Furnace not doing as it's told


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Old 11-29-15, 03:48 PM
J
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Furnace not doing as it's told

Hello,

I have a 58gs075-ea carrier furnace from 1990. I have replaced the fan control board as well as the 3 wire pilot in the last couple of years.

I'm running into an issue where seemingly at random when the thermostat (also new) calls for heat the furnace will not kick off. I had this issue with both the new thermostat and my old one. If I turn the temp below the current house temp and then back up again it will work again for a day or so. I haven't been in the room when it fails so I'm not sure what happens when it decides not to kick off.

I found a couple videos that run through the system, but I'm not sure what I should be replacing in my situation.

common issues.
https://www.youtube.com/watch?v=JFoVcYpq1p8

video with diagram.
https://www.youtube.com/watch?v=upYhuy0AMM8

I lean toward replacing the gas valve but I don't have a good reason so I thought I would ask around.

Thanks for your time
John Warren
 
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Old 11-29-15, 03:55 PM
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Welcome to the forums.

the furnace will not kick off
You mean won't light..... it's already kicked off. Gas valves rarely go bad.

Without being there when the problem happens you will be throwing parts at it. There should be a flashing LED that will blink a trouble code when the furnace won't light. You may have to look thru a sight glass in blower door to see it.
 
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Old 11-29-15, 04:23 PM
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When the furnace is in a failed state it doesn't appear to be trying to do anything. I also don't see any lights.

I may have to setup a webcam to record and try to catch it on video while it fails.
 
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Old 11-29-15, 04:37 PM
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The model number didn't register originally. This is a 25+ year old classic here. There won't be a trouble light.

The problem will most likely be in your intermittent ignition system. Typically a pilot problem like a dirty orifice will cause intermittent problems.

Here's your manual. In there they have some good diagnostics and descriptions of how the system is supposed to operate. dms/hvac partners/docs/1009/Public/0B/58GS-3SI.pdf
 
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Old 11-30-15, 03:01 PM
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>


I agree.


Take the cover off the furnace.

Turn the thermostat up and describe the sequence of events which occurs.


When you turn up the thermostat, the gas to the pilot burner and a spark to light the pilot should turn on. The pilot should light and after thirty seconds or so, the spark should turn off and the main burner should light.

How far into that sequence does your furnace get?


Disassembling and cleaning the pilot orifice is routine maintenance that should be done once per year with this pilot switch. If kept clean, its reliable.

I always thought the manufacturer designed it to fail after 3-4 years so that a serviceman would be called to maintain the system.

Also, the furnace burners typically get rusty. If they are, you need to remove them and clean away the rust with a wire brush. This is also routine maintenance that should be done annually.
 
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Old 11-30-15, 06:35 PM
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The pilot assembly or three wire pilot is new. I just installed it two months ago. I was running into the issue before and after the pilot was replaced. I tried removing the gas line between the pilot and the gas valve and blowing it out with the air compressor this evening.

I haven't cleaned the burners. I probably need to do that.

I keep running down there when it lights up but every time I'm watching it the thing just works fine. I'll keep trying hopefully one of these times I'll catch it in the act.
 
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Old 12-01-15, 12:28 PM
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This is vague. Do you mean the furnace wont turn on or wont shut off?


>


Keep repeating the ignition sequence until it fails to light. You can turn the power switch off to cause the ignition cycle to repeat.

You need to observe the ignition sequence accurately and in detail so that you can post that sequence here.



POOR Repairman are ones who find a furnace working when they arrive and say "Well, it's working OK now. Call me again when it isn't" as they walk out the door with $100 of your money.

Intermittent problems are the bain of repairman. But most of the time they can be diagnosed and repaired the first time out IF the repairman persists in cycling the furnace until the problem repeats itself.

Your job is to be that good repairman!
 
 

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