Kitchen Gas Appliances - Gas Dryer Starts fine but subsequent ignitions fail

My mother has a dryer with a hot surface ignitor. Sorry I failed to get the brand. There is a schematic that shows the optical sensor, glow ignitor, a two coil gas valve. If I remmember one is holding, one is assist.

Seems like a easy diagnostic, but I am not sure.

The first time you push start on the dryer it lights and climbs to temperature. then the temp limit opens and all still seems fine. Then the burner tries to ignite again. I get a glowing hot surface ignitor for oh ten seconds then a click like either a coil pulling in or dropping out. the ignitor goes cold. Then 60 seconds or so later it all starts over again.

What am I looking for here. I thought maybe temperature was a factor. but not enough to write home about.

Also I dont understand the theory as it appears that the ignitor and both coils are in parallel and it must be some sort of resistor that is between the holding and assist coils that gets bypassed by the optical sensor.

based on that do I replace both coils or which one should I concentrate on

Dan-o1

Hi:Dan-o1

Based on the problem condition you posted, I would suggest you replace both solenoids. It appears that one of them overheats and is causing the burner to shut down.

The drums internal temperature may seem warm but it may not be as warm as it should be. The determing factor could be the thermostat turning off the burner but it may be the solenoid.

A quick high limit switch test, not needed, but worth a test is to remove the exhaust vent tubing. Then turn the dryer on from a cold start. Observe the burner action thru the inspection cover.

If the same condition happens, the high limit is fine. It's then those solenoids on the gas valve. It's possible but not likely the flame sensor, thermostat nor high limit causing this condition.

You may want to remove the whole gas valve assembly, take it to the local appliance parts store and have it tested.

Check the archrives in this forum for more information, instructions, tips and safety concerns prior to attempting any repair work. Do not forget to unplug the dryer and turn off the gas valve on the supply line first!

Thanks for the help. give me a little more theory about the role of the optical sensor and what communicate the logic to it and tells it when to turn on and off. further I doubt if the solenoid is failing due to heat or do you mean internal heat and rather than ambient heat. this condition does not make sense. and since the hi limit is in series with the gas valve and ignitor. i doubt that also because the ignition cycle would not happen at all if it was open.
heeeeeellllp
dano

Hi:Dan-o1

Sorry, can't help with theory or logic of functions and operations in this type of format. Without a book, pictures and discussions in the classroom setting, a text only format such as this becomes much too long, misunderstood and takes up way too much computer server space. Questions like that get taugh in the classroom setting. <I get paid there...not here...hahaha>

You may need to remove the whole burner assembly and have it tested at the local appliance parts store. If those solenoids are defective, you could either have the service person at the counter replace them or doityourself.

Good Luck,
Tom

Hmm well ok
I appreciate your time. but is there a chance you could read my first reply and clarify if you mean internal or ambient overheating? also I dont need ohms law, power wheel theory. I wanted to know what role the optical sensor or rather the flame sensor plays? does it drop power to the assist coil after flame is prooved? again I was looking at the schematic within the inspection cover and couldn't determine which component could be suspect other than the coils. I know you said probally the coils are overheating and I wanted to know if you meant ambient or internal heat?
Please help
Dano