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dqdave1 11-24-2007 05:03 PM

carrier furnace problem
 
First time poster. I have a Carrier Cobra Natural Gas forced air furnace.
Model # is GB1AAV060155. Thermostat calls for heat, unit will start but gas valve shuts down flame before thermostat is satisfied. It will remain off till I disconnect power to unit and then it will cycle on again. I ran the test on the control board; (test to com jumper after removing R terminal and shutting thermostat to off. It tested fine. What is the problem? Also as I was running the test, I noticed that a red wire on a thermostat wire was not connectted to anything. The white from the thermostat wire was connected to comm. If I touch the red wire to the R terminal it will entergize the air condition compressor. Where does this wire connect to?

#CARRIERMAN 11-26-2007 12:20 PM

Hi dqdave1

There is only one thing that will cause this, you are tripping a limit before you finish the heat cycle. The most common cause is poor air flow or oversized furnace for application. I see yours is a 5 ton 155,000 btu, I am guessing you have a huge house with very little insualtion to warrant this kind of btu input. Check your filters first, if you are using the arm and hammer or the 3m filters with the tight pleates or a yellowish filter media. There is your problem, or if you are using an electrostatic filter otherwise known in the industry as a Paul Harvey brick and mortar filter. I would reccomend if you said yes to any of these to change the filter to a loose pleate soft media filter. Or if the system has not been sreviced properly, you could have a plugged evaporator coil and bower wheel.

Good luck
Rusty

dqdave1 11-26-2007 02:25 PM

Thanks for the reply. I have a Carrier Mechnical air filter , model 31MF 120000; It is clean, I even removed it to see if it was the problem. Code LED flashes once quickly followed by a long blink then followed by 3 short blinks before resetting it. I bypassed the high limit over load switch with no results. I now have bypassed the flame rollout switch? ( located in center of burners just above them; wire from high limit goes to it before going back to cpu.) I will know shortly if it is the cause.
I have a 4200 sq. ft house that is insulated well. Plans called for a 2 furnace system but I wanted a one furnace system with zone control for upstairs and downstairs. Big mistake. Will convert it to two furnace system when it needs changed. Unit is now 10 years old. This is first problem with system though.
Can you adise me where the red wire ( 24volt) that entergises the AC compresser contactor contects to ? it is now off after my "inspections".

dqdave1 11-26-2007 04:15 PM

update; I bypassed the flameout switch; it still locked out with a code 13 one short, long and 3 short led flashes. I now have bypassed both high limit and flame out control.
I see I have a thermopile on last burner; can this be the last option before cpu. Since I have time today to play with it; Bypassing both high limit and flame rollover did not help. Fame sensor reads .5 mamps; if I disconnect it during burn, flame will shut down, I assume it is ok. I had an extra thermostat and have swapped it out to eliminate the thermostat. Looks more like a cpu bad. The serial # is 2494A31289; What are the part #s for cpu and flame rollout switch? Prices ? Plentumn is hotter at top than at top of furnace, which I take as evaporator is not blocked.

#CARRIERMAN 11-26-2007 04:58 PM

Hi dqdave1

That helps a bunch. Look on the front of the blower door, there should be a legend that tells you what the code means. If I remember correctly that is a code for either the flue limit or for a pressure switch anomoly. Check the legend and let me know. I should be able to help you resolve this.

Good luck
Rusty

dqdave1 11-26-2007 05:09 PM

Rusty; Legend says it is a limit or flame rollout lockout; manual reset required. I bypassed both these and it still does it. Broke flame rollout switch trying to remove wire! See other posts. Forgot to mention, When I removed the flame sensor wire ( not flame rollout switch) I did get a code 34 which meant flame sensor was faulty and it would rety in three minutes; I reconnected the wire and in three minutes it relit.

#CARRIERMAN 11-27-2007 12:05 PM

Hi dqdave1

If you bypassed the limits and still have the same problem, you are going to have to replace the control board. The new board number is 325878-751 and will cost you around $250.00 for this kit. I am still betting on a bad limit at this point though. I am almost betting on the vesibule limit being bad or you have airflow issues.

Good luck
Rusty

dqdave1 11-27-2007 01:04 PM

You say vestabule limit is bad, is this the switch at the flue pipe?

#CARRIERMAN 11-27-2007 01:23 PM

Hi dqdave1

The vestibule limit is a limit that sets in the front of the furnace. It is approximately 2"x3.5" in size. On your furnace should have two red wires on it. It should be tan or a dark brown in color, it typically sets in the direct center of the furnace. It should have two screws in it that have 1/4" screw heads on it.

Good luck
Rusty

dqdave1 11-27-2007 02:37 PM

I called that a high limit switch; It has been bypassed. It had no results. Air flow seems fine at outlets; I removed air filter to be certain, no different results. I will now bypass the flue switch that moniters temp. Also there is a switch that contains a hose; it must watch air pressure; I can bypass this also. The problem is that it is intermintent and only happens occasionally. Set back thermostat takes it down to 67 degrees at night and it usually locks out during the night. Thermostat is a honeywell chronotherm IV plus.
I have been told the thermostat can cause the same symptoms as it drops it command for heat for a few seconds and then recalls it and calls for heat.
I do need to know replacement part # for the flame rollout switch as I broke it removing wire; very small; sits by center burner; wired in line from High limit ( vestuble) switch to CPU. Also I asked about not knowing where to connect wire that controlls ac contactor ( low voltage) It has to go on the y or W terminal. If I touch it to the R terminal it entergizes the compressor.

dqdave1 11-30-2007 01:44 AM

Just keeping topic at top of list. Need a few answers.

hashmat aly 12-01-2008 10:00 PM

carrier furnace problem
 
hi dqdave1 replace the FLAME SENSOR
RED WIRE:two wires goes to the condenser[OUT DOOR UNIT]if one of them is
connected to C [comon]terminal the other one get connected to the Y terminal of your Airhandler[Indoor unit].:thumbup:

HvacWiz 12-01-2008 10:27 PM

Quote:

Originally Posted by hashmat aly (Post 192505)
hi dqdave1 replace the FLAME SENSOR
RED WIRE:two wires goes to the condenser[OUT DOOR UNIT]if one of them is
connected to C [comon]terminal the other one get connected to the Y terminal of your Airhandler[Indoor unit].:thumbup:

ummm, He had this problem over a year ago, I'm sure it's fixed by now, at least I hope it is.

Ican 02-06-2010 05:07 PM

What causes the furnace and air conditioner to run at the same time? This is on the same unit, the Cobra Carrier.

Marty S. 02-06-2010 05:57 PM

Quote:

Originally Posted by Ican (Post 395776)
What causes the furnace and air conditioner to run at the same time? This is on the same unit, the Cobra Carrier.

W and Y thermostat wires shorted together. Heat pump stat used instead of a heat /cool stat would do the same.


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