New front harness, flat batteries

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New front harness, flat batteries

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New front harness, flat batteries

Postby TraceL » June 22nd, 2018, 8:08 am

Good morning all,

I have a issue that popped up after installing a NOS a2 front harness into my 1962 M151. My 151 has basically been converted to an a2 as far as the electrical system is concerned. Electric wipers, mechanical fuel pump, 60 amp charging system, and directionals. Previously I had a pieced together A1 harness that finally failed, so I just replaced it with a NOS a2 harness. After not starting it for a week, I went to run the mutt and the batteries were completely flat. I can’t even recharge them. Before I spend the money on new batteries, where do you think the draw is coming from? Full disclosure, the old harness failed when the the system was overcharged by my previous 60 amp alternator. I replaced the alternator when I changed the harness out and I’m 99% sure everything is hooked up correctly.

Thanks for your input.
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Re: New front harness, flat batteries

Postby rickf » June 22nd, 2018, 8:14 am

My first guess would be that the batteries were damaged by the overcharging. Second guess would be that maybe the light switch was left in the dash light on position. And lastly is a possibly bad voltage regulator. You will not be able to check anything until you have new batteries and make sure they are fully charged before you do any testing. Don't just throw them in and try it. Put them on a charger and fully charge them first. Then hook up all the cables but the ground cable, make sure all the light switches are in the off position and the ignition switch is off. Then put a volt meter between the ground cable and the ground post of the battery and see if you get a reading. If you do then you have a draw. Disconnect the alternator and try again. If you still have it then post again and we will go from there.
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1984 M1008
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Re: New front harness, flat batteries

Postby Fil Bonica » June 22nd, 2018, 8:44 am

Have had the main lighr switch fail internally .
Disconnect the switch to see if any current draw goes away..
Carefully examine the wiring to make sure there arent any chafes on any cables.

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Re: New front harness, flat batteries

Postby TraceL » June 22nd, 2018, 9:29 am

Thanks guys. I will try that this weekend. I’m an 100% sure the light switch was off. I had a feeling it would be alternator related. Though I must confess that when I started installing the new harness, I forgot to disconnect the batteries. I didn’t get far because the first thing I tried to unplug was the starter switch. Once the sparks flew I quickly corrected that mistake. The mutt ran great for a few days after the install. The only thing I noticed is the voltage meter would bounce around a bit while I was driving. It wasn’t doing it consistently , and It always stayed in the green.

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Re: New front harness, flat batteries

Postby rickf » June 22nd, 2018, 9:57 am

That is usually a sign of a loose wire, Check all of your power and ground connections but the fact that the batteries went dead you need to do the tests I outlined after checking the wiring just to be sure.

Be sure you have a ground wire from the engine to the body, original location is Bell housing above starter to horn mount bolt.
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1967 M416
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Re: New front harness, flat batteries

Postby TraceL » June 30th, 2018, 9:18 pm

So, I installed two charged batteries and here is what transpired. Electrical is not my strong suit, so I apologize if I didn't preform the tasks exactly as you described. I checked all my connections, including the ground from the horn bracket to the bell housing, and hooked up the battery cables except for the ground. I then used a multimeter set to DC and place one end on the ground cable and the other on the ground post. I got a reading of 26.01. I'm guessing that means I have a draw. I then disconnected the the larger diameter cable (power cable?) going to the alternator, and tested again. No change, still 26.01. I reinstalled the power cable and tried the smaller diameter cable (Ground?) on the alternator. No change again. I then disconnected the 4 cables going to the back of the on/off switch. No change. Then tried disconnecting the light switch. No luck. The only thing I noticed is when I hooked the ground cable up to the batteries with the ignition and light switches off, both the oil pressure and fuel gauges made a clicking sound and moved counter clockwise at the same time. I'm guessing that something is sending them power even with the Mutt turned off. Not sure where to go from here.
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Re: New front harness, flat batteries

