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2009 Maibu 23 LSV Ballast Pump


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Just purchased a used 2009 Malibu 23 LSV Wake Setter. Discovered that the Center Tank Drain Pump was not running. After checking for debris, I to cut the power lines for the Center Line Fill and Drain Pumps

( so I would have a known good reference) and put in quick disconnect crimp on fittings on. When I connected 12 volt power straight from the battery both pumps ran. Placing a volt meter in the power leads going

to the pump from the control panel, with the battery OFF, I measured 0 volts to each pump. As soon as I turned the battery ON, with the ignition off, I measures approx 9.7 volts going to both pumps. When the Center

tank multi-function  switch was was placed in the Fill position, I measured 12.6 volts on the power leads to the Fill Pump. When I selected Center Tank Drain, I measured approx 9.6 volts....guess that is why the pump is not running.

I also looked at the Forward Tank Fill Pump Voltages. Withe the Battery OFF, I measured 0 Volts, Battery on, I measured  0 volts, and once I selected Forward Tank Fill on the multi-function switch, I measured 12.5 volts.

1) Why would I not get 12.v to the Center Tank Drain Pump? 2) Why am I measuring approx 9.6 volts on the power cables going to the pumps as soon as I turn the battery on.


Next I measured the voltages coming out of the Fuse Box/Electrical Control Box up under the dash. For two Known Good ballast pump circuits (Right Rear Fill and Center Fill) I measured 0 volts with the battery OFF,

11.56 volts when I turned the battery on, and 12.6 volts when I turned the pump ON with the multi-Function switches.  For the Faulty/Bad Center Drain pump I measured 0 volts with the battery OFF,

10.2 volts with the battery ON, and 9.9 volts when I turned the pump on using the multi-function switch.

What inside the Fuse Box/Electrical Control Box would cause this? Some kind of relay/switch? Anybody know where I can find a schematic?


OH, andI have an Electronic Engineering/Tech Back ground.


A bit confused 


Edited by Lawrence
additional measurements taken
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I thought that the multifunction switch was the cause... scrolling up on the multifunction display, the same multifunction switch is used to control the panel lights/dimmer.

for that function the multi- function switch works properly.  I was considering, but do not where to look, for a relay of sort, that is driven by the voltages from the multifunction switch when

it is in the MLS center ballast tank position. Where would I look?




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