I did make my way out to the shop to check a couple of things earlier Saturday morning before it got too warm.
During the last trip we had been running the 10kw Onan generator on our coach to power the roof airs and when we stopped for fuel we kept the genny and A/C's running. When I started the main engine of the coach the RPM dropped on the generator momentarily causing the rooftop A/C units to drop off and then come back. I immediately thought maybe a ground issue because the Cummins diesel engine and the Onan generator share a ground at the back near the battery bank.
I performed a voltage drop test while cranking and it seemed ok with only about a 78 mV (.078 volt) drop between the battery negative and the engine block. But with the grounding stud so easy to access I thought I'd clean it up anyways.
The cable lugs and the nut were in pretty good condition but just took a wire wheel to them while they were apart.
That's a little better.
Lugs and nut reassembled. I then applied a little black paint over the connection to prevent future corrosion.
and retested. A little better with only 39mV drop (.039 volt). Not sure it will get much better than that.
However, knowing this wasn't enough to create enough of a voltage drop I thought I'd test the positive while it was also right there and easy to access. I had nearly 750mV (.750 volt) between the battery positive and the starter motor so I worked my way back to determine where the high resistance was and bingo, found it. I put my test leads across the Cole Hersee master switch.
And read 677 mV (.677 volt) right at the master switch. There's the issue.
After some research I was able to locate a new rotary switch which should be here sometime this week for replacement.
With the feeling of getting at least something accomplished, I was about to close up the shop and head inside when I remembered to take a look at my secondary water filtration. During my morning coffee I noticed my couple of dry spots really aren't getting much better even after bumping my timer a little more to each zone. I thought maybe I had a filter getting clogged.
Sure enough.
Removed and cleaned.
Reassembled and hoping that helps.
Thanks for looking.