Joined: Feb 25, 2006 Posts: 344 Location: Wichita, KS
Posted: Sun Jul 25, 2021 5:02 pm Post subject: Question about testing new wiring harness
So I am slowly nearly the end of the restoration of my 1952 M38. The engine is out at the rebuilders and I have installed a new wiring harness. Is it possible to test the hook-ups of this harness while I am waiting on the engine? I was thinking I could jump 24v from another jeep to the #10 post of the regulator harness and to a ground to power the master light switch to check lights, horn, etc. Or is there another way to do it?
Thanks,
Kendall _________________ 1951 M38
1952 M38
1952 M38A1
1942 Dodge WC-55
1951 M100 trailer
1942 Ben Hur trailer
Curious! The missing engine has no real impact on operating the rest of the electrical system. Where are your batteries? _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Feb 25, 2006 Posts: 344 Location: Wichita, KS
Posted: Sun Jul 25, 2021 8:16 pm Post subject:
Correct, but without the engine I don't have the generator, starter, distributor nor regulator connected to the electrical system. This jeep was 12v and that battery is dead and am waiting for the engine to get completed before I buy two new batteries. _________________ 1951 M38
1952 M38
1952 M38A1
1942 Dodge WC-55
1951 M100 trailer
1942 Ben Hur trailer
Joined: Oct 02, 2014 Posts: 1909 Location: South Carolina, Dorchester County
Posted: Sun Jul 25, 2021 9:57 pm Post subject:
Hi Kendall,
Just curious, do you have reason to think a new harness is defective or got hooked up wrong? _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
Correct, but without the engine I don't have the generator, starter, distributor nor regulator connected to the electrical system.
Still the missing water temp sender, oil press sender, generator, starter and distributor have no real impact on pressing on with the harness installation and ops checking of circuits. You will simply ignore those three circuits until you have your engine installed. There's no reason you cannot leave the regulator connected to the firewall harness. You can check the sender wires and distributor lead for power with a voltmeter.
As for the old dead 12V battery, I would not risk another guys jeep's electrical system using it to power my harness checkout. Just disconnect his positive and chassis ground posts. Leave the short series wire connected between his batteries. then jumper just his pair of batteries to your jeep. Or just borrow two 12V batteries and hook them up to your jeep. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Feb 25, 2006 Posts: 344 Location: Wichita, KS
Posted: Mon Jul 26, 2021 11:40 am Post subject:
No reason to believe the wiring harness is defective, I built it myself (haha). With it being new (and built by myself) I just thought I should test connections and everything as the next step.
Wes, the other "guys" jeep is my other M38 so no concern, but still how do you suggest hooking up the 24v from that jeep to this jeep? Back to my original post, can I just hook the positive lead to the #10 wire and the negative lead to the frame ground?
Thanks for your help,
Kendall _________________ 1951 M38
1952 M38
1952 M38A1
1942 Dodge WC-55
1951 M100 trailer
1942 Ben Hur trailer
Perhaps I do not understand where you are right now. If I had a need to test any harness I would prefer to do it before installing the harness with low voltage source. Once I had the harness in the jeep I would prefer to have everything installed first including the battery cables and regulator for a proper and safe test environment. I cannot advise you how to connect to a partially installed harness without seeing the entire setup. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Oct 02, 2014 Posts: 1909 Location: South Carolina, Dorchester County
Posted: Tue Jul 27, 2021 8:28 pm Post subject:
Agree.
I was taught (on stuff where peoples' lives are on the line) that the first step to check out a newly installed harness (after it's been checked and double-checked that it's properly assembled and connected to everything it's supposed to be connected to) is to "ring it out". That means a continuity check, every wire, point to point. A continuity check is done without power applied using an ohm meter. It also assumes that individual components like horns and lights and analog switches have already been checked good before installing them to the harness.
You can cheat using a tone generator or a DVM that has a tone diode checker. Or the old school analog ohm meter is always good. Use a short alligator test lead on the distant end to ground it and if you get zero ohms it's a good check. If you can't connect everything you can still check the wire, but have to make certain it's isolated, meaning the connector or terminal isn't touching anything. Only after a good ringing is the harness cleared for applying power. Naturally, you have to trace and correct circuits that don't ring good according to the wiring schematic diagram.
Not sure I'd put myself through all this for a harness that I carefully built and installed myself ----> unless I knew I got seriously distracted or confused doing it.......a chance you take. Once you put power to it, it's too late to wonder if things start melting and smoking.
Good luck! _________________ Ron D.
1951 M38 Unknown Serial Number
1951 M100 Dunbar Kapple 01169903 dod 5-51
“The only good sports car that America ever made was the Jeep."
--- Enzo Ferrari
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