-09, 12:09 PM
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SP and the rest of you - Thank you...
 
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Old 01-23-09, 06:54 PM
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Be sure to remove the orifice and blow thru the pilot assembly.
Looking thru from the tubing end with a flashlight you will notice a tube in the center. About midway there is a small hole in that tube. Make sure it is clear. And don't loose the orifice. If that hole is plugged the flame will be affected.
 
 

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