tempstar furnace repair help

[fireman57]

I have this tempstar furnace, model number N8MPN100F-1481 manufactured in May of 2006 that the heat is not working on. The AC is fine. I replaced the circuit board in May of this year and it is still under warranty. I am getting the 3 flash code of the pressure switch being open whenit should be closed. The code is P 10. I unplugged the P1-10 plug and plugged it back in and it kicked on but only blew cool air. I unplugged it and plugged it back in again and it is back to the 3 flash code of the pressure switch. Is there an easy fix to this or do believe it is a problem in the circuit board again. Thanks.

 

[tswiczko]

Re: tempstar furnace repair help

Is it a 90+ efficient model.

There are a few things that could be causing this.

The pressure switch has a small rubber tube, make sure it is clear and connected, and make sure the port to the system where the tube hooks up is clear also(this can usually be done with a paperclip).

check the flu for obstructions ( dead birds, bee's nest, kids tennisball etc.)

If it is a 90+ eff.model, start checking drains and drain tubes to make sure they are not plugged. If it does not drain it will build up condensate and restrict airflow inside the heatexchanger that is produced by the draft inducer motor.

Let us know what you find.

 

[fireman57]

Re: tempstar furnace repair help

Is the pressure switch behind the circuit board? Btw, thanks for the reply.

 

[SS MAYFLOAT]

Re: tempstar furnace repair help

Is the draft inducer blower running? If not your pressure switch will not make (completeing the safety circuit) keeping the ignition from coming on. Make sure the blower is also running full speed. Like mentioned, check obstructions in your flue and your air intake for combustion. Either can keep the switch from making.

 

[fireman57]

Re: tempstar furnace repair help

the blower is not running. flue is clear. Ran out of time today but will shut gas off tomorrow and check condensing drain.

 

[SS MAYFLOAT]

Re: tempstar furnace repair help

Usually there is a switch on the panel covering the indoor blower (the one that delivers air to the air ducts throughout your house) This switch must be pushed in. The inducer fan is what pulls the air through the burners and out your flue. You should get line voltage going to the draft inducer motor. If not, then the board is bad. If you have line voltage (110/120 vac) then the draft inducer motor is either stuck or bad.

 

[tswiczko]

Re: tempstar furnace repair help

Is the pressure switch behind the circuit board? Btw, thanks for the reply.

Pressure switches are usually mounted in the section with the burners and inducer fan look similar to this
View attachment 120603
I believe this is for a two stage system.


"the blower is not running. flue is clear. Ran out of time today but will shut gas off tomorrow and check condensing drain."

Are you saying the circulation fan or the draft inducer is not running. if the draft inducer is not running, then locate the leads for it and put a volt meter to them and put the system in a call for heat to see if there is power going to it, there should be a molded plug that you can unplug and put your leads to.

if there is power to the inducer and it doesn't run then you probably have a bad inducer motor.

If there is no power to the inducer on a call for heat then you may have a bad inducer relay(Which is usually integrated into the cpu, but not always. not sure about your specific unit)

 

[The_Kid]

Re: tempstar furnace repair help

I have to agree with tswiczko. If the inducer motor is not running either the circuit board is not supplying voltage to the motor or the motor/motor wiring is bad, or has a bad connection. Some models of your furnace had a motor start capacitor on the induction motor so that is also a possibility. Here's a link to the service manual for your furnace. It has some troubleshooting charts that may be helpful. Hope this helps.

http://icpindexing.toddsit.com/documents/086477/44108201100.pdf

 

[fireman57]

Re: tempstar furnace repair help

Wow you guys are great. When I push the safety switch that is behind the cover I get the "heartbeat" light which they say is normal, after about 15 seconds of nothing happening it give me three flashes which says the pressure switch is open when it should be closed. Haven't had time to do anything this am as busy with work. tsw the attachment would not open. Kid thanks for the manual that is awesome. haven't tried to open it yet.SS i assume you are talking about what I am calling the safety switch. Nothing happens except the green light that I have described.

 

[tswiczko]

Re: tempstar furnace repair help


Sorry About that, I believe the first two are two stage switches and the third is a sinlge stage

 

[fireman57]

Re: tempstar furnace repair help

I got it running but I really don't know how. I turned off the gas to house and unscrewed the condensation drain which was dry. Decided to try it and it worked. Now I just have a loud whine. I'll find it tomorrow. If not I have the manual to trouble shoot from. You guys are fantastic and many heartfelt thanks, especially from my bride Julie.

 

[tswiczko]

Re: tempstar furnace repair help

I got it running but I really don't know how. I turned off the gas to house and unscrewed the condensation drain which was dry. Decided to try it and it worked. Now I just have a loud whine. .

Did you pull the flue apart at the inducer or just look down it from the end.

I ask this because I have found many birds and squirrels right at the inducer motor in the flue sometimes they would prevent the motor from turning other times they would stop the flue draft when the motor was running and yet sometimes the system would run but make an awful sound because the beak or a foot was rubbing on the inducer fan.
http://www.youtube.com/watch?v=6T21kwpzjbU

 

[fireman57]

Re: tempstar furnace repair help

My flue is capped so nothing can get down in there, even wasps because of the mesh on the cap so I doubt that it is animal in there. I'll try to determine where the whine is from today. Thanks again guys for the help this is a helluva site just to read about things on. I do auto, home, and outboard repair but when I get stuck you guys always come through.

 

[SS MAYFLOAT]

Re: tempstar furnace repair help

On my commercial units, many times with them not being in heat mode all summer the inducer motor will stick. Usually just bumping it will get it going, and of course sometimes the are froze up solid requiring a new motor.

Putting screen over the flue makes for good insurance to prevent critter intrusion.