Help on a 1980 carrier

[tmryan1012]

I have a carrier unit that is giving me trouble. When the power is applied the inducer motor turns on and the spark for the pilot begins sparking. After the pilot lights the burners come on and seem to burn fine however they only stay on for ten seconds at best. I am stumped because I have already put in a new gas valve, three wire pilot assembly and rollout switch. I am writing asking for advice seeing as I am still fairly green in the field. I also dont want to keep throwing parts at this unit. Also customer doesn't want to replace unit at this time.

[philjafo]

Keep throwing parts at it, you will have a new furnace one price at a time.

[Strkout499]

32 year old unit? I hope you performed a safety inspection on it before you took on liability for it. You touched it, now you own it...

[tmryan1012]

I looked it over before working on it and I know that there haven't been any issues with safety in the past. This unit is in my house and due to throwing $ into it I don't have the money to put in a new unit. It's pretty sad that I can fix others units but I can't figure out my own.

[jtrammel]

Did you check the heat exchanger for cracks?

[pauls heating &]

pressure switch ok ?

[tmryan1012]

That was my next option. I know it should have been done first but it is cast and the high limit isn't tripping. Any other ideas?

[tmryan1012]

Pressure switch working properly

[2sac]

[tiger man]

I looked it over before working on it and I know that there haven't been any issues with safety in the past. This unit is in my house and due to throwing $350 into it I don't have the money to put in a new unit. It's pretty sad that I can fix others units but I can't figure out my own.

I thought you saidthat customer doesnt want to replace the furnace, are you the customer or the tech or both?

[2sac]

I thought you saidthat customer doesnt want to replace the furnace, are you the customer or the tech or both?

Or neither....

[tmryan1012]

I am both but I regularly work on commercial units

[talktowags]

Why not ask some of the guy's you work with.?? Or throw it around next time your at the supply house.?? DIY ??

[rundawg]

That was my next option. I know it should have been done first but it is cast and the high limit isn't tripping.

I'm not following how the pressure switch being "cast", and the high limit "not tripping" are related?

anyway..........

be sure you test it (the pressure switch), before you replace it. Remember, a VOM and manometer are your friends.

[Cosmicmuffin]

I had this same issue last year. system may have been running this way for years. I too replace and checked everything,and was also working with "Tech support". I finally advised customer to get an authorized Carrier Dealer tech to take a look at it. He called me back a few days later to a bid on a new furnace..,he said they could'nt figure it out either! The moral of this story.,5hours labor..,3 trips..,did not make a penny! And the "Bid" didnt get it! Good Luck!

[beenthere]

I'm not following how the pressure switch being "cast", and the high limit "not tripping" are related?

anyway..........

be sure you test it (the pressure switch), before you replace it. Remember, a VOM and manometer are your friends.

I think he means the heat exchange is cast. And since the high limit is not ripping he didn't check the HE.

[tmryan1012]

Well I think my plan of attack is to recheck the pressure switch again and recheck the high limit switch again. Im also going to pull the blower motor and control board so I can slide inside the bottom of the unit to see if I can see any part of the heat exchanger. Thanks for the help. I will let y'all know how it goes.

[rundawg]

I think he means the heat exchange is cast. And since the high limit is not ripping he didn't check the HE.

Got it. I stood up on my chair and it finally sunk in what he was saying.

Thanks.

[philjafo]

I was standing on my toilet when I finally got it.

[2sac]

I was standing on my toilet when I finally got it.

Seat up or down?