Replacing thermal fuse in wall oven power supply. Does fuse measure temperature of ambient, or, temperature based on current through fuse? I ask because I would like to attach wire leads to fuse since I screwed up soldering directly to the board. Thank you.
It just measures heat, doesn't matter where it comes from. But-
Keep in mind heating the fuse with current will heat the inside to a higher temp that just warming the outside as there is thermal resistance of the device package to overcome.
Just be careful soldering the leads and you should be ok.
Thermal fuses are supposed to open when their temperature rises above their design failure point.
Certainly if you pass too much current through it will fail! Most thermal fuses are on heat sinks or fans and open at relatively low temperatures to indicate that the fan or cooling system has failed and this helps to protect the electronics from heat failure.
Due to their sensitivity they are hard to solder without opening internally! You MUST heatsink the leads to protect the element inside the thermal fuse from getting too hot. A heatsink can be the jaws of needle nosed pliers or similar clamp with lots of metal to absorb the heat of soldering. I'm not certain that all types of thermal fuses can even be soldered - most I've seen have metal clips clamping them to the wires. You may have to experiment. You probably should get more than one in case of failure...
Pigtail screw-on clips might work fine.
John :-#)#
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Another tip is to freezer spray the body of the thermal fuse before pre-tinning the wires and then repeat freezing before soldering proper.
** Thermal fuses respond to the temperature of the case and are designed to have low self heating due to current flow. Makers specify the operating temp and also give a max continuous current rating at which self heating is not significant. ** The thermal fuses I know have wire leads and look a lot like film capacitors or diodes. What have you got ?
.... Phil
Thanks everyone! Decided to crimp on some 2" leads and thereby keep soldering heat far away from the Thermal Fuse. Your help is greatly appreciated.
Ivan-
When I've soldered a thermal fuse, I held a lead by a heavy pair of pliers next to the body. The pliers had a rubber band around the handles so my hands were free. So far there were no failures due to soldering.
Some thermal fuses are supplied with a little brass sleeve for crimping. However, it is difficult to get a good crimp between two solid wires. Be sure you crimp to a stranded wire with the solid wire in the same bundle.
Fred
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