Postby rickf » July 1st, 2018, 9:55 am

Ok, You did all the tests correctly and you are correct, you have a draw, Why and where is the problem. If you touch the ground cable to the battery you will probably get a spark, the size of the spark will give some sort of indication of what we are dealing with. It could be a light bulb Very small spark) or a direct short( quite large spark). All you need to do is tap the cable to the terminal, that way if it is a direct short your natural reaction will be to pull back quickly and no harm will be done. If it seems that nothing has happened then you will need to darken the area and look closely for a spark. If you are handy with a soldering iron then you can solder a wire to the center pin of a 24 volt tail light and another to the side case of the bulb and you have a test light. This is a good indicator of whether the draw is pulling enough amperage to light a small bulb.
Somewhere I read where somebody had an issue like this and after many hours of testing they found that the pins were reversed in on of the plugs in a brand new harness! If you unscrew and remove the connector off of the light switch and you also remove the wires from the ignition switch then "technically" there is no way there can be a draw since you have eliminated both switches for power out of the system. At that point leave those two things disconnected, leave the meter connected so you do not have to keep attaching it, and then start disconnecting things one at a time until you find the offending item. Whatever it is I am going to bet it leads to a wiring issue in the harness.
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1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: New front harness, flat batteries

Postby Fil Bonica » July 1st, 2018, 10:26 am

Trace:
With the ignition switch off there should be no power to the instrument cluster.
There are two number 11 wires going to the ignition switch and two other wires .
I goes to the instrument cluster and the othet to ignition coil.
Typically the 11 wires go to A&C of the switch and the other two to B&D.
Make sure they are correct.
If not you could have a current draw right there.
By any chance is the clicking sound a breaker tripping?
That could be an indicator of another kind if problem.
Hope this helps and doesnt confuse the issue for you.

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Re: New front harness, flat batteries

Postby TraceL » July 10th, 2018, 3:57 pm

I have been sporadicly unplugging systems and testing for the draw. So far I have had no luck. I tried changing position of the wires on the the on/off switch, but it didn't help. I just got a new one in the mail, along with a new brake light switch. The current A1 switch was fried when the old alternator overcharged the system. Hopefully the A2 to A1 brake lithe switch adapter I made works. I have heard that you can't just use an A2 switch with the A1 pedal assembly. I also bought a new circuit breaker. I think that clicking sound may be coming from one of the ones in the dash, like Fil suggested. Its either that, or the two gauges that activating when i hook the ground cable up. The spark isn't very big or bright when I go to connect it. Hopefully I will be able to spend some quality time on it this weekend and get closer to an answer.
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Re: New front harness, flat batteries

Postby rickf » July 10th, 2018, 6:04 pm

A brake light switch is nothing more than a on-off switch, no matter whether it is hydraulically controlled like the A1 or mechanically controlled like the A2. As long as one way is on and the other is off it will work. Are you disconnecting items as I said and leaving them off as you go along? especially leaving the light switch AND ignition switch completely disconnected? If you are not doing that then you are chasing your tail.
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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

Postby TraceL » July 11th, 2018, 8:58 am

Oh, I’m afraid I missed that part of your responses... after I unplugged and checked for a reading, I’ve been pluggeing the part back in and moving onto the next part. Well, that may explain why I haven’t found the issue yet.
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Re: New front harness, flat batteries

Postby Hambone » July 11th, 2018, 9:32 am

Those electrical gremlins are a PITA, process of elimination is the best way, clean all ground points as you go, too bad we can't just plug into a computer. :roll: I have seen in the past where the starter switch can build up carbon to create a draw.
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Re: New front harness, flat batteries

Postby rickf » July 11th, 2018, 10:42 am

And you would not believe how many times I have schooled dealer mechanic on how a computer AND the one checking it can be fooled by a bad ground. All it takes on a newer car is a couple ohms resistance on the PCM ground to unilaterally throw off the whole system but because the ground is the main focal point for the PCM it shows that all is fine. So do NOT believe everything they tell you when they say your car is fine just because it has no codes. The codes are only present when the computer sees something wrong. If it can't see the problem it can't report it. And THAT is where good old fashioned step by step, graduated troubleshooting comes in.
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

Postby TraceL » July 12th, 2018, 4:15 pm

Update:

I continued to unplug (and leave unplugged) parts on the 151. I started with the new On/off switch. Still read 26.01, no change. I then unplugged the headlight switch. No change. Then the highbeam switch. No change. BUT... after I disconnected the starter switch on the floor, I got a -3.02 reading with no sparks when I reconnected the batteries! Is the starter switch the issue? Or did it jut narrow it down a little? In an unrelated note. I got the brake lights to work with a new A1 switch and my A1 to A2 adapter.
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Re: New front harness, flat batteries

Postby Fil Bonica » July 12th, 2018, 4:29 pm

If you can , replace the starter switch with a new or known good one.
They are known to carbon up and creAre carbon tracks.

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