Just speaking for myself, I do my own testing before I hit the auto store. So I know what's going on. In the past, I've had auto stores lie to me. I'm not saying anybody lied to you, probably both the battery and generator needed replacing. I'm just telling you my experience. It was a new generator on my vehicle, got home, did some testing, I realized the generator wasn't working properly by the time I got home, probably a 20 mile drive from auto store. Went back to store, told them the generator wasn't working correctly. Guy put their tester on it, said yeah, it was working fine. I got out of the car, I said, "that isn't right, let me see your tester", the guy went to backing up and wouldn't let me see it. He finally admitted the generator wasn't working correctly, but, he didn't have a replacement. Needless to say, I never went back there again. It was a national brand auto store.
Ok, enough of that. Your battery and generator connections are all good?
You realize, engine cranking, all your systems get battery voltage. Engine running all your systems get generator voltage. That can be several volt difference. You may need to do some voltage drop testing on some of your systems, could be wiring circuit somewhere that's dropping voltage because of a problem?
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