Heat Pumps and Electric Heating - Electric Heat Pump/Aux heat strips

Have a 25 yr old unit..I replaced the Aux heating coils about 3 years ago...Now it seems that the fusible links with the markings "MicroTemp FD4208A5" might be bad..these resemble a diode mounted on two stak-ons housed in a non-conductive housing..my question should I be able to read continunity across the terminals?? They read open and when I jump them out the grids seem to heat normally...Are these replaceable or should I have the entire unit replaced due to its age... Thanks in advance for any guidance

25 years old, must cost a lot to run that thing.

I'd change the whole thing and cut your energy cost by 50 to 75%.

Thanks for the response...any answer to the question should i read continunity across the fusible link when its functioning properly??

That answer is yes. It's a switch that opens and closes in response to temperature. Keeps the electric heat from getting too hot. Heaters off and cool the switch should be closed.

these fusable links are a one time shot deal. They dont reset. Supco makes replacements. You will need to get the temp rating written on the side Microtemp.....?( i.e 167C) and sometimes the color of the bullet end of the resistor looking thing can be helpful. They are usually used on gas furnaces as a rollout safety switch or in stip heaters as a safety in the event the fan motor dies and it begins to overheat.