Molex or not

[mc607]

I’ve read on VAF that the Molex connectors are not a favourite of some builders. If the Molex connectors are assembled as designed, with proper tools and techniques, are connected properly, and function properly during testing with no issues, what happens to them over time to garner the bad reputation? Does the plastic degrade and become brittle, do the pins degrade and or corrode prematurely?
I’m always trying to make my build decisions, and more importantly, deviations from KAI on facts, not opinions. Pictures are always helpful. Thanks in advance,
Todd

 

[Bavafa]

I believe the bad reputation comes from getting them crimped and connected properly. In my experience this applies only to the micro molex the type that is used mainly for the trim servos.
I personally have not had any issues with those that were crimped and connected properly and the mini Molex has been much easier to crimp and the connection has been solid for me.

 

[Tommy123]

Get a proper Molex crimper, they are not expensive. Or you can go full on transport category and use Cannon plugs.

 

[N804RV]

Molex makes a lot of connectors. The ones I don't like are these:

I use either Dsub connectors, or Deutsch style IP67 rated connectors.

 

[RV6_flyer]

As others have said, workmanship issues of them not being assembled and used correctly. I used Amp / Molex style connectors on my RV-6 26-years ago when I built it. They are all still in use.

Last week, I helped the local EAA Chapter put on a week long S.T.E.M. event for young people. One afternoon the group got a tour of a Diamond Aircraft repair facility and got to see several DA-42 undergoing maintenance. One of the students asked what the aircraft would cost. The answer was $1.6 to $1.8 million dollars and that there was a one year backlog on orders. This aircraft had a two molex connectors just like the ones in the above post that I could see in the instrument panel wire harness.

I have been retired 10-years from a career in the Aerospace Industry and used all kinds of connectors over the years. Like all connectors, there are limitations and recommendations from the manufacturers that should be followed. These Amp/Molex connectors are on the low cost side and when used / assembled as recommended by the manufacturer, can do the job they were intended for a long time at a low price point and they are lightweight.

 

[Walt]

I love Molex as I've made a good living fixing this stuff

 

[BillL]

I love Molex as I've made a good living fixing this stuff

Walt, what are the top two issues you find? Corrosion and loss of electrical contact? And what connectors have you seen that fail the least.

My expectation after working alongside the EE guys would be poor strain relief, lack of sealing (corrosion) and unreliable contact developed from vibration.

 

[rocketman1988]

Molex

Having worked with numerous connectors, I tend to agree with thee previous posts. Molex are cheap, lack moisture prevention, lack strain relief, and can be a pita to unpin successfully.

I much prefer Deutsch connectors. They are a bit more expensive but they work great and are exceptionally easy to unpin, if you need to make changes.

There are no molex connectors in my -10…

 

[Walt]

My expectation after working alongside the EE guys would be poor strain relief, lack of sealing (corrosion) and unreliable contact developed from vibration.

All of the above, cheap bent pins compared to machined pins used in quality connectors. Acceptable for lights and other non-essential equipment, but likely to cause problems regardless of where they are used. Don’t have to have a EE degree to understand you get what you pay for. This is what I used to refer to as parts from ‘Radio Shack’ which was synonymous with cheap POS.

 

[n82rb]

Having worked with numerous connectors, I tend to agree with thee previous posts. Molex are cheap, lack moisture prevention, lack strain relief, and can be a pita to unpin successfully.

I much prefer Deutsch connectors. They are a bit more expensive but they work great and are exceptionally easy to unpin, if you need to make changes.

There are no molex connectors in my -10…

i have used thousands of molex connectors in my business. it comes down to using the proper connector, and using the proper tools.

molex pins have perfectly fine strain relief if the proper crimper is use, as stated, they are not cheap, but if the proper tool is used, they make a perfect crimp every time. the ones i use are about 400 dollars a piece. same for with pining and unpinning, use the proper tool and its fast and easy.

boeing and airbus use them by the thousands, but it comes down to application. you wont find a KK series connector connecting the fadec to the engine.

if you want to use a 5 dollar connector where a 30 cent connector will work fine, go for it, its your airplane and your pocket book. but, dont just think that more expensive is automatically better.

bob burns
RV - 4 N2RB

 

[rocketman1988]

i have used thousands of molex connectors in my business. it comes down to using the proper connector, and using the proper tools.

molex pins have perfectly fine strain relief if the proper crimper is use, as stated, they are not cheap, but if the proper tool is used, they make a perfect crimp every time. the ones i use are about 400 dollars a piece. same for with pining and unpinning, use the proper tool and its fast and easy.

boeing and airbus use them by the thousands, but it comes down to application. you wont find a KK series connector connecting the fadec to the engine.

if you want to use a 5 dollar connector where a 30 cent connector will work fine, go for it, its your airplane and your pocket book. but, dont just think that more expensive is automatically better.

bob burns
RV - 4 N2RB

Never implied that more expensive is necessarily better; stating a fact that the Deutsch connectors are a bit more expensive.

