Gas and Oil Home Heating Furnaces - Janitrol flame sensor or something else?

Gas furnace is a Janitrol GUE100-5 Rev. S, serial 8807700913, installed in this house in 1988-89 when house was built.

Burners ignite but inside 60 seconds a clicking noise begins accompanied by a buzzing noise. Within 30 seconds the burners shut off. The blower then comes on but that's just part of the cycle.

I want to swap the flame sensor out but at $170 I want to get it right the first time. I've already changed the batteries in the tstat upstairs on the small chance that may help - it did not.

$170 for a flame rod???? No way. Janitrol is notorious for having control board problems.

You are correct. It was my mistake. I searched using flame sensor, came up with a part number and found that price.

In any case, I took some steel wool to the flame sensor and cleaned it yesterday. Furnace is working as it should.

I did notice the flames, though blue, were not even from end-to-end. Most flames were tall on the ends and low in the middle. One burner had flame decreasing in height from front to back.

Sounds like the burners need to be cleaned & adjusted. Cleaning is easy but the adjustment part should be left to a pro with test equipment.

Have high efficiency natural gas furnace. during a heating cycle the burner comes on and after a while shuts off before the required temp is reached. What is happening is the upper control temperature of the plenum limit switch is reached and the burner shuts down and the process of cooling down proceeds untill the burner is once again activated.
My question is:is this situation a result of the burner being too hot for the cooling air to maintain an equiblibrum. If so can the gas valve be adjusted to provide the balance so that the burner does not cycle during the heat period? Many thanks for any input...G

You problem can be caused by several things. A weak limit shutting down the burners before it should is a possibility but not a common cause. Something common & easy to cure is a dirty fan or clogged air filter. Often, the "high efficiency" air filters create a lot of restriction & reduce air flow to the point of creating problems. Sometimes increasing the fan speed will help. Make sure all vents, both supply & return, are open & not restricted.

grady,
Thanks for your reply..I checked out what you indicated and at the same time dug out the schematics..it appears that the fan control was wired into low speed for heating and high speed for cooling. I switched the heat to medium high speed, however it still cuts off before temperature is reached..allbeit a longer wait time for it to do this..Iwill now set both heat and cool to high speed and let you know what happens...Gavin