How to Identify Unknown RV Parts: Complete Guide for Used RV Owners

The Rundown

Finding unfamiliar parts in a new-to-you diesel pusher is one of the most common surprises of RV ownership. Previous owners stash spare parts, specialty tools, and leftover repair components in storage bays and the engine compartment for years, and plenty of them get left behind at sale time. The good news is that you can almost always identify a mystery part yourself by working through a few clues — where you found it, its size and material, and any markings or part numbers. This guide walks through that process and points you to the fastest ways to get a positive ID.

Start by documenting each item in detail — its size, color, material (plastic, metal, rubber), any markings or part numbers, and exactly where you found it in the coach. Common mystery items in diesel pushers include spare parts like valve caps, electrical connectors, plumbing fittings, or specialized tools for maintenance tasks.

Why It Happens

Previous RV owners often accumulate spare parts and specialty items over years of ownership, and these sometimes get left behind during a sale. Diesel pushers especially tend to have unique components that aren't found in regular vehicles - things like air brake system parts, engine compartment access tools, or specialized plumbing fittings for the various systems.

Many experienced RVers also carry backup parts for common failure points, or they might have started a repair project and left the parts behind. Some items might be aftermarket accessories or modifications that the previous owner installed. The location where you found these items can give us big clues about their purpose - engine compartment finds are usually mechanical parts, while items in storage bays might be plumbing or electrical components.

Gather These Items

To help identify your mystery items, you'll want to gather some information and tools:

• A good flashlight or headlamp for detailed examination
• Reading glasses or magnifying glass to check for part numbers or markings
• Camera or smartphone to take clear photos from multiple angles
• Measuring tape or ruler to document size and dimensions
• Your RV's manual and any documentation left by the previous owner
• Access to RV forums or the manufacturer's parts website for comparison

The Fix

Start by examining each item carefully for any markings, part numbers, or manufacturer stamps. Even small numbers or letters can help identify the purpose. Take clear photos from multiple angles and note the exact location where you found them. Check if the items appear new or used, and look for any obvious mounting points or connection methods.

Compare the items to your RV's systems - do they look like they belong to the plumbing, electrical, or mechanical systems? Check your owner's manual for exploded diagrams of various components. Post detailed photos and descriptions on RV forums like IRV2 or Reddit's RV community, where experienced owners can often identify mystery parts quickly.

Once you have the item's size, material, markings, and location documented, you can usually match it to a system quickly — or get a fast positive ID by posting clear photos to a brand-specific forum or your chassis maker's online parts catalog, as described below.

Know Your Limits

Don't feel embarrassed about not knowing what these items are - even experienced RV technicians encounter mystery parts regularly, especially when working on different manufacturers and model years. The RV industry uses many specialized components that aren't familiar to general automotive mechanics.

If the items appear to be important mechanical or safety-related components, it's worth having them identified by a qualified RV service center. Some parts might be critical spares for systems like air brakes or engine components that you'll want to keep with the RV. When in doubt, store the items safely and label the container with where and when you found them - this information might prove valuable later during maintenance or repairs.

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