Adding A Generator Start Switch


Both of our previous Class As had a generator start switch on the dash, next to the driver.  In our new Class C, it's mounted in the panel by the side entry door.  Not that it's a horrible location for when the RV is parked, but it doesn't make much sense when traveling.  If I stop for fuel, I need to shut the generator off.  The adavantage to a Class C is the driver's door makes it easy to get in/out of the RV.  But if I have to back to the side door to turn off the switch, that's an aggravation.  Some campgrounds will now bring the registration paperwork right to the RV, rather than having to go inside. Our generator and exhaust are right next to the driver's door.  I don't want to leave it running as someone is trying to talk to me.

This modification to add an additional remote start/stop switch is quite simple.  You don't need a $70 Onan brand switch.  Four wires, and a $8 switch will do the job.  You simply parallel the new switch, to the existing one. Details in the pictures below.  I am adding LiFePO4 batteries to our RV, and I'm modifying a lot of different electrical items.  The switch panel I added to my RV isn't what most people would want, but I made a similar one that should work for most applications.  The switch can be mounted anywhere, and the custom bezel makes it appear as a factory option.

The usual disclaimers apply.  This is how I modified my motorhome.  You need to check the wiring of your motorhome before proceeding.  Any damage you might do to yours, is no fault of mine.  I took the time to reserach my RV, you'll need to do the same for yours.

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Both of my previous Class A motorhomes had the generator start/stop switch on the center console, within easy reach of the driver.  It's the illuminated switch in this picture.
We now have a Class C motorhome.  Looking back from the driver's seat.  The black panel on the left is where the generator switch is located.
If you've been to Disney's Fort Wildeness, you're already familiar with the drive up booths to register.  The generator exhaust points directly at their open window, and the booth operators ask politely that the generator be shutdown.  Since the pandemic, a number of campgrounds will now bring the paperwork to the arriving RV, rather than having people congregate indoors.
With the generator switch next to the driver, you merely need to reach to shut it down.  With our current RV, I have to take off my seatbelt, and walk back to shut it down.  Dumb design.

I tried engraving and cutting the acrylic with my 40W diode laser, but it wouldn't work with the white lower layer.  The one closest was cut on a 40W CO2 laser, which operates on a different part of the light spectrum.  It has no issues with any color of acylic, including clear. Amazon Product: Trotec TroLase | 12"x24.25"x1/8", 4 Pcs. Click here to go directly to the Amazon product.

Since this switch will be paralleled with the existing, there's no limit to the number of switches that can be added, so you can put one by the bed if you so desire. Amazon Product: RV DESIGNER S341, Rocker Switch, 10 Amp, Momentary On/Off/Momentary On, SPDT, Black, DC Electrical.  Click here to go directly to the Amazon product.

The laser cuts perfect holes, any shape.  The switch simply snaps in place.

I added a waterproof connector.  This allows the cable to be disconnected, if the generator needs to be removed for repair or service.  Amazon Product: 711Pcs 43 Sets Waterproof Automotive Wire Connectors with Ratchet Open Crimping Tool. Click here to go directly to the Amazon product.

Since the generator is right behind the driver's seat, it's an easy place to reach.  I removed the step plate from inside the cab, which is only held in place with snaps.  Gentle prying and it comes right out.

On the right end of the step area, is a small existing hole.

A closer view.  Don't need to drill any holes to route a cable through here.  I did encase it with 1/4" split loom, to give it some protection. Amazon Product: 100 FT 1/4” Wire Loom Split Tubing Auto Wire Conduit Flexible Cover. Click here to go directly to the Amazon product.

I also removed the lower dash panel, which also just snaps in place.  This made routing the cable easy.

The excess cable was put on the turn signal stalk momentarily, until the rest of the cable was secured with tie wraps.  Once I was sure of the necessary length, I cut it about a foot long (service loop).

The skinny split loom in the middle of the picture is the 4 conductor cable.
Since I'm replacing the original switch and bezel, I made a panel for the two switches.

The old switch panel was removed.

It never sat flat.  Rather than use a nut and bolt, they used a metal screw, which distorted the plastic dash panel, and prevented the switch bezel from sitting flat.

I used blue painter's tape to prevent scratching of the dash, and to mark the areas needing to be drilled or cut.

Since "I" didn't install the original switch, my options are limited on placement.  There are mounts nearby that hold the panel to the dash. Looks like one of these will be compromised.

I used a step drill bit for most of the removal of plastic, and finished with a Milwaukee multi-tool.

I mounted all the components, using button head screws.

I made oversized holes so the snap in switches have the necessary clearance for their locking clips.

The new switch panel is complete.

I did have to remove some dash foam to make clearance for the new switches.  An oscillating cutter made short work.

The panel has been re-installed.  Now I need to splice into the generator control harness.

With the factory cable unplugged from the generator, I can now splice into the factory cable, with my cable.

Here's the wiring diagram I made for the Onan connector.

Here's the basic bezel I'm offering.  The switch securely snaps into the opening.

Only 3 wires are needed for the version without the LED.

The version with the LED is the same physical size as the other.

This LED has a green and black wire.  The black is the negative, the green is the +12V.

I tapped into the green/white stripe, white/blue stripe, yellow/black stripe, and the orange wires.  The switch was wired to the first three wires, and the LED was connected to the orange (positive) wire, and the green/white stripe (ground) wires.

If you're interested in one of the bezels I made, I'm offering them on my eBay account.  I have one design with an LED, and one without.  They will be offered separately, and I'll have another listing offering two (your choice of style), at a discount.


Products Used In This Project

Amazon Product: RV DESIGNER S341, Rocker Switch, 10 Amp, Momentary On/Off/Momentary On, SPDT, Black, DC Electrical.  Click here to go directly to the Amazon product.

20FT 18 Gauge Wire 4 Conductor:

Male/Female Spade Wire Crimp Connectors:

Ratcheting Wire Terminal Crimper:

5 pcs 8mm Panel Mount + 5mm LED Colored Green:

If you have a CO2 laser, and would like to make your own custom bezels, here's where I buy the laminated acrylic sheets:. Amazon Product: Trotec TroLase | 12"x24.25"x1/8", 4 Pcs. Click here to go directly to the Amazon product.


Last updated 02/23/24    All rights reserved.