Posted: Thu Jul 16, 2020 6:51 pm Post subject: Technique to mating Douglas connectors
I feel that I'm missing something obvious, but I've got gouged up fingers tonight from trying and completely failing to mate Douglas connectors.
Is there some tip or technique to make these easier to mate up? Or conversely, 'how NOT to make them mate up'. I've only managed to get 4 of the ones on the gauges on the dash connected. I tried using a little silicone spray on the rubber boot in case the problem is just too much friction on the rubber, but it doesn't seem to have made much difference.
In addition to the wiring harness and gauges that I have, I also have a handful of 'loose parts' of Douglas connectors and without the pins or wires they go together somewhat as I would expect - somewhat difficult, tight, but possible to get together with moderate force. So that's with just shell, ring, rubber boot, female to female coupler, boot, ring and finally shell. _________________ Tundra (really my name, not my truck)
When I did mine, after I used all my good ones, I noticed that if the center plastic piece (called "connector" in the diagram, you called it "coupler") is a shade too long it can cause the problem you describe. I carefully trimmed the plastic or phenolic equally from both ends until the two shells would successfully mate. I used sandpaper on a wood block to knock them down a bit. It didn't take much.
I also noticed after taking them apart some time later, that the rubber boot pieces can get deformed even cut if not carefully centered in the bushings, which also seems to interfere with them going together smoothly. As you said, some lubricant seems to help.
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
Last edited by RonD2 on Thu Jul 16, 2020 8:35 pm; edited 3 times in total
Any idea if there is a defined 'correct' length or is it a matter of "50s manufacturing variability"? Was "trim to fit" normal expectation back when Douglas connectors were contemporary? _________________ Tundra (really my name, not my truck)
Joined: Oct 02, 2014 Posts: 2059 Location: South Carolina, Dorchester County
Posted: Thu Jul 16, 2020 8:12 pm Post subject:
I didn't look very hard for a defined spec length and never found one. I suspect sloppy manufacturing. And I don't know if I have 1950's parts or modern re-pop's. All I could recommend if you have at least one that works --- measure it against one that doesn't.
I could take one of mine apart and measure it for you?
I doubt that a mechanic back in the day would bother trimming a 5-cent piece? Tossed it in the trash and got another. _________________ 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
Last edited by RonD2 on Thu Jul 16, 2020 8:23 pm; edited 1 time in total
The reproduction Douglass connectors are crap. I hope that isn't what you are using.
I built all my Douglas harnesses and I learned the following trick to aid in mating:
Disconnect the connection. Pull the shells up the wires to get them out of the way. Next, get the little metal bushings off of the rubber and up by the shells, out of the way.
Then lube the rubbers with some light oil or similar. Push them back off of the terminal up the wire. Lube the contact. Then slide the rubber back over the contact. it is IMPORTANT that the rubber doesn't get pushed on so far as to let it come around and close down past the larger diameter or the contact. In other words, correctly installed the face of the rubber is flush with the step in the contact.
Connect the two contacts to the adaptor or whatever you call it and make sure the terminals seat all the way in WITHOUT pushing the rubber further onto the contacts. Then slide the little metal bushings down and seat them on the back of the rubber parts. Finally bring the main shells together and they should mate up just fine!
Hope that all made sense. _________________ '52 Dodge M37, '42 GPW, '48 FrankenJeep CJ2A/M38, '50 CJV-35(U), '51 M38, '42 WC-57 Command Car, '44 WC-51 Weapons , (2) M1941 Sperry 60" Anti-Aircraft Searchlights, John Deere M-gator, '44 White M3A1 Scout Car
I had the same problem with repro connectors. My old ones were an easy fit, new ones wouldn’t go. A touch each end on the belt sander did the trick... _________________ Gary
M38 - June 1952
I would suggest that you not use petroleum based liquid oils on the rubber parts. Stick with a dry teflon based spray lube or use what pro's use with tightly sealed electrical connectors, Connector Grease. A clear electrical connector d electro-insulation lube.
The reproduction Douglass connectors are crap. I hope that isn't what you are using.
I built all my Douglas harnesses and I learned the following trick to aid in mating:
Disconnect the connection. Pull the shells up the wires to get them out of the way. Next, get the little metal bushings off of the rubber and up by the shells, out of the way.
Then lube the rubbers with some light oil or similar. Push them back off of the terminal up the wire. Lube the contact. Then slide the rubber back over the contact. it is IMPORTANT that the rubber doesn't get pushed on so far as to let it come around and close down past the larger diameter or the contact. In other words, correctly installed the face of the rubber is flush with the step in the contact.
Connect the two contacts to the adaptor or whatever you call it and make sure the terminals seat all the way in WITHOUT pushing the rubber further onto the contacts. Then slide the little metal bushings down and seat them on the back of the rubber parts. Finally bring the main shells together and they should mate up just fine!
