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-   -   Tempstar blower not coming on for heat (http://www.diychatroom.com/f17/tempstar-blower-not-coming-heat-159629/)

robertsm 10-10-2012 09:25 AM

Tempstar blower not coming on for heat - SOLVED
 
Make: Tempstar
Model:NUGK075DG06
Serial #: L891636239

Main symptom: My furnace blower won't come.

This started Last Friday when I fired up the furnace for the first time this Fall. Initially nothing happened and I found that the inducer blower wasn't moving (HQ1007336). I pulled that, opened it up and got it spinning. Reassembled blower housing (with high temp silicon to create good seal) and then it worked, but it was very noisy, so I replaced it with a Fasco A173. The new inducer fan works well, and now I am getting ignition of the burners. That's all good and well, but after about 68 seconds the fan/limit control (Honeywell L4064E2627) cycles through and shuts everything down, with the main blower never engaging.

On the thermostat, if I change the fan from "auto" to "on" the fan will operate. We are also having no blower issues when running A/C.

On this furnace I've got a Honeywell S8610U control board (approximately 2 years old) . When the unit's going through its cycle I'm getting the following green status/blink codes:
1 long blink/Pause/3 short blinks
--- and ---
1 long blink/Pause/4 short blinks

The blink codes seem to indicate a flame issue, but the pilot is lighting and I have solid flame coming from the burners.

Any thoughts on what to try next? Any input is greatly appreciated!

how 10-10-2012 09:54 AM

Try cleaning the flame rod.
&
watch the pilot flame through the whole cycle to see if your new ID assy is causing the pilot flame to waver away from the flame rod?

robertsm 10-10-2012 02:03 PM

1 Attachment(s)
how-
I can't find a dedicated flame sensor. Could this have an all-in-one ignitor / flame sensor? On the control board where the ignitor plugs in it says "Spark / Sense."
A picture is attached.

Thanks for the help.
Matt

beenthere 10-10-2012 03:34 PM

if the fan limit is shutting down the burner, then the flame sensor is not the problem. Could be the fan side of the fan limit is bad, or the heating speed winding of the blower motor is bad.

Try turning the fan to on at the thermostat, and then turn it to heat and set the temp up 5 degrees higher then the room temp is, and see if you get heat.

techpappy 10-10-2012 05:58 PM

just FYI that straight rod with the ceramic holder IS your flame sensor (flame rod)..It doesn't look dirty but sometimes not visible...pull it out and clean with steel wool/ metal sandpaper ..may not be the problem though

robertsm 10-10-2012 06:02 PM

Thanks to all the input so far.
I've cleaned up the flame sensor with a little emery cloth, but haven't had a chance to test it yet.

beenthere: I was thinking the same. Will check that later tonight and post back with results.

ben's plumbing 10-10-2012 08:05 PM

I thougth tempstar had control board with relays for blower control or timed cycle..seperate from limit... if blower comes on with fan on sounds like heating relay...could we see bottom of furnace with door off...ben sr

how 10-10-2012 08:51 PM

I also assumed that the tempstar's blower was motherboard controled and missed that the OP does give the numbers for a bimetal fan/limit control.
This means he is watching the control limit out without the fan coming on.

Beenthere is right, although 68 seconds is a pretty fast high limit time.

techpappy 10-10-2012 10:22 PM

So, OP...it is likely that your "fan" limit control is failing..it should turn fan on when set temp is met in heat exchanger otherwise the Heat EX gets too hot and the fan HI LIMIT shuts off the burner,,both functions are on one control..silver box that usually says FAN LIMIT right on it..if not so equipped then heat sensors are mounted on fdront of furnace heat exchanger are that convey the temperature commands via the control board so, in that casae the fan limit sensor is likely defective OR the board or fan relay as previously stated

robertsm 10-10-2012 10:57 PM

Thanks everyone. I went ahead and tried what beenthere suggested:
1) set the fan to "On"
2) turn on furnace
3) turn up thermostat to 5 F above room temp.

So, here the timeline I get doing this:
11 secs: inducer fan kicks on
13 secs: ignitor starts sparking
20 secs: pilot lights
21 secs: burners light
Everything continues on from there, with the unit not kicking off.
The fan limit control starts its rotation, and continues doing so for about 3min, but it never kicks off.

Here's a video showing the above (the thermostat was turned on about 2 seconds in): http://www.youtube.com/watch?v=9PHmNJurA_w

techpappy: Is this consistant with the Fan Limit control failing?

Thanks again everyone!

how 10-11-2012 12:46 AM

From what I could see, the video shows a fan/limit control acting normally. Whatever is preventing the blower fan from starting up was not visable to me. I would have felt more comfortable if I could have confirmed that the fan/limit control actually had three wires connected to it. (I've run into this control being used as a repair replacement part for a fan or limit only operation.) The dial temp position also looked off to these old eyes or you have one cold house.
Anyway...

The three most obvious possibilities are..

The fan/limit control is broken & is not allowing the power through to the fan lead.
The fan power lead has a broken connection between the fan/limit control and the blower motor.
The windings on the motor's heating speed are at fault.

The easiest thing to check would be to follow that fan lead from the fan/limit control all the way back to the blower motor to make sure the connections are good.
If you have an electrical meter and are comfortable using it...
The next thing would be to turn the fan back to the former auto position on the thermostat. Cycle the furnace again and measure if the fan/limit control is allowing 120V through to it's fan connection. If it isn't, then replace the fan/limit control. If it is then the motor is the likely problem.

beenthere 10-11-2012 04:33 AM

Can't say for sure, but in the video it doesn't look like the fan limit is actually wire up to control the fan.

Trace the wires back from the blower and see where they go.

At least you had heat for the night.

techpappy 10-11-2012 09:53 AM

I concur..follow the hot wire to the fan

robertsm 10-11-2012 10:03 PM

Been a long day, sorry for the slow reply back.
Here's what I find when tracing the line. See image...
http://postimage.org/image/uuv39ukc1/
Could it be the Limit Switch (522559)? Is that a NO or a NC switch?

JJboy 10-11-2012 11:17 PM

4 minutes without blower motor running...wow


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