Engine Battery Voltage Decrease

2017, 2351.  I have the toggle switch on the dash that is supposed to allow playing of dash radio without using power from engine battery. when boondocking the engine battery voltage starts to go down when playing radio.  FYI, replaced momentary switch with on/off, also now on second battery.  Any thoughts?

Where are you measuring the voltage?

When you use power, voltage goes down. I know they did some changes to how this switch works.

If it works like mine, before I switch batteries - Ford and house batteries are at a different voltage. When I turn on switch all batteries read same voltage in a few minutes.

I thought that the switch was to start the engine using the house battery. Never tried it.

I thought that the switch was to start the engine using the house battery. Never tried it.

As I understand it the switch activates a solenoid that allows the house battery to trickle charge the truck battery.  I was told it was not really designed to 'start' the truck from the house battery as the wire is too small. 

I can say that when I tried it I just blew the inline fuse at the solenoid.  Recommended process (if the truck battery is dead) is to hit the switch and then let the house battery charge the truck battery for a minimum of 20 minutes.  Then try starting the truck.

I am not sure if it has always worked this way, older models might be different.

Voltage measured at battery at battery with digital meter and in dash with a plug in digital in the cig style plug.  Measured the same.  Bogart solar monitor shows different voltages.

Also the switch I requested to be added was to allow us to listen to sat radio from house Batts without running down engine batt.  Also when I turn on the switch ( formerly momentary, now on off) it immediately brings up the voltage of engine batt. with solar providing power to house Batts.

Voltage measured at battery at battery with digital meter and in dash with a plug in digital in the cig style plug.  Measured the same.  Bogart solar monitor shows different voltages.

Also the switch I requested to be added was to allow us to listen to sat radio from house Batts without running down engine batt.  Also when I turn on the switch ( formerly momentary, now on off) it immediately brings up the voltage of engine batt. with solar providing power to house Batts.

So now I don't understand your original question. It seems like it is operating like you want. The solar is charging all batteries.

Sorry for confusion.  I have 2 switches.  One is the original switch for trickle charging engine batt fro house bank.  I replaced this momentary switch with on/off. This works fine.  PC added a second switch the purpose being to be able to listen to dash radio from house bank when boondocking so as not to discharge engine batt.  The idea being this would isolate the engine batt from radio use without turning on igntion.You would then only need to use the original trickle start switch in an emergency.  So it would seem the second added switch does not do this.  I guess I could use the trickle start switch in the "on" position when listening to radio, but that was not the plan or my understanding how it would work.

Do you have an amplified  subwoofer?
Maybe try disconnecting the truck battery and see if the radio (and subwoofer?) still works .

Just spoke with PC they also think it could be the amp wired through the Pioneer radio.