Goodman Furnace Open High Limit (code: 4 blinking lights)


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Old 10-22-10, 04:32 PM
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Goodman Furnace Open High Limit (code: 4 blinking lights)

Hello,

I have a Goodman Furnace, model GDH80703AXAC, it was installed a little under a year ago. It worked fine for the first year and fine so far for this year. Until about 2 days ago. The burners went out, and when I finally got home from work and noticed it I started looking in to it. This is what I have so far:

1. Error Code: 4 blinking lights which according to the case is Open High Limit

2. Brand new furnace filter.

3. All vents going to and from the furnace are clear.

4. I tried re-seating the connections to the limit switch and powering everything off and closing the gas...then turning everything back on. Didn't work

5. I just bought a new Limit Switch and replaced it to no avail and am still having the same error.

6. I opened the blower house to check the squirrel cage fins (don't know if that's the technical term for it). It was clean, no dust. Which then I re-assembled it.

7. Posting on here

Here is what is interesting about this that I haven't really seen on any other posts. As soon as I turn the power to the furnace back on and it tries to run the blower/fan run just fine. Right away the light turns off and then starts to blink. The tube that ignites the burners (not sure of the name) never actually does anything, thus the burners never turn on. Another interesting symptom of this, is that the light stayed on twice, long enough for the tube to get hot, then before the burners ignite it shuts off and starts blinking again. That has only happened twice, and in random instances.

I really need some advice on this, because I really don't want to call in a tech.
 
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Old 10-22-10, 05:20 PM
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Normally the limit switch remains closed and only opens if the furnace overheats.

A furnace often has a diagnostic code for the limit switch opening like that.

However, a limit switch can also not stay closed properly, causing an open circuit even when the furnace is closed. Some furnaces may have a separate error code for that condition. That might be what you are observing.


You really need an AC voltmeter you can use to test when and if the limit switch is open or closed.

Diagnostic lights aren't definitive diagnostic tools. At most they merely point the repairman in a direction he should be checking on further.
 
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Old 10-22-10, 05:30 PM
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Would I be seeing that even though I replaced the limit switch?
 
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Old 10-22-10, 05:42 PM
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Probably not, but you never know. I've had new parts right out of the box fail in obscure ways that matched the previous bad part.

Still, you need to test for the condition suggested by the diagnostic code. As you have discovered, switching out parts based on diagnostic codes is not a reliable way of solving problems.

I'd also verify that the correct wires are connected to the limit switch.

If the wires and the limit switch are proven to be good and the error code still says they are bad, you have a bad circuit board. Replacing a good limit switch isn't too expensive, but if you replace the circuit board and something else is the problem that wasn't checked carefully, I predict you will be unhappy.
 
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Old 10-22-10, 05:58 PM
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Originally Posted by europe451
. The tube that ignites the burners (not sure of the name) never actually does anything, thus the burners never turn on. .
What ignites the burners? -a pilot light or hot surface ignitor glow coil? What is this tube you refer to?

Do you have a voltmeter to test the limit and safety circuit with? You can easily find out if 24 volt AC power is making it's way TO the limit switch, and then not making it's way THRU the limit switch. Once that is established, we can move in the right direction.
 
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Old 10-22-10, 06:22 PM
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ecman, it is a hot surface ignitor glow coil.

Also, no I do not have a voltmeter, so unfortunately I cannot do the test that you and Seattle suggested.
 
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Old 10-22-10, 06:33 PM
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It is a most invaluable tool - that to DIY all sorts of things - possibly saving hundreds or thousands of dollars! - I'd go get one as soon as possible. This one most well known discount tools chain store has them almost constantly on sale for $3. I buy several in case I blow one up, and/or give them away as stocking stuffers. An absolute must have.

If you had one and did that test, we could move on. I am reluctant to tell people of other "tricks" (without testing) to get the furnace running, for safety reasons.
 
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Old 10-22-10, 06:44 PM
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THe only hardware tool store around here is Home Depot, I can try looking there tomorrow.
 
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Old 10-25-10, 09:44 AM
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So it seems that model of Goodman furnace had a run of bad main boards. It turned out that it was outputting a wrong error code. There was actually nothing wrong with any of the switches, or anything for that matter. The main board was replaced and problem solved.

If anyone else has this issue then this might be what is happening.
 
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Old 10-26-10, 12:23 PM
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Originally Posted by europe451
So it seems that model of Goodman furnace had a run of bad main boards. It turned out that it was outputting a wrong error code. There was actually nothing wrong with any of the switches, or anything for that matter. The main board was replaced and problem solved.

If anyone else has this issue then this might be what is happening.
Depending on the cost of the control board though, it is most wise to rule everything else out first, with the host of tests that are quite straight forward. Nobody here wants to have to suggest to a poster that it is the control module or board, and then the poster comes back and says that did not help fix the problem.
 
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Old 10-26-10, 01:18 PM
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Guessing and supposing are not reliable diagnostic methods. Guess and suppose what the problem is, but then check to see if your theory is correct.

If you don't know how to devise and carry out those tests, hire someone who can.
 
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Old 12-13-10, 04:39 PM
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Exclamation Issues with open high limit (4 blinking lights) on a Goodman Furnace

ok so here is my situation
i have replaced the igniitor
i have replaced the circuit board
i have replaced the pressure switch
i have checked for any blockage in the ventalation system and it has a clean filter

the error light is blinking 4 times signaling the open limit switch is failing
i have had a contractor come out and it seems he is throwing parts at the situation and i am getting frustrsted
what else can i check for in order to get a better understanding of my issue?
he had said something about a cracked heat exchange..ive done some research and does this mean i need to replace my whole unit if this is the case

please help it is 18 degrees outside and my girlfriend is pissed lol
 
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Old 12-13-10, 05:40 PM
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It rapidly becomes confusing if you piggyback on older threads. I'd suggest you repost on a new thread which makes it easier to help you.
 
 

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