Baffling problem with 12V electrical system

[harvey]

I recently purchased a 1994 Dodge SMB and can use some advise. The 12V batteries (2) no longer would hold a charge so I purchased replacements. I have a peculiar situation in which only 1/2 of the system now works. What I mean is that some lights work, some don't, the refrig runs fine but the water pump has no power, etc. I have checked all fuses that I can locate and they are ok. I located the 12V master circuit breaker and have pushed the tab as instructed in the manual but nothing happens...that is to say it doesn't seem to reset or stay in. I have not had any luck locating the 50 Amp breaker under the hood, but since some of the system has juice, I doubt that's the problem. Any suggestions or ideas at this point would be most appreciated. Thanks.

[daveb]

The fastest tool I've used is one of those lighted probes you can buy in the part houses. But you have to make sure the ground wire is true. If SMB uses a dedicated ground wire to the house system you might have an open ground wire. If they use the chassis ground it would rule that out for the most part. Use a volt meter (or probe) to go from point to point but just be aware that a ground can be generated through some devices like lights which might work to a point. Actually it sounds like you said, a blown fuse or open device somewhere. You might want to look at the isolator's secondary side for a bad connection. Check all the grounds.

[harvey]

Thanks for the tip. In hunting down the problem, I think I've isolated it to the drivers side 30 AMP circuit. When I installed the new battery, I fried a few fuses because the positive battery lead was not properly protected. That problem is solved because the fuse no longer blows, but there doesn't appear to be any current flowing through. Could I possibly have damaged that circuit? I'm new to electrical issues. BTW, in testing the system the 110V works fine, but the drivers side circuit still gets no juice. Appreciate your help.