We have a DV350AEP/XAA dryer, S/N <HIDDEN>. It runs a complete drying cycle in manual timed or automatic mode but the heat never turns off and it "freezes" at 1 minute in the cooling cycle with the heater still running. If we forget it for too long it will stop on an HE error.
I have replaced the main PCB with a used one thinking that is where the control relays are, I also had a spare, used control board (with the buttons) and neither of those fixed it. I also replaced the moisture sensor module with a new one. I can't find a service manual beyond a 7 page quick diagnostic so I can't really figure out where the timing for the different cycles "lives" to know what I might need to look at. It would be really odd if the used main PCB or control board somehow had the same error as my old one but I am beginning to think that is it. I had a new one on order but the post office still can't find it so I bought the used one on E-bay hoping that would fix it.
I entered test mode and can see the moisture sensor "hits", they start at 500-600 with wet clothes and go down to 0 when dry.
I measured the thermistor resistance at 1.5ohm, if I unplug it with the unit running it will stop with an error code "tO", it doesn't show an error for the thermistor otherwise so I am pretty sure that is working properly. Neither main PCB will take the button combination to enter the test mode for seeing the thermistor temperature though.
I have measured both main PCB boards' heater relay and they are both working, they are open (heat off) until the dryer cycle starts, the drum motor relay turns the drum on and then the heater relay closes. It just never gets a signal to turn off again.
Saw a note from a customer on an appliance parts site about a dirty thermistor. That was it. You have to take the covers off the fan to get to it, it is really buried up in the exhaust duct. Ours had a big wad of lint hung on it. Not sure how to replace the thermistor so I am glad it is all working now.
