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PovertyHillDave · Apr 5, 2009, 02:48 PM

Hi everyone,

I have a Carrier 58GS-125 electronic start furnace that has been causing my family real headaches. We have this on going problem where the furnace cycles fine, sometimes for several days and suddenly it shuts down. If we turn the thermostat down, and back up, it will start up and continue to cycle (sometimes again for days) until the system shuts down once again. All we need to do is turn the thermostat down and back up and it will fire right up again! This has been going on for several years, initially, we called a service technician who attempted to fix the problem and after several attempts and much $$$, he was never able to fix the problem. Unfortunately, looking back, I thought it was a control module (?) (but I'm not certain), that was replaced which of course didn't do a thing... the last work order receipt (from several years ago) says "replaced wiring harness", which of course didn't do a thing either. :mad: We also changed the thermostat.

Anyway... we've been living with manually turning the thermostat down and up to keep the furnace going. Then, starting a few weeks ago, I noticed the flame would go out and the blower would still be running. And this furnace turning itself off issue was happening much more often. Now, the blower would continue to run even when the thermostat was turned all the way down. If I cut the power off (via a switch mounted on the side of the unit), of course the blower would stop but sometimes only the blower would just start up and run again when the power was turned back on. I would have to turn the power on and off a few times to get the blower to say off so the furnace will ignite and cycle back on. Unless the blower was not running, the furnace won't fire up and cycle back on. And as of last weekend, the furnace blower now just continues to run. Turning the power switch on the unit off and on only turns the blower off and on... and the furnace won't ignite with the blower running.

I suspect this new issue of the constantly running blower may be a new separate problem, but I'm not sure if any of these are signs of the original intermittent issue further degrading. Are any of these symptoms common indicators of a bad component that I can attempt to fix myself? I know the furnace is an older model but really I can't afford to replace it. Right now were in a dire financial crisis due to cancer insurance/health care issues with a family member and can barely afford the basics. I'm very handy and feel confident I can carefully plug in wires to replace a bad component. Any thoughts or suggestions would be greatly appreciated. Thanks in Advance!

Dave

Joshdta · Apr 5, 2009, 03:06 PM

Sounds to me like your drian is stopped up causing the pressure switch to click out. If this is the case it would only run intill the trap filled up. Then after it would set for awhile the unit would slowly drain aloing you to turn it back on for a little bit

Joshdta · Apr 5, 2009, 03:08 PM

Sorry that info is incorrect, I did not see the electric part. Let me think here

Joshdta · Apr 5, 2009, 03:09 PM

Do you have a metal vent or plastic?

Joshdta · Apr 5, 2009, 03:10 PM

If it is plastic the drain thery would be correct

Joshdta · Apr 5, 2009, 03:12 PM

Also a bad limit switch would keep the flame off and the blower running

PovertyHillDave · Apr 5, 2009, 03:31 PM

Thanks for the help Joshdta, it has a metal vent. Would a bad limit switch put the flame out in the middle of a heat cycle, while keeping the fan running?

Joshdta · Apr 5, 2009, 03:32 PM

How is your air filter?

Joshdta · Apr 5, 2009, 03:34 PM

Yes it would, if the burner box gets to hot the flame will go out and the fan will stay on
And contiue to run till it resets its self, or in your case it is not reseting

Joshdta · Apr 5, 2009, 03:35 PM

This could also be caused by a flame role out switch on the side of the burner box

Joshdta · Apr 5, 2009, 03:37 PM

The limit switch will either be a 2 x 3 box with a metal cover on it or a 1 1/2 by 2 plastic switch. Both should be located in the top door of your furnace up high on the left or right side

PovertyHillDave · Apr 5, 2009, 05:02 PM

Thanks much... I'll try replacing that, in the upper left top panel is a approx. 3 X 4 plastic box (with circuit board inside), doesn't sound like that would be it. I'll need to take a closer looks what's on the right. I'll try whatever I can.

Joshdta · Apr 5, 2009, 05:04 PM

Most limit controls will say limit of fan timer on them

PovertyHillDave · Apr 5, 2009, 05:11 PM

I found it, it has two terminals and is on the upper right like you said. I'll see if I can pick one up on Monday. Otherwise I just found one online for $19.00. (Carrier Limit Switch P/N HH12ZB190). The picture on this web page looks just like it. By the way.. the filter is fine, just replaced it early Winter and it still looks good.

Joshdta · Apr 5, 2009, 05:18 PM

Turn the power off to the unit and peck the limit with a screw driver, sometimes that helps it reset then turn the power back on and see if the blower shuts off and the flame comes on

PovertyHillDave · Apr 5, 2009, 05:45 PM

Hmm... that didn't seem to help but I do notice a small crack running near the right terminal. Can I jump or bypass the limit switch to check it or would that not work?

Dave

Joshdta · Apr 5, 2009, 05:48 PM

Yes you can do that, just rember to turn power off till you get the jumper on.

Joshdta · Apr 5, 2009, 05:50 PM

Also, as many times as you have turned it off and on. Is there a chance you hit the fan on botton on the t-stat?

PovertyHillDave · Apr 6, 2009, 02:06 PM

Hey Joshdta,

Thanks so-o-o much! I'm thinking I owe you a steak dinner next time your in Chicago! I jumped the limit control and the furnace is once again operating.

I turned the power off, jumped the two wires that were connected to the terminals and flipped the power back on and at first the fan turned back on, but the vibration cause the jumped wires to slip and short against a pipe (slight spark) and that shut the fan off. (I know that probably wasn't the way it was supposed to go) But after that, the fan stayed off and furnace started it's spark, gas fired up and away we went.
The room temp was 49 and to test it, I set the t-stat at 52. The unit brought it up to 52 and shut down, and started right back up when the temp dropped. I then brought the room up to 65 with a few rests since the unit was running continuously without a limit control. I did notice the electronic ignitor continued to spark even after the unit fired up. Is that because of the bypassed limit control? I'll be out getting a replacement limit control this afternoon.

Joshdta · Apr 6, 2009, 03:05 PM

Glad that you have some heat. The spark ignitor also acts as a flame sencor this may be causeing it to not stop sparking, try sanding it with some sand paper or steel wool if you can get to it. It may be because of the jumped limit. I would not run with the limit jumped to long get a new one as soon as posable. Glad I could help!!