Furnace/Thermostat Issue

[pashue]

I have a Carrier Furnace, three years old. Installed a Hunter thermostat last year model 44260 - programable. Electronic pilot.

At least once a day in early morning and evening, the furnace blower will activate, the pilot comes on and then shuts off in about 5 seconds. While the blower keeps going, the pilot and or flame will come on for another 5 seconds and goes out. After about 5 tries all stops. However, the thermostat does not kick on heat as it should and then I have to activate system by either shutting off blower swith on furnace or open and close the front cover to activate blower. I have another emergency switch in hallway, which also activates blower on and off and activates system. If I don't do this, the furnace doe snot come at all. I changed batteries and filter and checked door on furnace but it is secure.Thermostat had done this earlier in season and it stopped but now it does it every day. Once I activate blower, furnace works for about 12 hours with no problem.

Please advise.

Thanks

Pashue

[HayZee518]

check out the "hot surface" ignitor. this unit almost relies on its resistance to operate. I had one in my propane stove oven that gave me problems. the wire connectors came loose so I crimped on another only to have it give way in a few days. so I used a nickel silver crimp on. this lasted about six months then problems again. I removed the ignitor only to have it catch on something and it broke into a million pieces. bought a new one for 15 bucks, installed it and haven't had another problem with it in four years!

[pashue]

HayZee518

I will look into this as it sounds as though it could be the problem. And, I did look this part p on Internet and it notes it only lasts for 3-5 years and breaks as often sometimes as a light bulb. My wife informs me our furnace is actually 6 years old not 3!
Just one question for clarification - why would the thermostat/furnace work all day long but, then have this problem around 3-4:00 A.M. If it is broke, shouldn't it not work at all? Is it because is just gets too hot and then stops working? Could it be the program mode in thermostat be corupt during the nightime phase or a resistor or part inside is faulty? It happened again this morning.

Thank you much!

Pashue

[HayZee518]

the hot surface ignitor operates on 120 volts and the thermostat is 24 volt - so there isn't a problem between the stat and the ignitor. the terminations for the ignitor needs to be tight, a loose condition will change the resistance of the unit. another new fangled safety feature. in this case the main gas valve is current sensitive and operates off the ignitor's resistance. the old formula for current is amps equals volts divided by resistance. 120 / 60 ohms = 2 amps. 120 / 40 ohms = 3 amps. 120 / 20 ohms = 6 amps. so if the main valve is seeing other then what current is meant for it - it will not open.

[pashue]

ok, I understand now.

Thanks for your help, I really appreciate it!

Pashue

[lonestarheir]

In the past I have seen a lot of problems with the hunter thermostats, and I know this sounds weird, but especially when installed with carrier furnaces. My company is a Factory Authorized Dealer for Carrier so I run. Into this problem every so often. If it were me I would try a different brand of stat and make sure that it is wired correctly by cross referencing the thermostat wiring diagram and the furnace control board diagram which can be found at www.carrier.com. You wl just need a model, series, and serial number to get it.

Hope this helps.

[pashue]

Dear lonestarheir:

Two years ago I changed the original thermostat with a Honeywell. It had problems too so, last year I bought this Hunter.

Yesterday, while I was trying to find where the surface heat ignitor is located (still can find it and will have to find manual to see where it is - inside cover data is so small I'll need a magnifying glass to read it) I noticed the front cover was loose on the bottom when removing it. It took me a while to get it on correctly. That was at 1:30 P.M. So far it is working but as stated previously, I will have to wait at least 20 hours to see if it stops working again. I did place thermostat to manual settings on Saturday but it still shut down after 20 hours.

I will probably try another thermostat if the ignitor looks ok. I believe I have thermostat wired properly or it would not have worked for almost a year - wouldn't it?.

Thanks.

Pashue

[pashue]

Well, the furnace is working fine now! I believe the problem was with the furnace cover where shut-off switch sits. I also re-set the thermostat so, I do not know 100% which was the fault.

Thank you both for all your advice. I am sure it will come in handy should I experience a similar problem.

Pashue

[pashue]

Hey guys,

Its, BACK!!!!!!!

Worked great for two whole days

So, I've checked some other sites with same problem - even with Carrier furnace and their own thermostat. Each division of Carrier blames each oher.

Now, I am going to do both - change thermostat and/or replace the surfface heat ignitor. Can someone explain where SHI is located? The only wire to area where blower and coils are, is a thing that looks like the ceramic cylinder like that of the ingitor of a gas grill that makes the spark. But there are no screws or a method of removing. Is it behind this? My area to work is limitted and I need my skinny son to actually get in there to pull cover, etc. Furnance is directly in front of water heater. Poorly built house!!!

Thanks.

Pashue

[HayZee518]

look for a round spring clip like a washer with internal "ears" it fits around the ignitor. the ignitor pushes up through a hole and the spring clip holds it in place. you'll need a screwdriver to pry up this spring clip.

[pashue]

I found this HSI and it is working fine. It gets red hot and then acually turns white a little, the flames go blazzing and then it shuts off. So, I cleaned the heat sensor probe and it now has worked fine for the past several days.

Pashue

[pashue]

I found the HSI but found it is working fine.

I cleaned the heat sensor probe, which did the trick. The heat has been working perfectly since then. I actually just rubbed it with my thumb and finger because I could not reach far enough to do a better job. Plus, I could not see how this probe comes out. It doesn not turn nor does it want yo be pulled straight out and I see no other means of removal/attachment. If it comes out from behind, I did not want to try that.

Any suggestions on how this probe is removed? The probe is the 45 degree angle version.

Thanks.

Pashue

[HayZee518]

it may just go through a hole in the bracket and has a circular spring clip - looks like a washer with teeth going towards its center. a screwdriver at different places may pry it off.