Grounding issue...?

[SeaFever]

Hi All,

When I visited the boat after a couple of months today (Note my boat is a Pearson 10M) and tried to turn on the bilge pump to pump the water out here is what I found:

-- The bilge pump was running but was barely audible (Less sound than usual)
-- No water was coming out even after running the pump for a few minutes
-- Tried with the 2nd battery, same result
-- Thinking that there was a problem with the switch panel (rule model 41) opened it up and checked everything to be ok.
-- Checked battery voltage and found to be in normal limits.

Then thinking that this troubleshooting was going to take time I turned on the stereo to entertain myself in the interim. Here is what I found then:

-- Again turned on the bilge pump and the stereo volume went down to zero.
-- Switching off the bilge pump brings back the stereo volume
-- Same thing happens with the fresh water pump. Turning on the fresh water pump takes the stereo volume to zero, turning it off restores the stereo output!

I was perplexed. The battery cannot be that much out of juice that it cannot provide required current to these two devices!

Then I said let me check if the battery can turn the engine on. Lo and behold the engine started with the first crank! So I surmised that the batteries are fine. At least enough to not give me the problem I was having.

So where was the problem? After thinking about it for a bit, I think it is a grounding issue. Somehow, as soon as I am turning on an appliance that drains some significant current the ground is breaking. What do you guys think?

I did take pains to do the proper grounding when I re-powered with the Universal diesel engine last year. With advice from Stu I put in a grounding bus and terminated the engine ground and the negatives of both batteries to the bus. Also connected the other ground wires to it. I did not have any problems until now. It was just this time that I had this issue.

Anyone faced a problem like this before? Any suggestions on how to troubleshoot and find where the root cause is coming from?

[2ndwish]

Mahedra- It sounds like a bad cable connection either in a hot or ground wire. If you followed Stu's advice, you have a complete wiring diagram of the system.  You know that the starting circuit voltage is good, and the circuit with the bilge pump has a big voltage drop (due to a resistive connection). If it were me, I would study the wiring diagram to find where the drop might be occurring and feel which connections are warm. You could also get a multimeter and measure the voltage (measured between the power and return lugs) at the different points in the circuit, maybe starting at the bilge pump and working back towards the battery, which you know to be good. You can also gain clues from the diagram by figuring out which parts share circuit wires (like your stereo and bilge pump) and switch additional parts on and off which share wires from a split point closer to the battery. You will eventually find the bad connection. Good luck.
T

[SeaFever]

Thanks T,

I agree the only way to solve this issue is going to be tedious tracing back from the bilge pump towards the batteries. I is just interesting that an issue crops up after a year of re-power...I am also wondering of the high level of water submerged some wiring which was short-circuiting the current. I used the manual pump to pump out the water and the bilge will be reasonably dry for the next few days. I plan to go back to the boat in 3-4 days for checking troubleshooting. Will report back what I find. Cheers for now.