Hope that all made sense.
I don't know the provenance of the connectors I have - I've got two types, some black ones (picked up from online vendor last year) and some brown ones (came with my wiring loom from deBella). I'm assuming from what's mentioned here that trimming/sanding the beveled plastic portion a bit is ok, but not to get to the point of touching the actual conductor in the center of the connector.
The lube I tried is Liquid Wrench Silicone Spray. I didn't spray it directly on the rubber boot, I sprayed it on my gloved finger and then smeared from there on the rubber - my concern was getting trying not to get it on the actual pin. Looking at the link Wes provided, it looks like they are talking about applying a dielectric directly on the pin, which seems odd to me - is the assumption that the contacts will wipe the grease away at the actual contact point but otherwise provide a barrier to corrosion everywhere else?
Thanks to all for the pointers, I'll give it another try! _________________ Tundra (really my name, not my truck)
Joined: May 30, 2014 Posts: 3482 Location: Texas Hill Country
Posted: Fri Jul 17, 2020 7:16 am Post subject:
One other thing to keep in mind. That rubber bushing is an integral part of the waterproofing of the connection. Whether you ford or not, there has to be a little crush to the rubber for it to seal properly.
Try to use new bushings. Old ones in many cases are dry and crunchy, in various levels. They will not compress.
Some of what you are experiencing may be due to the rubber bushings not compressing. It doesn’t take much, a little on both ends. In my case it was just a minuscule amount to connecting up, but they just wouldn’t go. New rubber bushings fixed it in most cases and they are cheap.
Btw, I’ve found Midwest Military as good or better pricing on all the Douglas pieces than anyone. Don’t be afraid of looking at the obvious vendors just to save a buck. Their quality is usually better, and in many cases the prices are just as good as you shopping for bargains.
Joined: Oct 02, 2014 Posts: 2059 Location: South Carolina, Dorchester County
Posted: Fri Jul 17, 2020 7:47 am Post subject:
You shouldn't have to trim-sand the connector-coupler down to the metal contacts in order to get the shells to mate easily. If you have to take it down that far there's probably something else wrong.
I use No-Ox grease on the metal to metal contacts of electrical connectors. It's not a dielectric grease.
When I did mine I had a combination of the connectors for inside the douglas shells. Some were from the harness it had initially, some from Vintage Wiring and some from Mullins. There seemed to be two types of connectors, black ones that seem to be a modern plastic and brownish maroon ones that seemed to be more like bakolite. The brownish maroon ones seemed to fit well and it required only a moderate amount of force to close the shells. The black ones were impossible to use without filing the ends down some. I measured both types and the black, seemingly more modern, connectors were about 1/16 of an inch longer than the older ones and the overhang on the ends between the edge of the plastic and the metal connector inside were longer or deeper. Once I adjusted the ends a little with a file the black ones seemed to work well, I just made sure I filed them incrementally so the shells were not loose fitting. _________________ R G Mutchler
M274A5
M-38 MC13312
http://willysmjeeps.com/v2/modules.php?set_albumName=rgmutchler&op=modload&name=gallery&file=index&include=view_album.php
Joined: Apr 14, 2005 Posts: 285 Location: Livermore Ca.
Posted: Fri Jul 17, 2020 11:00 am Post subject:
I pretty much us same as mdainsd...buy use wd40 _________________ '51 M38 #22936,
'51 M100 Dunbar
#01164782
'53 M100 Dunbar
M416b1
2- M762
MVPA #11788
MVCC LIFER
Joined: Jul 10, 2018 Posts: 97 Location: Western Washington
Posted: Tue Jul 21, 2020 7:59 am Post subject:
I recently rewired the entire M38. It was a pain literally. The new production connectors are just a wee bit to long. My procedure was:
-Grind down each end of the connector a small amount
-Pull back the rubber bushing
-Apply some dielectric grease
-Insert metal tips completely into the connector on each side
-Slide up rubber bushing to connector
-Connect metal shells if possible. If not, cuss profusely and grind a bit more off connector and reattempt. _________________ Rick Eades
1951 M38 & 1967 M715
Then lube the rubbers with some light oil or similar. Push them back off of the terminal up the wire. Lube the contact. Then slide the rubber back over the contact. it is IMPORTANT that the rubber doesn't get pushed on so far as to let it come around and close down past the larger diameter or the contact. In other words, correctly installed the face of the rubber is flush with the step in the contact.
The top one of these is as the harness was delivered, the bottom one is my attempt at matching what you are talking about here with being flush with the step in the contact. Is this what you mean or do you mean something different?
_________________ Tundra (really my name, not my truck)
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