New front harness, flat batteries

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Fil Bonica
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Re: New front harness, flat batteries

Unread post by Fil Bonica » July 14th, 2018, 9:21 pm

If you want or need on site help
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Re: New front harness, flat batteries

Unread post by rickf » July 14th, 2018, 10:54 pm

TraceL wrote:I’ll admit, I am thoroughly confused. I went through and disconnected the entire harness. I am going to reinstall it, checking for the draw after each system is hooked up. I’m fairly convinced that the harness itself has an issue. It was NOS, but I’m sure there are cheap knockoffs out there. Is there a list of what number wires go to which connections? I was hoping to find a step by step installation instruction. I am 95% sure it was installed correctly but obviously something is amiss.
https://olive-drab.com/od_mseries_circuits.php
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: New front harness, flat batteries

Unread post by Hambone » July 15th, 2018, 8:41 pm

TraceL wrote:I’ll admit, I am thoroughly confused. I went through and disconnected the entire harness. I am going to reinstall it, checking for the draw after each system is hooked up. I’m fairly convinced that the harness itself has an issue. It was NOS, but I’m sure there are cheap knockoffs out there. Is there a list of what number wires go to which connections? I was hoping to find a step by step installation instruction. I am 95% sure it was installed correctly but obviously something is amiss.
Sorry for the confusion, electrical problems don't just jump out at you unless there is smoke, and we don't want that. I'm sure your harness is NOS, no Chinese ones available, the electrical connection chart that Rick provided is great for quick reference, be patient, use dielectric grease on the connections, makes them easy to plug and unplug. Reinstall one circuit at a time with your meter hooked up, something should show up, here to help anyway I can.

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Re: New front harness, flat batteries

Unread post by rickf » July 15th, 2018, 9:39 pm

Here is a diagram of the wire harness for the A1 with the 60 amp alternator and also the 100 amp option. This has all of the wire numbers on it. NOTE! This is not the standard 25 amp setup.

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1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: New front harness, flat batteries

Unread post by Mark » July 15th, 2018, 10:29 pm

Instead of dielectric grease for the plug connections I used lucas green wheel bearing grease
mark


1968 m274A5
1960 m151
1981 m151A2
1964 m416
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Fil Bonica
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Re: New front harness, flat batteries

Unread post by Fil Bonica » July 16th, 2018, 11:13 am

It is more important to refer to an A2 harness rather than just an A1.
You need to reference both to make the proper adjustment from one to another:
Especially for lighting differences and the whole electrical fuel pump wiring if he is still using it.
This may be moot if he is using a mechanical pump.
Just some obvious things that come to mind.

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Re: New front harness, flat batteries

Unread post by TraceL » July 18th, 2018, 10:12 am

So I began disconnecting everything starting under the hood. I tested for the draw every time I unhooked a connection. Nothing changed. Still a 26 volt reading. I then moved to the driver side under the dash. I disconnected everything except the starter switch. No change. Once I pulled the gauges out however, I had a change. For some reason when I disconnect the oil pressure gauge, the draw goes from 26 volts to -22 volts. I’m not an electrical guy so I don’t know if this is significant or not.
1962 M151

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Re: New front harness, flat batteries

Unread post by TraceL » July 18th, 2018, 10:31 am

I have completely disconnected the front harness except the starter switch, and I am left with a -22 volt draw. Is it safe to assume the starter switch is the culprit? If it is, I’m left wondering why the oil pressure and fuel gauges move when the batteries get hooked up and the on/off is off. And why the headlights and taillights pulsate with the volt meter when running. I can’t imagine this is all connected to a bad starter switch.
1962 M151

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Re: New front harness, flat batteries

Unread post by Fil Bonica » July 18th, 2018, 11:01 am

Trace # 27 wire is somehow getting power.
That is the feed for the instruments that should come from the ignition switch.
Start poking around there.
A negative reading your’e getting is erroneous.
Typically only means an open in a digital meter.

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Re: New front harness, flat batteries

Unread post by TraceL » July 18th, 2018, 11:41 am

I just installed another starter switch and connected the harness power #5 to it. I’m not longer getting sparks when I connect the batteries. Hopefully that means I found the draw. As for the #27 power getting to the gauges somehow, I’ll keep you posted.
1962 M151

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Re: New front harness, flat batteries

Unread post by Fil Bonica » July 18th, 2018, 12:03 pm

Is the battery lead connected to the battery?
Is the wire from the load side of the switch connected to the starter as it should?

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Re: New front harness, flat batteries

Unread post by TraceL » July 18th, 2018, 12:08 pm

Yes. Both the battery lead and the cable going to the starter are connected. Also the #5 power to the harness is connected.
1962 M151

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Re: New front harness, flat batteries

Unread post by Fil Bonica » July 18th, 2018, 12:12 pm

Is the other side of number 5 connected to the alternator?

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Re: New front harness, flat batteries

Unread post by TraceL » July 18th, 2018, 12:20 pm

It is not.
1962 M151

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Re: New front harness, flat batteries

Unread post by Fil Bonica » July 18th, 2018, 12:45 pm

Then there is no power to the harness.
Connect it at the alternator and watch for sparking.
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