After working with and comparing molex and Deutsch, there is a clear winner for me, and that is what I chose.

It really Comes down to personal preference for our aircraft. Mine is Deutsch and I would stand those connectors up to any comparable Molex. In the end, no Molex for me…and yes, I have the proper crimper.

 

[Tommy123]

Whelen has used Molex connectors for decades.

 

[dmattmul]

Molex issues for me

I’ve read on VAF that the Molex connectors are not a favourite of some builders. If the Molex connectors are assembled as designed, with proper tools and techniques, are connected properly, and function properly during testing with no issues, what happens to them over time to garner the bad reputation? Does the plastic degrade and become brittle, do the pins degrade and or corrode prematurely?
I’m always trying to make my build decisions, and more importantly, deviations from KAI on facts, not opinions. Pictures are always helpful. Thanks in advance,
Todd

Like most of the challenges we face building or maintaining the devil is in the details. Will Molex connectors work well? Yes, yes, yes if used for connections that stay moisture free and dry and it helps if never disconnected and connected. They will work great. Probably 98% of the connections in the 14 fit this process condition. This one (see pic) does not, and I know more 14 builders who have had issues with this connection than not had issues. It gets exposed to at a minimum fairly high humidity conditions and possibly actual water but works well until you need to unplug it and then plug it back in (Like after paint) after it's seen humid conditions (at least for some length of time). I doubt the Molex engineers would give the ok for this application.

The wing root Molex connectors could also be a possible source as their environmental conditions are also subject to high humidity and possible water intrusion. (The 14 does not have a wing fairing molding) and water could enter the wing root fairly easy. Since they do not get unplugged and plugged back in fairly often (if ever) most likely they will work. The Deutsch connectors are top notch and anything FWF highly recommended along with locations that have high humidity and need to be plugged in and out.

Micro-Molex have additional issues besides the above.

 

[wirejock]

Molex

I worked quite a few years in radio service.
Every Motorola radio back then had a Molex. Some had been in service too many years for me to count. Like 10+. Sitting on a sun baked dash board. Spewed with coffee, soda, etc. I never saw a Molex failure.
Every failure was the microphone cord because operators would wind it around to eliminate the slack. I ran many a radio rabbit hunt back then. Radio heat sink would be hot enough to fry eggs right next to the Molex. I would snip the mic cord and leave it to see how long before it was reported. Then I would tell the operator, 500 others including the Main Office heard every word while the repeater was locked up.

 

[andoman]

SDS CPI2 connections at the gold box are all molex.
But I have used Deutsch or single d-sub with heat shrink everywhere that I had a choice because of my predilection to put pins in the wrong receptacle...

 

[wirejock]

Molex

I should have mentioned. The only Molex I used were on lights because the wires are too big for D-sub pins. I used .060 pin 6-pin Molex.They are the only connections at the wing root. All the other cables are full run to the panel. D-sub were used on wires 20 AWG or smaller.

 

[blaplante]

The MOLEX pictured above... my experience is they take a lot of force to connect and disconnect. Up in some difficult spot then when it finally comes apart my hands crash into other wiring... not good. And takes two hands to pull apart.

I like connectors with a spring latch. Squeeze and it disconnects easily.

 

[bbaggerman]

As others have mentioned there is nothing intrinsically wrong with Molex connectors. I like them and I use them often. The question is are they the right connector for your application. IMHO most of the time for aircraft use they are not. I mainly see two types of problems.

First, I have seen a number of failures because of improper crimps. Everyone knows about under crimping. That is pretty easy to test for by giving the wire a good pull. But over crimping is a problem also. Too much crimp and the wire is crushed and broken. I have had to replace several on my RV-12 that were over crimped and broke off. A higher quality connector system has a certified crimp tool system, and doesn't rely on how hard the guy using the tool can squeeze.

Second is environmental concerns. The cheap Molex system offers no protection from the elements and doesn't have pins that are corrosion resistant. Attached are a couple of photos of the Molex connectors as I found them leading to the landing light in my wing. Note the burn mark on one of the pins from overheating caused by a corroded pin.

I think a higher quality connector system is warranted, especially in locations that are only minimally protected from the elements. There are some really nice automotive connectors that are light, inexpensive, and offer excellent protection from the elements.

 

[mc607]

Thank you all for contributing to this thread. Lots of valuable information, as always.

 

[rv6ejguy]

Not smart to use unsealed connectors in places that can get wet.

Used inside dry areas, crimped properly, Molex stuff works for decades. We've built many thousands of harnesses over 29 years using them.