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Battery Cables for the CJ-3A

It is difficult to find a CJ-3A that still has the original battery cables intact. They seem to be another part of an old Jeep that doesn't last as long as the remainder of the vehicle. Much of the dislike for 6 volt electrical systems probably stems from slow cranking, which is usually due to bad connections and improperly sized battery cables. It is important, on a 6 volt system, to use the correct wire gauge size when replacing battery cables. Most modern replacement cables are thinner in diameter and can't handle the higher current draw of the 6 volt electrical systems. Dirty and rusted connections compound the problem by causing enough of a voltage drop to create a no start condition.

Positive Battery Cable
Willys parts group 15-18A is where battery cables are found in the manuals. Apparently three different positive cables were used on the CJ-3A. There are two entries in the 1949 CJ-2A & CJ-3A Parts List for CJ-3A positive battery cables. The first cable, part number 648098, is 23 inches long. There is a note stating that part number 648696 should be used in place of the first number. The length of this second cable is not shown. According to the 1955 Master Parts List the positive cable changed to a third part number, 800521, after vehicle serial number (CJ-3A) 42448. This serial number falls early in the 1950 model year. Keith Buckley was kind enough to look up the specifications for part number 800521 in a posting on the G503 Forums. The length from the center of the lug, to the center of the terminal is 22.5 inches for factory installed cables. Service replacement cables from Willys parts departments with the same part number were 23 inches long until 10/29/65 when this same cable was changed to 27 inches long. Early positive cables used cloth covered insulation which drys out and rots over time leaving the cable bare. This is most likely the reason it's so hard to find original positive battery cables still in use.

Negative Battery Cable
The 1949 CJ-2A & CJ-3A Parts List and the 1955 Master Parts List both show the negative cable as "640257 Strap, battery ground". Again the length is not given but the measured length of an original 1950 negative battery cable is 14 inches from center to center of the terminals. There is no insulation covering the wire on this cable. The negative cable is bolted to the vehicle frame on the front of the battery box support just behind the grille. It is attached to the frame with a 3/8" bolt and two internal/external toothed lock washers to ensure a good ground.

A good example of original cables can be seen on Joe Caprio’s 1951 CJ-3A at The CJ-3B Page. Click on the image for the full size CJ-3B Page photo.

Joe Caprio's CJ-3A

Since this is a 1951 CJ-3A these cables should be part numbers 800521 positive “Cable” and 640257 negative “Strap”

Engine Ground Strap
A-1098 Strap, engine ground is an often overlooked, but very important part of the ground circuit. The flat uninsulated strap provides an electrical connection across the rubber motor mounts. It is located between the vehicle frame and engine front plate at the right front motor mount.  Two internal/external toothed lock washers are used with the bolts at each end of the strap to provide a better electrical connection. The front plate bolt and toothed lock washers are 3/8" diameter and the motor mount bolt and toothed washers are 5/16" diameter. The parts manuals do not indicate the length of this strap. The measured length of several original straps varies slightly with the average being about 7 inches long.

Reproduction Cables
Vintage Wiring of Maine  can supply accurate reproduction battery cables for early CJs. The photo below shows reproduction positive and negative cables with an original 1950 negative cable. Also shown is the 3/8" diameter bolt, nut, and internal/external toothed lock washers used to attach the negative cable to the vehicle frame.

Close siblings to the CJ-3A shared some common parts. The parts books indicate that the CJ-2A and CJ-3B used the same negative cable and ground strap as the CJ-3A. The CJV-35/U, a modified CJ-3A produced for the USMC, used the same cables as the late CJ-3A.

More information about battery cables is always welcome. Click here for contact information.

Bob Westerman
3/06 - 4/19

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