19 yr old ICP GUI100 (RPJ II), WR 50A55 Control (replaced June 2006).
I am in need of some troubleshooting direction please. When the furnace lights, it will run for approx 5 minutes with a nice even blue flame, then the flame stops. Both fans run for a short time and the furnace restarts. This will repeat for an undetermined amount of time. Some times the furnace will not light and locks out (1 flash). After shutting off power for 30 seconds the furnace will attempt to restart - the HSI will glow, the small solenoid on the gas valves clicks (I do not hear nor smell gas during this part of the cycle), the HSI goes out, and this process will repeat approx 3x's until lock-out. I have not been home during the day to observe how many lock-out cycles the furnace goes through before eventually starting again with the dreaded short cycle syndrome. Unfortunately my wife has been home during the day, and she has reported (read "not happy"
) temps in the low 60's...
So far I have cleaned the flame sensor, checked the pressure switch - 0 ohms when fan starts (with the leads jumped to check) - and 24 volts. 24 Volts to gas valve. Rollout switch closed. I did notice an interruption in the madness when I wiggled the wires to the control valve when I was checking the voltage - (it's getting late so I have not investigated this further - and the furnace is at least providing heat at this time). I have not done anything with the limit switch. As I finish this post the furnace has completed the heat cycle and is currently just waiting for another call for precious heat from the t-stat (Honeywell digital - new in 2010 and has performed great). We are looking at a forecast of 5-degrees F on Friday, so any help would be most appreciated. Thank You!!! -John