the 5 wire is for the big trucks with extra gauges like brake air pressure or tranny temps and etc.
It is very handy when you switch your amp meter for the later volt meter since when using a transistorized regulator or the 60 amp one wire GI alternator wires # 8 & 9 no longer have any juice on them. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
I don't think the US contract M38A1 came with the 5 wire at all. The M170 5 wire doesn't show up in any supply manuals until the 1966 edition of the TM 9-2320-208-20P. In that manual they have two separate figures. Fig 32 is the M38A1 with the 4 wire harness and Fig 33 specifies the M170 with the 5 wire harness. I believe only the Canadian contract M38A1 CDN 2 & 3's came with the 5 wire and the transistor regulator. Maybe the Canadian owners can provide some insight here. Possibly the 64 or later USMC contracts may have also. I think the early M170's were 4 wire until at least 1961/62. Even so the Army often subbed the transistor regulators into the A1's and most likely that dictated the use of the volt meter and the 5 wire harness in the field. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
my 1956 ord 9 - page 155 states 2 harness, instrument cluster assy, one for the M38A1 and another for the M170. Two different part numbers. It mentions 4 connections for the M38A1 but states nothing for the M170.
Page 154 states the battery and generator gauge for the M170 fitting the two gauge clusters used by the M170 only.
page 121 shows the 5 wire spider also again with a different part # then the M38A1 shown on page 119. 7526600 4 wire and 7526601 - 5 wire for M170
my april 1955 TM9-8014 for m38A1 and M170, page 219 clearly shows the 5 wire spider for the m170.
The m170 needs the 5 wire spider due to the batter/generator gauge used instead of the voltage gauge. To my knowledge all m170's had the battery/generator gauge thus needing the 5 wire spider.
My m170 is a 1954 and it has the 5 wire spider.
I do not know about the M38A1 ever having the battery/generator gauge installed but if it did it would need the 5 wire spider.
No doubt most 170's were 5 wire. The 8014 was introduced in 55 and it also shows the M170 using the M151 dash lights and hi beam lite. I think we are all aware that when the voltmeter is used the 5 wire harness should also be used.
My point is the M38A1 did not come from Willys with a 5 wire harness nor volt meter. The first mention of using a voltmeter in the M38A1 comes in the 1959 TM 9-2320-208-20P where it says issue until stock is depleted on the amp meter then use the voltmeter. So for A1's up thru 60 the amp meter was the original gauge. The -20P's represent parts stocked and issued in the field and do not often represent original factory parts. Also in the last M38A1/M170 parts manual issued TM 9-2320-208-20P dated 1966 it still illustrates the M38A1 cluster Fig 32 on pg 47 with the 4 wire harness and the M170 fig 33 on pg 48 with the 5 wire harness. Unfortunately neither fig offers the harness part #.
Note the 4 wire harness.
Bottom line here would be only truly reliable source of data for the first few M170's would be factory production prints and BOPs. Same with any transition of the A1 to a factory volt meter during the 60's. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
My point in all this is to point out that the 5 wire spider wasn't just found in "big" trucks. Obviously the M170 used it and also the m37. Maybe even the m175 also but thats another story. Just giving the original poster some facts about the 5 wire spider and its appplications.
And I am addressing the mentioned use on the M38A1.
I am careful to not say always, every, none and never I'll find the files soon I hope on two early M170's that are set up with amp meter and wires 8 & 9. Two members sent me photos of their's some time back and I hope I can find them and the notes. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Aug 31, 2010 Posts: 1739 Location: SO IDAHO
Posted: Sun Apr 26, 2015 1:41 pm Post subject:
Would it be safe to say the 5 wire harness modified to 4 wire would be an
approved motor pool substitution should the stock 4 wire not be in the supply line? _________________ keep 'em rollin'
RICKG MC 51986 DOD 01-52, '50 CJ3a
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