Bosch Dryer won't run more than couple of seconds.

[tgoods]

I don't get a chance to work on many Bosch dryers.  WTMC3321US/03.  No matter where you set it, it shows 20 minutes on the display.  Press start and it will only run for a couple of seconds. I tested both thermistors and they seemed to be within spec. It is intermittent and was running properly when I left.  What do you think, the control board or one of the thermistors? Schematic.

[tgoods]

Went back with both thermistors and the control board today.  It was actually working worse than the first time I looked at it so it was much easier to diagnose.  I could jiggle the cycle selector knob and get the display to flicker between the correct time and 20 minutes.  I pulled out the control board and resoldered all the selector switch connections.  Put it back together and now it works great.  Saved my customer the cost of a $300 control board so, needless to say, they were very happy.

[AJ]

 

[krazytech]

Cool. where the connectors loose or burnt? did you add solder or just heat them up and let the old solder flow?

[JWWebster]

Can you post some photos? Never even seen a Bosch appliance.

[tgoods]

There were 9 connections and all but one were redundant. So I'm sure the one lone one was the cracked joint. I lost my magnifying glass so I couldn't tell by looking at it.  I used a soldering iron and added a little extra solder.  I've heard of using a heat gun to reflow the solder, haven't tried that myself.  No pics, sorry.

[krazytech]

I had a Frigidaire dryer that was doing the same thing.. Removed to control and the main relay was melted. Replaced the control and it's all good.