I broke mine trying to fix this, but the fix is very easy. remove the out shell and you will see two prongs with contacts that engage when the plunger is pressed. The plunger will not stay down because the prongs are bent and/or dirty. clean the contact, push the prongs closer to the contact and that should do it. Becareful about how you disconnect and reconnect the wires. That is the mistake that I made, and the fuse blew. BTW, if you fix yours, please let me know what kind of fuse is on it. The fuse is in a sheet in a cluster of wires between the two plungers.