Furnace Won't Keep Running

[chris_s]

York - GM9S100C20DH11G

A few days ago this started acting up. Would not keep temp set on thermostat (heat). Thermostat not the problem. Furnace runs but seems to shut off after 5-10 minutes for unknown reason. Control PCB LED flashes 4 RED which means Limit SW. I replaced Limit SW but that made no difference. Same result. Also cleaned Flame Sensor Rod. Burner, igniter, blower everything else seems to be working fine, just won't keep running. Goes through about 4-6 cycles of burner starting but then shuts down. Only LED indication is 4 Red flashes. Manual says could -

"*-* RED - This indicates that a primary or auxiliary limit switch
has opened its normally closed contacts. With this fault code the control
will operate the supply air blower and inducer. This condition may be
caused - dirty filter, improperly sized duct system, incorrect blower
speed setting, incorrect firing rate or faulty blower motor. "*/-*

I cleaned the vent grills 4 months ago, but pulled them out now anyway. Same problem. Blower is running normal. Have no idea what "Incorrect Firing Rate" is.

Also, I hear a clicking "CLICK-CLICK-CLICK-CLICK" right before I get the 4 Red flashes on the status LED. Sounds like it is coming from the Gas solenoid. I am wondering if perhaps a relay went bad on the control PCB.

After it shuts down, 4 Red flash status remains. Thermostat still calling for heat. I sw the thermostat to Off, then back to Auto, and the Furnace starts back up again and cycle/problem repeats.

I'm stumped. What does it sound like to * Any *

[juster]

Do you have an electronic air cleaner. I have seen this happen that someone with an electronic air cleaner, (which he was checking) Also had a regular pleated filter that he was not checking. This caused a lack of proper air flow and error codes.

It is also a good idea as mentioned to check and clean your condenser coils (outside coil).
Any luck with your **

[ajwolck1]

Check gas pressure maybe the problem.

[nomadpeo]

the manufacturer gave you a list of possibles, most having to do with air flow issues. if you do not know how to verify proper air flow and gas flow, i recommend you call your service technician and get it thoroughly checked out. modern systems are fairly failsafe in terms of shutting down the system if a safety condition is out of range. if a limit opens, it is usually related to maintenance, for example, dirty evaporator. it could, however mean there is a blower or heat exchanger problem, in which case, it should be profesionally analyzed.