New issue... Furnace won't shut off at set temperature.

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  #1  
Old 03-08-18, 04:05 PM
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New issue... Furnace won't shut off at set temperature.

Furnace Model:
G16Q5X-100-7

Hey Guys, so two months ago, you help me install a new Ignition Module, but recently I got a new problem. The furnace hasn't been turning off at the set temperature. As a temporary solution, I placed a wemo at the furnace outlet. So when it wouldn't turn off, I just set the Nest to OFF, then cut power to the wemo. When I need heat again, I turn wemo back on, and turn my Nest on. That worked for awhile, until the furnace would just continue where it left off the moment I turn on the wemo, so it no longer mattered that the Nest was still off. The furnace would just be running the moment it's plugged in.

Today, I wanted to see if all these issues I'm having the past two years was due to the Nest and the fact that I don't have a Common wire. So I installed my old Braeburn Model 3000 back. Fired up the furnace and crossed my fingers. But when it would reach the set Temp, it too didn't stop. So this is not just a Nest issue. At least it still knows to shut off the burners, but the fan just won't stop. I have to unplug the outlet manually. I'm doing the wemo trick with the Braeburn as well, so I don't have to unplug at the furnace. Once you turn the wemo off & back on, the furnace is off as it should be. But I'm wondering if this trick will eventually stop to work just like how it stopped to work with the Nest.

In any case, what do you guys think is the problem? We know that the burners still know how to shut-off. So whatever is repsonsible for telling the stat that the set temp has been reached seems to work. After that, the rest doesn't shut off. That would be the fan right? It keeps going on blowing cold air, no stopping.
 
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  #2  
Old 03-08-18, 05:23 PM
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So the problem is the blower not turning off.... correct ???
 
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Old 03-08-18, 06:57 PM
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I believe so. Burners turn off, I see the fire go out when temp has been reached, fan keeps going.
 
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Old 03-08-18, 08:58 PM
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I think I solved my issue. In learning about LIMIT FAN SWITCHES, I learned about the white knob that sets the fan to Manual or Auto. When it's pulled out, usually that means auto, when it's pushed in, usually that means manual which causes the fan to continuously run. After reading about this, I ran to my furnace to check it out. Keep in mind, my thermostat is set to off at this point. When I removed the cover, my hand brushed a few wires, and the blower turns on! Right then and there, I had a feeling I discovered my issue. So I pulled the white knob all the way out. The fan stops. I then test the thermostat setting the temp above room temp by 1 degree. I want to see if it will stop by itself, and it did.

So in the process of installing my new ignition module in January, I guess there were wires that slowly got on top of the knob, and little by little, I guess the knob started moving in. Once my module and Nest were working, there was no reason for me to keep opening the furnace, so this movement was occuring naturally I guess. Interestingly, there isn't any resistence or clicking, or detents to let you know the knob is pulled out. It's very loose. So imagine when you put the cover back and it presses against the wires and the wire presses against the knob.

Anyhow, learn something new again today. This is why we DIY, right?
 

Last edited by moctodyid; 03-08-18 at 11:27 PM. Reason: spelling
  #5  
Old 03-09-18, 12:21 PM
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Well, not everything is solved. I think I'll just say goodbye to the Nest for now. I thought everything was kosher. I thought it was just the limit fan switch being accidentally pushed in, but that wasn't it. A series of coincidental events made me think I solved the issue. When I went to fiddle with the Nest to see why it's not working properly, and tested my old Braeburn, that's when I probably accidentally pushed in the Limite Fan switch knob. So the initial issue of why the Nest went haywire is still a mystery.


The Braeburn functions as it should. Once the furnace power is turn on, it waits for the command, and it shuts off properly at set temperature. The furnace no longer responds to the Nest, and even if the Nest is turned off, the furnace will rev up the moment it gets power. It doesn't fire up the burners or turn on the fan, it's just loud and doing something. Then I would get error codes regarding the W wire, or no power to the RH wire. Basically, it has decided it's no longer compatible with my set-up or something. THere must have been some sort of update push that has rendered it useless to me. Which makes me wonder about that common wire thing.

Anyway, good thing I never threw away my old stat.
 
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Old 03-09-18, 08:48 PM
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Sometimes the inclusion of a C wire will fix those problems.
Other times it can be a defective nest base.
 
  #7  
Old 03-11-18, 04:48 PM
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PJ, can you see if we can find my common once and for all? I know a bit more about my set-up, so I can show you exactly what it is.

So at the furnace, I have this. There is a 6 wire jacket, and a 3 wire jacket.

6 wire jacket has:

Red to R
White to W
Yellow to Y
Blue to G
Brown to T
Orange to NOWHERE

3 wire jacket has:

White to Y
Red to T
Blue to NOWHERE

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But the weird thing is at the STAT, I have a 5 wire jacket:

Red to R
White to W
Yellow to Y
Blue to G
Green to NOWHERE

Is it safe to go ahead and try the green wire as the common?

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And here is the entire view of the G16Q5X-100-7 and set-up in case it may provide any clues.

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  #8  
Old 03-11-18, 05:16 PM
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Here's a thought. My old Braeburn is connected exactly the same way as the Nest, except for a red jumper cable going from RC to RH.
Since I know very little about these things, I tend to follow instructions to a T, and because NEST does not mention anything about a jumper cable going from RC to RH, so I didn't do it. Then again, Nest doesn't know about my funky 6 conductor to 5 conductor set-up.

