Hi Gus, Some questions/points to consider (not necessarily in any order): 1) Is there a chance that your 500 ohm resistor got damaged somehow and is really a much higher resistance, so that it caused the SSR to turn on only partially? 2) How frequently are you switching this SSR on and off? 3) Check your 12VDC power supply to make sure that it is still outputting 12VDC and that it is fairly ripple-free under load. 4) Check the microswitch for low resistance when closed. 5) Is there anything else in the appliance controlling the heating element (thermostat, heat intensity control, etc.)? 6) How much current does the dryer heating element draw? 7) The datasheet I found online for this part says that it has a 1.6V on-state voltage drop. That's 40 Watts at 25 Amps. 40 Watts would definitely need a very good heatsink, well-bonded to the part, for something this size. 8) This appears to have zero-voltage-crossing turn-on. That is optimal for resistive and capacitive loads but NOT for inductive loads. The problem is that it always starts with voltage and current in-phase, so there is a transient until they establish the proper phase relationship. If your heating element has a large inductive reactance at 60Hz compared to its resistance, then this could cause overstress to the SSR at start-up. Sean On Tue, Dec 16, 2014 at 8:52 PM, NOPE9 YES wrote: > > Here are photos of the SSR > https://www.flickr.com/photos/48808176@N08/sets/72157649733342556/ > > The FOTEK SSR-25DA was switching power to a clothes dryer heating element > at 240VAC. > 12VDC was supplied to the + side of the relay input through a 500 ohm > resistor. A micro-switch ( normally open ) > grounded the + side to shut off the heating element. > > Is the FOTEK likely to be counterfeit ? > Although it is hard to tell in the photos , it appears the heatsink got > very hot. I had it screwed to the metal frame of the appliance. I did n= ot > fasten it tightly or use thermal paste. > > I tried the SSR on the bench ( using 120VAC and a 200W lamp ) and it stil= l > appears to work. > > Does the PIClist have any suggestions ? > > Gus in Denver > > > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .