Posted: Thu Apr 05, 2018 7:28 pm Post subject: Need advice on electrical system grounds
Hello, my jeep is an early 1952 M38. I'm getting ready to install the the new wiring harness. I have a couple electrical system questions but I'll give you some background on the jeep to assist in your responses.
A previous owner removed the M38's electrical system, replaced it with 6 volt items, and converted it to key start.
I had the 6 volt generator and starter rebuilt to 12 volt. I will be using a CJ3A wiring harness from Walck's with the addition of provisions for key start and turn signals.
The engine compartment's battery tray was removed at some point in it's life so I'll be using the cowl battery box for a 12 volt battery. On to the questions.
1. I know the military jeeps had a lot of ground straps for radio reception, but where do I need to place ground straps to just have a functioning electrical system?
2. Where is a good location to ground the negative battery cable that will be coming from the cowl battery box?
Two ground straps minimum, One from the engine block to the frame and one from the engine block to the body. These don't have to be the big heavy type that is sometimes used on the battery negative, find some that are between 1/4" and 3/8" wide. If you can't find them, use #10 or #8 stranded wire.
Put the heavy ground cable from the battery to one of the mounting bolts for the starter.
Good to go! _________________ '52 Dodge M37, '42 GPW, '48 FrankenJeep CJ2A/M38, '50 CJV-35(U), '51 M38, '42 WC-57 Command Car, '44 WC-51 Weapons , (2) M1941 Sperry 60" Anti-Aircraft Searchlights, John Deere M-gator, '44 White M3A1 Scout Car
All those Grounds on the old radio jeeps were for preventing static in the radios. They were not there to improve the electrical performance of the electrical system. The M38 electrical system will function just fine so long as you follow the standard protocols of wiring.
Quote:
1. I know the military jeeps had a lot of ground straps for radio reception, but where do I need to place ground straps to just have a functioning electrical system?
The M38 does very well with the one standard ground strap on the right front engine mount.
2. Where is a good location to ground the negative battery cable that will be coming from the cowl battery box?
The best convenient choice there is the standard 24V regulator mount plate. 2nd choice is the front mount bolt for the starter.
The engine to frame ground strap.
Your single cowl box 12V battery ground can be located here.
I do recommend attaching two non-standard ground jumper straps. One from the instrument cluster panel to the firewall and one from the gas tank to the tub. Otherwise just do some Google research on how to provide good grounds in an electrical system and follow their advice. That advice is usually to simply insure that all terminal connections are, clean, paint free and not corroded. This same principal applies to mounting fasteners that must carry an electrical ground, clean, unpainted and no corrosion. Adding a ground strap from the tub to frame can be helpful especially when the many bolted connections between the tub & frame are loose, dirty or corroded.
mdainsd & Wes, thanks! That is exactly what I needed. I'm about 85 % done a full rebuild on this jeep and the electrical system is the last major system that needs to be installed.
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