High-Limit-Sensors Scorched


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Old 12-29-09, 08:04 PM
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High-Limit-Sensors Scorched

We have a 10 yr old Goodman (model A36-15) HVAC system; no heat pump, no gas. While in heat mode, we have experienced an intermittent blower problem. Rapidly flipping the mode switch from OFF to HEAT multiple times has always kick started the blower. Otherwise Ė no problems. Although that problem has been irritating, we havenít attempted to fix it. But now I am wondering if our new problem is related. I mean I wonder if the heating elements have been heating up even though the blower hasnít been coming on.
Our unit was operating as usual, then without warning Ė no heat, no air flow, nothing. The breakers were all tripped. I flipped the breakers back on andÖ phzzzt! Okay, I opened up the furnace and noticed that one of the high-limit sensors that control the heating elements was scorched. I donít think the other 2 sensors are functioning either; they all appear discolored and brittle. I bypassed the one scorched sensor, and wired directly to its corresponding element in order to see if the sensor was the only break in the circuit. Only one element will activate, but whenever the blower shuts off, that one operating heating element wonít shut off. Regardless of whether the unit is turned on or off at the thermostat, that one heating element will not go off! Needless to say, all breakers are off, and the heater and I are going through a trial separation, but me and the buck stove are rekindling an old romance. HmmÖ that didnít sound right. But anyway, any ideas on helping me get my HVAC back up and running?
 
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Old 12-30-09, 05:11 AM
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Hello Mcfly!!!

You are trying to burn your house down. Do yourself a favor and get a licensed technician to look at this, at the very least you have a heat strip issue, sounds like your sequencer was bad which when left unattended lead to your heat strips overheating.
 
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Old 12-30-09, 12:36 PM
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Fan-Heat Sequencer?

Dear Dr. Emmett Brown,
This is McFly, the guy who's about to burn his house down in TN. I'm trying to get back to the future (I know... that was pretty weak). This buck stove is beginning to be a pain in my butt. The kids are tired of gathering fire wood too! Oh, and the wife has wrenched her rotator cuff in the process. But Doc, I guess you're down in LA working to keep America warm, so thanks for your time.
Anyway, you're right about me needing a tech, but I really can't afford it. I do okay with fixing stuff. Experience and exposure are what I lack here. If I replace the Fan-Heat Sequencer and all 3 high-limit sensors, do you think that might remedy my problem? All three Heat Strips look okay. If all of them don't operate afterwards, then I can replace them or just put in a new Electric Heat Kit. What do you think?
 
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Old 12-30-09, 02:57 PM
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While reading the first post and seeing McFly starting the second post, I thought I shouldn't say anything. In the third post I saw a spark of intelligence.

You have a blower problem. Probably need a new motor.

You fried your (Expensive to run) strip heat. Best to get a new one.

You are 2/3 the way to a new indoor unit.

My advise. Suck it up, find a Trane, Lennox, or Carrier dealer with financeing and put in a new heat pump system that qualifies for tax break.

There are plenty of site that offer online HVAC training, but this ain't one of them.
 
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Old 12-30-09, 10:46 PM
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Thanks for the reply J-Dad.

"You have a blower problem. Probably need a new motor."
Blower motor seems to be just fine - Never any unusual rattles, no bearing noise, no odor of an electrical short, spins easily. The blower comes on nearly all of the time. The blower rarely fails. It did have a moderate amount of dust build-up. I cleared it out with my air compressor.

"You fried your (Expensive to run) strip heat. Best to get a new one.
My advise. Suck it up, find a Trane, Lennox, or Carrier dealer with financeing and put in a new heat pump system that qualifies for tax break."

I seriously doubt that I could qualify right now. I've sucked it up all I can. I'm about to implode as it is. No doubt that a new heat pump system would be great, but replacing our unit is out of the question if our HVAC can be repaired. A new unit won't do us any good if our electricity is shut off and we're in foreclosure... you know what I mean? Otherwise, I couldn't agree more.

"There are plenty of site that offer online HVAC training, but this ain't one of them."
I'm not looking for intensive training to do this for a living. I'm just trying to determine what the likely problems might be.
Other than a faulty Fan-Heat Sequencer, can you think of any other likely reasons for the blower to not come on sometimes?
Again, thank you for your input J-Dad, and I really appreciate your time.
 
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Old 12-31-09, 04:53 PM
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Blower could have a bad capacitor causing it to go out on internal overload. It could be a bad motor, again internal overload.
Could be the tstat, evidence being your playing with the stat to get it to run.
Could be a fan bad relay.
 
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Old 12-31-09, 06:50 PM
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hard times

Times are Hard and Money is Tight I FEEL YOUR PAIN. It would absolutely be best to trade out the heat kit as a package. On a 10 yr old Goodman that kit is probably still available. Under 100 bones most likely. You can deliver some newspaper and pizzas for a few weeks to earn the needed funds. No time for sleeping when your broke. My ole grand pappy told me back years ago Quote "Son there aint but one place to go when your broke, YOU GOTTA GO TO WORK" I ain't had no sleep in nearly a year but I just got me a a brand new fancy wancy heat pump. zzzzzzzzzzzzz oh sorry did I doze off. Oh yeah and replace the blower motor capacitor that is probably the intermittent blower start problem just match the one that is on there now.
 
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Old 12-31-09, 08:54 PM
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Ahh...

Judd, J-Dad, Member,
I can't thank you guys enough. Y'all got me going in the right direction. I've already been tracking down parts, and I've got enough firewood for a couple more weeks.

McFly?! That was pretty good Dr. Brown... er, I mean Juddman. Thanks for the diagnosis.

And J-Dad, you came through for me. Thanks for sticking with me on this one. I thought you might lose patience.

"Get to Work?" Come on Member. Check my profile. I just wish I knew then what I know now. Know what I mean? Thanks for your help.

Once I get this HVAC deal settled, be looking for me in the Landscaping/Lawn Mower area. I've learned a trick or two over the years in that area. They say you've gotta give it away to keep it... Right?

Thanks again,
R.T. in Tennessee
 
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Old 01-01-10, 07:13 AM
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Pat yourself on the back too RT. If you didn't let the joking roll off we might have thought differently about who we were talking too.

I'll be looking for you when I get closer to building 16 x 4 planting beds with treated lumber this spring.
 
 

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