Name of HVAC Parts

What is the name of the round part and the part next to it on the right.


Not sure…But let me take a stab at it before the answer is revealed…

A Plenum thermostat?

It’s got to have something to do with the high/low settings.

They look like a blower thermostat and a high limit switch.

Jim King

It is a Klixon temperature switch/control that can be normally open, normally closed or a combination of both depending on the application commonly used on furnaces as a limit switch. The oval shaped item next to the round Klixon should be the fusiable link.

It looks sorta like a ballast resister ??

limit and fusible link

Gary, try this

Would this keep the unit from coming on? I already replaced the circuit board and the transformer. That is what del air said was wrong. They wanted 300.00 for the parts. I got them for 150.00 . But I saw smoke come from the limit switch when the unit died. I told him that but he ignored me.

Yes the limit has to be in the normally closed position to make the circuit if it burns up and or opens the circuit it will not run as it is a safety control.

Why should he listen to you if he can sell you $150.00 worth of parts rather than a $10.00 limit switch. You have already exceeded the cost of a service call???

Does home depot or lowes sell these?


thanks for the help.


You tried to save yourself money and do it yourself and look what happens.

You’re better off leaving these things to the Pro’s. I know it’s tempting to Do-It-Yourself, but it always costs more money when your performing guesswork.

I have not done anything wrong. He missed the other part. I replaced the other’s. The reason I replaced the others was because it would take him 2 days to get the parts. Then they never called back.


Either way, I always take on DIY projects all the time, but (at times) I find myself bringing my unfinished work to a PRO and paying more out of pocket money than if I had brought the work to a PRO in the first place. It pisses me off at times.

I know Dave

What were you doing sitting there watching it die?! :-0

I have never seen a fuse link and a Limit switch in series like that (unless it is a roll out sensor) some where down the line. I think that is a fan controller with high limit. Is that a Carrier/Bryant/BDP? I see a lot of yellow wire in there?

Take the part out and bring it with you. You will need all the data from it. It may have to be ordered threw the equip mfg as it does not look generic.

Gary if you have a volt ohm meter you can test the klixon switch and the fused link.Just take a reading across the terminals.If you get a reading its not the controls.If you do not get a reading change the parts.Matt

If it is a fan controller, it will be normally open.

I suspect that there is something else going on.
Need someone that really knows what they are doing in there.

Hey guys I am sitting with my feet up in hotell room in Denver Made that long trip today. Class tomorrow on the B-Cam

I cut you short yesterday was trying to pack

The Klixon that was in the pic looks as if it is on the furnace am I right and what are you doing running your own furnace in A/C weather.The fan switch and limit are totally different from the fan switch or power source from the board which would operate the blower in he cooling mode.

you have me totally confused can you explain this in detail as to what mode you are concerned with.

David is correct if it is a fan control there will be no reading across the terminals,i assumed it was a limit. Assumption is the mother of all screw ups.There is probably something else going on in the system.Save time & money ,call a local pro.Matt