Estate Model # TGDS740JQ1

[Waneewek]

I have a LP gas dryer that won't heat, no gas.  I have gas to the dryers shut off valve and it's open.  The igniter glows with the call for heat, and  I have 120 volts to the coils.  I checked the orifice and it is not plugged.  I replaced the coils and that didn't solve my problem.  Have you ever heard of the gas valve going bad on a dryer or am I missing something? 

 

Wan

[Pegi]

Not very often but it does happen, if the igniter cycles on and off and the coils are new and there is gas to the gas valve something seems to be wrong with the valve?

[RegUS_PatOff]

Has this dryer been is storage till now ?

The Gas Valve could rust if the plastic cap wasn't replaced over the Gas Line Stub.

 

Does the Igniter ever stop glowing (after it reaches temperature) ?

The Flame Sensor Switch could be stuck closed

[Waneewek]

The dryer was not in storage.  They were using it and it quit heating.  If the flame sensor was stuck closed would I get voltage to the solenoids? 

Wan

[RegUS_PatOff]

You'd habe boltage accross the

Igniter

Hold Coil 1 to 2

Assist Coil 1 to 3

but not the Main Coil 4 to 5

[Waneewek]

regUS: I must be missing something here.  Can you explain the burner operation to me?  I sure would appreciate that.

Wan

[RegUS_PatOff]

[Waneewek]

What's the purpose of the booster and holding coils?  It looks like the booster and the holding coils are always energized.  Where is the holding coil?  From looking at the diagram, I don't see what prevents the secondary coil from energizing.  How does the result of the flame sensor opening energise the secondary coil?  Is it because the current will follow the path of least resistance that makes this work?

Wan

[RegUS_PatOff]

I haven't studied it much, but it's a complex safety circuit,

used by almost all the major appliance makers for more than 30 years (I'm not sure how long)

There's (3) coils (windings)

They used to be (3) separate "shafts".

Now the Booster and Secondary coil windings are on the same "shaft".

The Holding Coil is separate.

None of the Coils by themselves, can open the Gas Valve.

They must be energized in the correct order.

The Holding Coil is always energized (until the Dryer Thermostat opens)

The Booster Coil and Igniter (in parallel) are enegized until the Flame Sensor Switch

detects the correct amount of heat from the Igniter, then the Flame Sensor Switch opens and it is now in series with the (Booster Coil & Igniter).

Now add to that equation that because of all the thermal cycling of the Coil Windings, they often go bad,

open internally, intermittently (when warm), and are hard to measure which Coil is "open".

For $20 for the set of (2) Coils, it's not worth the bother to try to determine which one is bad. 

[Waneewek]

Thanks regUS!