tempstar nugk075dg06

[cain]

i have a furnace that when it starts... the inducer starts then the ignition module then the pilot then the burners... before the blower turns on it cuts out on limit.. i replaced the fan/limit switch in october... could it be this again and if so what would be making it go bad so soon... i was also thinking that it could have a bad secondary heat exchanger, but i would still think the blower would run... i'm having a hard time with this one... model number NUGK075DG06... any help would be appreciated... also i wanna mention i did all of the simple test... none seem to work for me...

[catmanacman]

call your hvac contractor systems tripping on limit can be a serious problem

[cain]

i am an havc contractor... thats where the problem lies... i dont want to get too deep in it... i was hoping someone might have an idea that i didn't try.

[catmanacman]

sell them a new one problem solved

[motoguy128]

Is it a pressure limit switch, temperature limit or a flame roll-out switch that's causing it to cut-out? If it's the pressure switch, the flue could be partially blocked.

I had a [seky problem where the inducer would cut out during start-up or immediately after the burner was lit. It was intermittent and even the HVAC tech was stumped whne he came out last year. He agreed the next step was to replace the board. Replacing the control board fixed it. I'm guessing the inducer relay was a little flakey (that's a technical term).

[cain]

its a temperature limit switch, an old cam stat (which i replaced in october), there is no board on this furnace... 3 relays... a combustion relay, fan relay, and another one. i think the cam stat is bad again, which i can replace with a honeywell L4064B but i am wondering if it could be more then that... i did put in a new cam stat in october and i should have put in the honeywell limit switch... i just thoght someone might have seen this before. any thoughts?

[jwiehagen76]

Get out your meter start testing ,start logically ruling things out. What supposed to happen when. Then find out why.

[cain]

i'm going to replace the cam sat tomorrow with the L4064B but i cant figure out what would the old cam stat bad so fast. if that s even the problem. any thoughts?

[Moose]

Are you sure an L4064B is a proper replacement? I think you are missing something here. Go over the sequence of operation. If you are cycling the limit, there are other issues.

[heaterman]

Check the secondary HE