hollowell

I have a Jeep Grand Cherokee that has a intermittent charging issue. I can drive the vehicle stop it and it will not restart. My mechanic had a test light on the battery that was on when the key was in the off position and he pulled the 50 amp fuse it went off plug it in the light comes back on. Where would my open circuit be. And what does that 50 amp fuse operate.

dave1123

Welcome to CF!

IDK what vehicle you have, but you need to do a parasitic draw test on the system. Disconnect the positive battery cable and hook an ammeter between the cable and battery post. You shouldn't be drawing more than about 0.75 amps. That's for the PCM and radio memory, and the security system receiver. If you have more, start pulling fuses until it drops. One known fault may be the diode pack in the alternator. With a bad diode, it will keep the field energized with the engine off. Another fault may be the amplifier for the radio not turning off.

Some of the later jeeps have an IOD fuse (ignition off draw). This is to eliminate those circuits by pulling the fuse. With that fuse pulled your battery draw should be zero, but you'll lose the memory data stored.