Replacing corroded battery cables on my 1991 Ford E350 Winnebago. I've traced the ground cable to a tie strap on the fender, but that's obviously just a routing point, not the actual termination.
Where does the battery ground cable actually terminate on these E350 chassis? Need to find the real connection point so I can clean it properly and install the replacement cable with a solid ground connection.
On 1991 E350, battery ground typically terminates at engine block near starter or frame rail under battery. The fender tie is likely a routing point - continue tracing to find actual ground bolt. Clean to bare metal and use proper gauge cable for replacement.
On your 1991 Ford E350 Winnebago, the main battery ground cable typically terminates at one of three locations: the engine block (usually on the driver's side near the starter), the frame rail behind the battery box, or a dedicated grounding stud on the firewall. Since you've traced it to a tie strap on the fender that redirects elsewhere, it's most likely going to a grounding point on the frame rail or engine block. The tie strap is just securing the cable routing - follow the actual cable beyond that point to find the true termination.
Your 1991 E350 uses a chassis grounding system where the negative battery cable creates the primary ground path for the entire electrical system. Ford typically ran the main ground cable from the battery's negative terminal along the fender well, securing it with tie straps or clips, then routing it to either the engine block or frame for the primary ground connection. What you're seeing with the tie strap on the fender is just a cable management point, not the actual grounding location.
The corrosion you're dealing with is extremely common on E350s of this vintage, especially where the cable connects to the grounding point. Moisture gets trapped in the connection over time, creating the green and white corrosion that reduces conductivity and can cause starting problems, dim lights, or intermittent electrical issues. The ground connection is just as critical as the positive connection - a poor ground can cause all sorts of mysterious electrical gremlins.
Since Winnebago modified the original Ford chassis, there's a possibility they relocated or added additional grounding points during the RV conversion process. However, the primary engine ground should still follow Ford's original routing to maintain proper electrical system function.
For this repair, you'll need a complete battery cable set specifically designed for the 1991 E350 (consult Ford parts catalog or dealer for specific OEM part numbers, or you can use quality aftermarket cables from brands like Standard Motor Products). The positive cable runs about $35-50, while the ground cable is usually $25-40. Make sure you get the correct length - E350 motorhomes sometimes use longer cables than standard E350 vans.
You'll also need basic hand tools: 10mm and 13mm wrenches or sockets for battery terminals, possibly a 15mm for frame mounting bolts, wire brushes for cleaning corrosion, sandpaper or emery cloth, dielectric grease to prevent future corrosion, and penetrating oil like PB Blaster in case the ground bolt is seized. A multimeter will help verify good connections after installation.
Consider getting battery terminal protector spray or felt washers treated with protective compound - these help prevent future corrosion at the battery posts themselves. If you're doing a complete refresh, battery post cleaners (the ones that look like small wire brushes) are invaluable for getting clean, tight connections.
Start by disconnecting the negative battery terminal first, then the positive (always negative first for safety). Follow your existing ground cable completely - don't stop at the tie strap. Look for where it actually bolts to something solid. On most 1991 E350s, you'll find it bolted to the engine block near the oil dipstick tube on the driver's side, or to a frame rail bracket behind the battery compartment. Some Winnebago conversions ground to a stud on the firewall.
Once you locate the actual ground point, remove the old cable completely. Clean the grounding surface thoroughly with a wire brush until you see bare metal - any paint, rust, or corrosion will create resistance. If it's a bolt-on connection to the frame or engine, remove the bolt entirely and clean both the bolt and the threaded hole. Apply a thin coat of dielectric grease to prevent future corrosion.
Route your new ground cable following the same path as the original, using the existing tie strap locations for support. Make sure the cable doesn't contact any sharp edges or heat sources. Connect the ground end first, torquing the bolt to about 6-10 ft-lbs for frame connections, or to manufacturer specifications (typically 6-8 ft-lbs) for engine block connections. Connect to the negative battery post last, ensuring the terminal is clean and tight.
Test your work by checking voltage drop across the ground system with a multimeter - you should see less than 0.2 volts drop from battery negative to the engine block when the starter is engaged. If you're seeing higher voltage drop, there's still resistance in the ground path that needs addressing.
While this repair is well within the capabilities of most DIY RV owners, consider professional help if you discover the ground cable has been modified extensively from the original Ford routing, or if you find multiple ground straps that you're unsure about. A qualified RV or automotive electrician can quickly trace the grounding system and identify the best connection points, especially important if Winnebago made significant electrical modifications during the conversion process.
Professional installation typically costs $150-250 including parts and labor, and ensures the job is done correctly the first time. This is particularly valuable if you're dealing with starting problems or other electrical issues that might be related to poor grounding - a technician can diagnose and address all related problems simultaneously, potentially saving you time and frustration in the long run.
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