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nisad 02-18-2006 02:05 PM

Comfortmaker RPJII - 4 flashes - open high limit switch
Furnace turns on and off every few minutes. There are 4 flashes on control board meaning "open high limit switch".
Does anybody know what does it mean and how to fix?

Aceinstaller 02-18-2006 06:36 PM

Do the burners ignight and then immediately shut off right away?

Or does the unit run for a while and then the burners will shut off while the blower still runs, then reignite a few minutes later?

More than likely, a clean and check performed every heating season by a certified contractor will avoid this outcome because they will sand the flame sense rod and replace the air filter, along with many other things that prevent short cycling.

Try replacing the filter, if that doesn't solve the problem then call a certified contractor to service the unit.:o

nisad 02-18-2006 09:13 PM

I just had certified contractor at my home and he replaced ignitor. I called him because it happed that the burners ignight and immediately shut off right away. He said that would be necessary to replace limit control for second issue when the unit run for a while and then the burners will shut off while the blower still runs, then reignite a few minutes later. He didn't have a part. I am just curious what is a real issue for these 4 flashes.

Aceinstaller 02-23-2006 06:04 PM

Well, the part that he is probably having trouble with is the fan-limit control.

This limit shuts the furnace burners off when the heat exchanger gets too hot. then when the running blower motor brings the temp. back to a safe level, it tells the burner to turn back on.

there are many reasons for the heat excanger to get too hot. All of these should be checked before the fan limit is replaced. I can't tell you that your technician is wrong because I am not there to look at your furnace, but if you have any reason to dought his professionalism, call another contractor.

benmung 12-08-2006 10:14 AM

me too
I'm having the same problem with my Comfortmaker RPJ II and I have the 4 blinking lights. I'd like to try to fix it myself if possible, mainly just to get the sense of accomplishment.

What all should I look into? I've heard that a good cleanining is recommending...any tips on this?

#CARRIERMAN 12-08-2006 10:43 AM

Hi benmung

The cause of this limit switch failure is maintenace of the system. If your filter maintenance has been a little off schedule you may have more than just limit problems. The limit that is having the issue sets in the middle of the furnace and is aproxximatly 2"x4" , has two wires coming off of it. When you replace the limit you will want to get one with the exact temperature range. The one thing you will want to have done also, if the unit is equipped with A/C also, you will need to have the evaporator pulled and cleaned. They cannot just clean the stuff off the top of it, by the time you can see the stuff on the top, the coil itself is plugged. You should be able to get the limit for your furnace locally. But it is always a good idea to have a proffesional check it for the reason I above listed. Let me know if you need any further help.

Good luck

benmung 12-08-2006 10:46 AM

Is it definately a bad limit switch? The reason I ask is it seems to work sometimes and it will work for a little while if its been off for a while.

#CARRIERMAN 12-08-2006 11:33 AM

Hi benmung

This particular limit is an automatic reset limit, however it was only designed to trip about twelve times before it will become erratic. The easiest way to tell if you have a limit trip is to put a voltmeter across the terminals of the switch, when the limit shows voltage you know it has opened. The alternative method if you do not have a meter, " NOT THE RECCOMENDED METHOD", is to remove the wires from the limit and hold them together or install a jumper wire between them and see if the code goes away. If it does you will know the limit is bad.

Good luck

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