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Old 03-27-2023, 07:11 PM   #1
Senior Member
Brand: Thor Motor Coach
Model: Tellaro 20L
State: North Carolina
Posts: 279
THOR #26907
Mastervolt Combi 3000 Remote Inverter Switch Install

Having discovered that turning off the inverter from the Mastervolt Combi "Box" instead of from the Mastervolt Display saves about 1.5 a/h of battery power decided to install a remote switch to keep from having to pull up a panel underneath the bed to access the box.

Installing the switch took about one hour and parts from Amazon were $8.

The procedure is to remove the mastervolt cover using a small phillips head screwdriver. The cover is the same that allows access to the "dip" switches.
Locate the remote small screws that are located below the green Mastervolt "telephone" style connectors. On mine there was one green wire and one "Blank" connector plugged in there. You can see those connectors in the first photo located near the Thor "rats nest " of wires. I unplugged those after removing power to the inverter using a master switch previously installed also visible in the same photo. I am honestly not sure if power needs to be removed prior to doing this but since I had the ability to do it simply figured it was not a bad idea. There is a small green connector below these plugs that has very small screws that can be removed by gently pulling (unplugging) out the entire assembly. It is much easier just to remove this assembly rather than try and remove the jumper and install the wires while it is plugged in. There is a "jumper" on the top two screws that needs to be removed if installing the remote switch.
Then simply attach two 20 gauge wires to the same location where the jumper was located and reinstall. The small red and white wires in the first photo are the ones that attach to the back of the combi where the jumper was. Then attach the two other ends of the wires to the switch purchased and locate it anywhere you choose. The switch on the Mastervolt Combi will remain on at all times but the new switch just installed will turn the inverter on and off as desired effectively "mimicking" the switch on the box. I installed the switch close to the access panel near the bathroom door but it can be located anywhere you want.

After installing this I will probably not use the inverter display panel to turn it on or off anymore. The function is the same but it consumes more power when turning the inverter off from the remote display and have found it to be more of a "challenge" to manipulate. I have noticed that when turning the switch off from the box ( or new remote switch) it also turns the Mastervolt Display completely off but that is not a problem for me.

A wiring diagram from Mastervolt for this modification is shown in the instructions for the Mastervolt Combi.
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