LG DRYER WON'T STAY LIT

[kandbs]

My problems started with a fairly common issue, dryer (DLG7188MW) starts, igniter energized, flame lights, runs until thermal shutoff, then flame will never start again.  even though sequence appears normal, can hear thermostat reset, igniter, then nothing.  all components checked out, after troubleshooting for a couple days it's gotten to the point where it won't light at all.  voltage readings show valve 2 is not getting any voltage after the igniter de-energizes, valve 1 is getting 100 VDC when igniter starts.  the wiring schematic does not tell me what needs to be satisfied to get voltage to valve 2, but I suspect its only the control board (and the flame detect opening, which happens as igniter is de-energizing).  Can anybody verify that?  Also, according to my service manual, the gas valve has valve two connected to the gas inlet, while one is at the bottom, but my wiring clearly has valve two leads going to the bottom valve, as is, harness for valve 2 won't even reach the top valve.. been like this since bought, 3 years.. am assuming it does not really matter since they are in series and the goal is to get them both open..

I suspect the control panel, but hard to verify, any thoughts?

[JWWebster]

The valve resistance is 1995 ohms and the ignitor is 185. 

[kandbs]

let the dryer sit overnight and went through start sequence.. first time, started up no problem.. reached temp, gas shut off, cooled off, igniter started, no gas. no voltage to valve 2. 

The question then is, if any of the thermo cutoffs are open, will the igniter still get power, or does the fact that the igniter starts indicate that all temp relays are closed?  the answer will determine if I by a control board or one of the sensors..

[JWWebster]

It ain't gonna be a limit it is gonna be the coil. Getting hot and failing.

[kandbs]

I keep waffling on the valve/coil because I get voltage to valve 1, but I get no voltage to valve 2, I don't read voltage coming off the main board to the number 2 solenoid when the igniter shuts off, at the board or at the solenoid.  Should see potential at the leads to the solenoid if they are removed during the cycle.

[JWWebster]

do you have a repair manual?

[kandbs]

I have the Service manual and have gone through all the troubleshooting steps.  All components check out with values in manual.  The electrical schematic leaves a bit to be desired as the wiring shows going to the control board, but not the interconnections on the board, particularly terminals BL2 - YL2 and BL3.  During troubleshooting I disassembled dryer to bare shell, tested all components and inspected all wiring.. Went out this morning and again fired up.. it ran through it's gas restart cycle 3 times before failing, I felt the solenoids and they were both cool to the touch.  I jumpered the hi-temp thermo to no affect.  Can't reach the thermostat on air duct when have assembled for testing, but assuming since it is going through it's restart (igniter energized) the thermostat is calling for heat okay.  It does seem to be a temperature related issue.  I would really like to eliminate all the sensors as the problem, and if I knew that they all have to be closed for the igniter to fire then I could do that, but cannot tell from wiring diagram if that is the case.   If today is like yesterday, it won't restart for the rest of the day.  (it's 100 degrees in the garage where I'm testing during the day could be something is cooling down overnight enough to function.. ).. thinking on that, I'm going to try to cool down the solenoids using my compressor. just for something else to try.

[kandbs]

well cooling down the coils with a airstream between cycles apparently wasn't a good idea, the dryer is tripping the power breaker now.. time to disassemble again..

[kandbs]

. I pulled the igniter and noted it was CRACKED.. but it still passed current and always glowed when calling for heat AND it still read in SPEC.. when cold.. as it heated and cooled during it's normal cycle, it must expand the crack enough to finally either short it out or change the resistance enough so the gas solenoids wouldn't open..  when cooled off, everything back in spec.. got a new igniter for $26, installed and so far no problems..  I won't be convinced for a week or so of course.. if things work that long, I'll mark solved..   Thanks for the suggestions everyone..

[JWWebster]

Many thanks for posting that vital info KA.