Low voltage gremlin

[exlonghorn]

The front fill pump recently stopped working on my VLX.  Turns out that the front fill and drain pumps aren't working because they are only getting 11.5V as measured on a multimeter.  If I connect them directly to a 12V battery having 12.3V, the motor will spin.  Interesting because all the other drain and fill pumps are working.  I am also getting occasional low voltage alarms on the water, and the MaliView only shows around 10.6V on the trailer with the key turmed to ACC and the engine and stereo off.  Readings range from 11.0-13.3 while cruising.  Again interesting because any individual battery (there are 5) is reading fine (one 12V and four 6V batteries wired to produce two 12V banks) and all are being recharged adequately by the alternator.  Sounds like a grounding problem somewhere, or a bad connection...can't figure out why its only affecting the Front ballast though, and also throwing the low voltage alarms.  This is just about the worst kind of electrical gremlin.  I recently rewired the entire battery setup hoping to fix the issue, to no avail.  Suggestions on a troubleshooting approach?  Just start at the batteries and work outward from there taking readings at each connection, or trace backward from the ballast pumps?

Edited July 27, 2016 by exlonghorn

[Fman]

Some ideas...

What is the voltage coming off the fuse buss?  I believe all those pumps have individual fuses for each pump.  I would start at the fuse buss and work towards the pump.  Your volt gauge should be reading 13.3-14.2 volts while engine is running,  11.0 is way too low, I would guess the alternator is beginning to fail or is defective.  Just out of curiosity, does the front fill pump work when the engine is running?  Another item I would check is to make sure the drain and fill pumps are cleaned out , they can get debris in them causing them not to spin easily/bind up.

[shawndoggy]

Measured with a multimeter, what is voltage of batteries when running and at rest? What is output voltage of alternator (measured at the alternator with multimeter) when running?