I’m helping a friend with an electrical problem on his “84 Chey van / motor home. At first looks like it’s not charging, but all the alternator tests prove that there is not an open circuit and when I isolate the system, it will get up to 13.8VDC. But here is where it starts to get weird, when we increase the RPM (from idle to 1200-1500 RPM) the voltage decreases and just starts draining the battery. As I stated, it’s a motor home, w/ a dual battery system (has the isolator) and when every thing is disconnected from battery #2, the out put of the isolator is almost 14V (13.8). But when we put any load / drain on the system (lights, wipers, heater, etc.) it just starts to drain the battery. Other important facts: 2 new batteries, new alternator (72 amp), and the engine was recently rebuilt, and reinstalled by a reputable shop, and they claim that they didn’t do any thing to the vehicle.
Long story short, why is it acting backwards?
Mark (A.K.A. Z28 Mark)