Maybe that's why the previous installer or owners put this jumper cable? Is it safe to go ahead and do this with the Nest? Is there any reason I shouldn't put the jumper cable in from RC to RH in the Nest?

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  #9  
Old 03-11-18, 05:20 PM
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Nevermind... found this at Nest website:

If your old thermostat had a wire between two connectors like Rh and Rc (a wire that does not go into the wall), do not connect this wire to your Nest Thermostat.

Nest Thermostat connectors are built so that only one wire can be inserted per connector. Inserting more than one wire into a Nest base connector can damage your HVAC equipment and your thermostat.


Okay, it says I shouldn't do it. So we're back to post #7, trying to find my common wire.
 
  #10  
Old 03-11-18, 06:28 PM
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6 wire jacket has: ( spliced to thermostat 5 wire)
Red to R
White to W
Yellow to Y
Blue to G
Brown to T
Orange to NOWHERE

3 wire jacket has: (cable to condensor)
White to Y Y signal to condensor
Red to T Common to condensor
Blue to NOWHERE spare

T at the furnace is your common. There appears to be a splice between the 5 and 6 wire cables.You need to find that splice. Ultimately you should make green the G wire and the blue should be C.
 
  #11  
Old 03-11-18, 06:45 PM
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At the furnace, there is a BROWN wire to the Common T. Is it logical to guess that's the one that is spliced with the Green? Splice means joining two wires?
 
  #12  
Old 03-11-18, 06:52 PM
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What do you think about this G wire trick?

But the guy explains that the reason you could move G to common is because its for older systems with separate fan controls which doesn't apply to most of us, and in the video, they show an image of a fan below the furnace basically to show that most systems aren't like this anymore. But then that looks a lot like my furnace where I have the blower beneath. Base on this picture of my system, do I have a separate fan control? Should I not do the G wire trick?
 
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Old 03-11-18, 07:23 PM
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Without locating the splice it's only a guess what green is connected to.

You have a gas furnace. You can move the blue wire to C at the thermostat.
Move the blue wire from G to T at the furnace.
Add a jumper from Y to G at the furnace.
 
  #14  
Old 03-11-18, 10:03 PM
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Okay PJ, tried moving those wires around including the jumper as you described. That didn't work. It's still reving up the moment it's plugged in.

E102 error something to do with the W wire. It looks clean to me at the stat. I went to the furnace and it looked worn, so I cut it off and stripped a new end, but that still didn't work. Time to contact Nest I guess. Maybe it is a defective Nest. Because everything is fine with the old stat. And if it's defective, it probably has nothing to do with the sliver Nest display, it must be the base that it connects to that's deffective, right? Bad W1 terminal? Because man, something keeps calling, it keeps reving up the moment it's plugged in. Disconnect the Nest base and it shuts up, reconnect the Braeburn and it behaves properly.
 

Last edited by moctodyid; 03-12-18 at 12:37 AM.
  #15  
Old 03-12-18, 12:25 PM
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Just when you think you know you've isolated the issue... I have no more hair to pull out. The Braeburn today doesn't work either. It's calling for heat, but the furnace is not firing up. But at least with the Braeburn, when I turn it off, the furnace stops. But it's just not firing up now. I give up.
 
  #16  
Old 03-13-18, 04:03 PM
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Okay, I haven't given up...

I can confirm the Nest base is defective. My buddy gave me his base to test out. I'm still not getting heat, but at least with his base, the furnace doesn't rev up the moment it's plugged in. It behaves correctly, by turning on or off the furnace on command.

So both my braeburn and my friends nest base are behaving properly, but the burners are no longer starting. Remember, it was working with the braeburn while I was trying to figure out what was wrong with my nest. I think I may have shorted the spark wire somehow.

PJ, If the spark wire is damaged, I have to change the whole pilot assembly? Two months ago, I took it out to clean as you advised and it was pretty clean. The wire looks built into the pilot assembly.

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  #17  
Old 03-16-18, 11:27 AM
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Everything is working again!
 
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Old 03-16-18, 11:46 AM
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I was just re-reading this thread to reply. I see everything is working again.... now.
I guess we'll keep our fingers crossed.

I've been seeing a number of defective nest bases recently.
I don't know if that's a manufacturing issue.
 
  #19  
Old 03-16-18, 10:36 PM
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Yeah, I got a new nest base from Nest, and I used a back-up ignition module.

I must have damaged the ignition module somehow when I was trying to get the bad Nest base to work. It's only two months old, so I'm still holding out hope it's really not dead, and just needs to be unplugged or something, but I will leave well enough alone for now and stop tinkering. If the module I just installed has issues in the future, then I'll go back to testing it again, so I won't trash it.
 
  #20  
Old 03-17-18, 05:46 PM
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Gas smell....

PJ, is it normal to have a little gas smell in the furnace closet? Especially when you open the closet door, you get a whiff of it. I put my nose up against the valve, and I think it's coming from there. Labeled A in the picture below. Honestly, I've smelt this for many years. But should I worry about this? Is this something I can patch up myself? Replace the valve?

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  #21  
Old 03-17-18, 06:03 PM
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That valve should probably be replaced soon.

You mentioned furnace closet..... make sure there is enough fresh air getting into that closet for the furnace.
 
  #22  
Old 03-17-18, 06:09 PM
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The closet is in my garage. Maybe i should leave the closet door opened? Is the valve pretty much universal? I can buy any?
 
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