Where can I get wiring and plumbing diagrams for my older RV?

Dear Dave, 
Do you know where I can find wiring and plumbing diagrams for my older motorhome? I contacted Thor and they replied that they only have those for everything 2010 and forward. —Wes, 2007 Four Winds 35B

Dear Wes,
Getting wiring diagrams and plumbing schematics for RVs has been a challenge for years. Most have a “generic” plan that the workers reference. However, as the unit goes down the line, there is quite a bit of variation in installation and very little documentation.

Wiring diagrams

Even when you do get somewhat of a wiring diagram, it’s not worth much as it doesn’t show where the wiring is, what color it is, or the gauge. Here is what I got from Thor on a 2016 Challenger:

It looks fairly well documented; however, if you actually try to follow the wires you can’t! We were looking for the converter to swap out a Progressive Dynamics lithium profile model and it was not listed anywhere on this diagram. Even talking with the technical support did not help as nobody knew where it was located and no documentation. The tech even went to the line and asked several employees and got about five different answers!

We finally found it by listening for the distinctive hum with everything else off. We had to remove the mattress, the access panel on the top of the bed platform, and way back underneath, covered in wires, was the converter.

Here is the new Progressive Dynamics converter “nestled” in the wires. We did not dare rewire the mess as none of this showed up on the wiring diagram we were sent.

And, this mess in the battery compartment was not highlighted on the diagram either.

Unfortunately, this is a common practice due to the “race to the bottom” we have discussed often. Wiring diagrams cost money; designing specific wiring looms costs money. Taking the time to neatly secure wires in an application also costs money.

Wiring nightmares

Here are a couple of other wiring nightmares that readers have sent in.

How would you show this in a wiring diagram? What happens is the units go down the line or from stall to stall and the first line worker putting in an appliance or electrical component pulls a length of wire to install it. With several different lengths and floorplans, the appliances and electrical components are in different locations. So there is excess wire and it just gets “bundled” and tucked inside compartments.

When we first started shooting video for the RV Repair Club, we used a 2017 high-end toy hauler that belonged to a friend of mine who was a certified and bonded electrician. We started removing drawers and panels to gain access to plumbing and electrical components and saw this very same wiring. His reaction was: “This isn’t to code!”

Where do you get wiring diagrams?

To answer your question, they most likely do not exist, as Thor indicated. However, what you can possibly is find the wiring diagram for specific components that original equipment manufacturers (OEM) provided. Those would include things such as the water heater, distribution center/converter (DC), and other components. You would at least have a starting point.

You can identify the wiring that the OEM has provided and possibly trace that back to the DC. 120-volt wiring will use 3-wire Romex similar to residential wiring. Therefore, you can start at the DC with the circuit breakers and try to trace to the roof air, outlets, and other components.

Tool to trace wiring

A good tool to help trace wiring is this wire tracer aka cable tracker, available on Amazon here.

If you have been following my posts, you will have come across several that have highlighted Winnebago’s wiring, plumbing, and 3D drawings which they have been providing for many years. That type of documentation takes an enormous amount of time, which is an enormous amount of money. That is one of the reasons that the Winnebago product is more expensive. However, too many people just assume they are all built like cars and trucks and look at price alone.

We ran into the same issue working on the “Trailer From Hell”—a 1996 Forest River Salem that had extensive water damage. We gutted the front and rear to fix the damage and retro the unit. Wires were going everywhere and we decided to install a new DC, as the converter was shot on the old one. Instead of trying to trace the rat’s nest of wiring, we just ran new wires for components we could not identify.

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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

Read more from Dave here. 

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