It's SO COLD

[xjtrailrider]

what symptoms are indicative of a failed thermocouple?

The pilot and or burners will not stay lit. The thermocouple is a safety device that shuts the gas off at the controller if the pilot and or burners stop burning. It prevents explosions. They will just go bad sometimes, mostly if they are too close to the pilot/burners and get too hot. The issue I have with mine is it tends to move too far away from the pilot due to a poor bracket design and then it gets too cold and shuts off the controller. A new TC will usually fix it for a year or so.

 

[High2by]

Then scratch what I said. But the thermocouple will control the flow of gas into the appliance and if it is bad it will flow no gas.

 

[bigalpha]

I had the gas valve replaced last year because it went bad.

There is definitely gas flow; as evident by the brief periods of burning I get.

 

[xjtrailrider]

No matter what kind of pilot you have there has to be a safety device with a sensor "like" a thermocouple somewhere to let the control unit know that the burners are indeed burning (or not).

 

[bigalpha]

Well, when it stops blowing hot; the LED blinks 3 times. Research tells me that the Limit Switch is open.

Advice I received before is that teh switch is fine but there's an issue with airflow over the heat exchanger.

 

[scottmcneal]

Some of the limit switches have a little button you can push to reset..Not all, but some..HTH..Did you change your filter? How much dirt and crap is on your blower wheel? If it is real dirty it will slow air flow

 

[bigalpha]

Mine doesn't, AFAIK. When I unplug the connector that has the switch wiring, it seems to 'reset' itself.

It then ignites, stays lit for a second then goes out.

 

[scottmcneal]

Have you cleaned the thermocouple, you can use fine sandpaper or steelwool to clean ..

 

[xjtrailrider]

Well, when it stops blowing hot; the LED blinks 3 times. Research tells me that the Limit Switch is open.

Advice I received before is that teh switch is fine but there's an issue with airflow over the heat exchanger.

Does the blower turn? if so then the the fan itself may just need a good cleaning

Sorry to be asking the basics but I have learned over my 43 years of working on stuff to look at the simple stuff first and eliminate it before getting into the complicated stuff.

 

[bigalpha]

Have not cleaned the thermocouple; don't know where it's at.

Yes, the blower works fine; it blows cold through the house. The filter is clean. No obstructions as far as i can tell.

Here's my OT thread: Heating and Cooling woes

 

[kastein]

Dang. I already left a message with a place my mom used.

It was 54*F in my house this morning, except the bedroom.

oh you poor baby :spin1: We call that T-shirt weather up here.

I think it was... 9F this morning? I know it was in the low 20s Tuesday when I drove to work with no driver's window due to some vandals.

Good luck though, I hate HVAC problems.

 

[bigalpha]

9F outside is different than 54F inside.

 

[RNMedic]

do you have an air compressor?? the burners are probably dirty, they need to come out and be cleaned.

 

[bigalpha]

No I don't.

Would dirty burners cause an Open Limit Switch situation?

 

[scottmcneal]

Here is a pic of the thermocouple..It is the one with the copper line on it..

 

[bigalpha]

Never seen it and never touched it. Where is it usually located?

 

[scottmcneal]

Right by the flame, when it turns on..If it is bad the flame will turn off...Here is some pics of limit switches, one has the little button on it..

 

[bigalpha]

Can I service the thermocouple? How can I test it?

My limit switch is inside the panel for the blower -- the panel I cannot remove because of corrosion.

 

[bigalpha]

Here's a poor picture. Can get better ones.

 

[scottmcneal]

WOW..If this was mine i would break down and buy a new one..I know we offer a one and two year same as cash..Plus they have tax chit to help at the end of the year..Up to 1500 bucks..With that much RUST i would have to worry about combustion chamber being bad..Call in a company to test for leaks..Be safe..