Two #40 wires?

w30bob · Post by **w30bob** » Tue Jun 06, 2017 7:43 am

HI Guys,

I picked up an NOS M170 harness to use as a pattern for a harness for my A1. I've been looking it over, as well as the wiring diagrams in the Pubs, to familiarize myself with it......but don't really see much difference between the two harnesses.

The only things I see that are different are the 170 harness has a wire #39 for the reel light, is a bit longer to the rear lights and it has two #40 wires. Am I missing any other differences?

Does anyone know why there are two #40 wires? The #40 wire powers the illumination lamps in the instrument panel. Both lamps are wired to a single 2 to 1 shell so only one #40 wire is needed to power both lamps. But the 170 harness has two #40 wires, each with a single Douglas connector (neither has a double connector shell to match up with the connector for the panel lamps) at the same place in the harness, and they are both the same length, so they are used somewhere behind the dash panel I guess. None of the wiring diagrams I'very found for either vehicle show two #40 wires. Anybody know what's up?

Thanks,
Bob

4x4M38 · Post by **4x4M38** » Tue Jun 06, 2017 8:05 am

That's weird. Easy to fix. One fork in the road, and both
paths will work.

w30bob · Post by **w30bob** » Tue Jun 06, 2017 3:14 pm

Hi B,

Yeah, it is. Since both are stamped "40" on their aluminum tags they were both intended as power sources for instrument panel lights.......per the nomenclature. But I've yet to see an instrument panel that doesn't join the two panel lamps together to match up with a single #40 wire.

Well, I guess I could use the spare #40 to power up my cranking stereo.......if I don't mind listening to it only when the lights are on.

regards,
bob

4x4M38 · Post by **4x4M38** » Tue Jun 06, 2017 6:24 pm

Ok, I have a question.

Where is wire 40 split?

Does it come out of the light switch with two wires
or one wire out of the switch then split?

I'm wondering if it was a motor pool fix of some kind?

Post by **wesk** » Tue Jun 06, 2017 7:39 pm

Post by **wesk** » Tue Jun 06, 2017 7:41 pm

Bob,

Have traced or ohmed out the two 40's to determine if both are really #40?

4x4M38 · Post by **4x4M38** » Tue Jun 06, 2017 8:03 pm

No. I know what the schematics show. I want to know what Bob
has installed.

Post by **wesk** » Tue Jun 06, 2017 8:25 pm

I have asked him to trace or ohm them out to determine how they are assembled or if he even really has 2 #40's. I would not want to be the one to ask him to unwrap his NOS harness!

I see no reason for the new M170 harness to use two separate wires since the M170 uses the same 1 into 2 splitter short harness at the instrument cluster.

w30bob · Post by **w30bob** » Wed Jun 07, 2017 7:59 am

Hi Guys,

Sorry for the delayed response, but I got tied up soldering that A1 gas tank I picked up at Aberdeen.....I'll tell you how that went in a different post. So back to this harness.........I've got no problem unwrapping it, as it has to be unwrapped anyway. But first I did ohm it out.....both #40 wires show continuity to each other and to pin B on the light switch connector....so they are both powered from the same pin.

Then I unwrapped it and you can see in the pic what I found. Obviously not ideal for having both wires carry a full electrical load....both wires should be run all the way to pin B for that. So don't know if this was "as produced" or a field fix. If you can't tell from the pic the first wire had its insulation stripped, then the second wire was wrapped around the conductor and soldered. I don't know what a "factory" splice is supposed to look like, so I'm anxious to hear what y'all have to say about this.

If it means anything this harness wasn't made with prestolite wire, it was made with wire marked:

CAVICEL S.P.A. Italy
1989 M-13486/1-5
1x14 AWG OZ

Thanks again for all the help,
bob

w30bob · Post by **w30bob** » Wed Jun 07, 2017 9:16 am

Hi Guys,

Just to complicate things a bit...........I checked the pic of the harness the seller had on Ebay, where I got this harness. The pic is of a different harness, not mine, but it also has two #40 wires, each with a single Douglas connector on it. So it's probably safe to assume all the NOS M170 harnesses he has are made this way. Go figure.

thanks,
bob

Post by **wesk** » Wed Jun 07, 2017 10:19 am

CAVICEL S.P.A. Italy
1989 M-13486/1-5
1x14 AWG OZ

Now that clears it all up. That harness is a NATO produced harness not US built. Obviously somewhere in Europe is a discussion or paper on why they did not like the 2 into 1 harness we used at the instrument cluster and went with two separate leads one for each lamp.

If your Harness had the FSN or NSN on it then my guess is the XXXX-OO-XXX-XXXX was not a -00- or a -01- which is the numbers used with US produced NSN's.

4x4M38 · Post by **4x4M38** » Wed Jun 07, 2017 12:18 pm

Hi Bob,
I wouldn't worry about load on one 14 gauge wire to one dash light.
If you'll remember the wire 40 is one wire from pin B to the double
Douglas connector at the gauge panel on the original harness.

Take care,

4x4M38 · Post by **4x4M38** » Wed Jun 07, 2017 1:21 pm

Are we absolutely sure the M170 used
that double Douglas connector to split
wire 40 to the dash lights?

The schematics I'm looking at show a black
box at the split on the M170 versus the
rectangle with the x in it denoting a connector
on the A1 schematic. I thought the black box showed a factory wire splice.

The M170 dash lights had a connector on the
back of each light versus the hard wired pigtail
with Douglas connector of the A1 dash lights.
An additional double Douglas connector would be
just extra cost and maintenance.

Just posing a question.

w30bob · Post by **w30bob** » Wed Jun 07, 2017 2:25 pm

Wes.......thanks......I wasn't aware NATO changed parts like that.

Brian........thanks also. I wasn't concerned about using each wire to power an individual panel lamp.....I was suggesting someone might use one to power the 2 panel lamps and then use the second #40 for something else that might have a high power draw (like my rocking stereo amp). But I am curious to hear what Wes has to say about your last post......I do see the black box you mention on the diagram.

thanks,
bob

4x4M38 · Post by **4x4M38** » Wed Jun 07, 2017 3:33 pm

I was looking in the Ord 9 G758 for photos of the ground wires you were
asking about and saw the wiring diagram differences. The electrical parts list
also has A1 and M170 specific parts like the gauge clusters and panels,
dash lights and I don't see the splitter listed for the M170 or a separate
double Douglas connector for the M170.

Lots of different parts numbers but that's why I'm asking. Wes is certainly
the subject matter expert and I'm hoping he can clarify what I'm seeing.
I did not have a chance to compare main wiring harnesses.
If they have the same main harness number then the rest of the stuff
is just muddled parts list stuff like we'be seen before.

If there are separate main harnesses then we might have a difference besides
the reel light and stuff.