Bob, Welcome to irv2
You should check your other half of your battery ckt. "GND" its something that alot of us overlook. The gnd will be connected to the frame of your chassis, from the battery, an your converter. you could have a loose an dirty connection. If its loose use a star washer when you remake the connection an clean the cable connection an protect with some di-elect grease. If you click on my posts bottom left you will find more information on gnd's an where you will find alot of them, there is quite a few of them, I have reminded everyone, nows a good time to check them because vibrations will loosen connections an salts on road will corrode them. While your at it check your fuse panels for loose supply wires an ckt connections.