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Wire Splicing Methods

rockitdoc

Well Known Member
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What's the consensus? for connecting the electrical bits FWF, ie, fuel flow, oil pressure, fuel pressure to the boxes in the cabin? Molex or similar for multiple wires in one connector (like three for the fluid pressure sensors) or spades for individual wires? Or, something else?
 
Think modular assembly.

What's the consensus? for connecting the electrical bits FWF, ie, fuel flow, oil pressure, fuel pressure to the boxes in the cabin? Molex or similar for multiple wires in one connector (like three for the fluid pressure sensors) or spades for individual wires? Or, something else?

I did everything without connectors, but was always considering Deutz DT connectors. They are weather sealed, extremely reliable and easy to assemble. I really don't like the molex or weather-pack after using them. Lots of places to get DT, and means another DMA crimper. They have larger pins available to carry a higher load than the d-sub as needed.

In retrospect, I would recommend that one minimize the variety of connector brands for the whole project. I was cheap and considered all the connectors overkill and unreliable, but think I was wrong now having to deal with splicing after the fact with upgrades and changes. There will always be changes, IMO.

Just a thought . . . .
 
What is the best connector system?

I am at the point of getting serious with wiring and I would like to use a unified connector system for my 8A project. Bill’s suggestion (above) looks good. Any others I should consider? Thanks!
 
Why spice anything FWF?

I use spade terminals to connect the EGT and CHT probes to the EMS leads - because they may need to be replaced somewhere along the way. Those get covered with heat shrink after mating.

Things like oil temp/pressure and fuel pressure get a ring terminal at the sender, the other end of the wire goes to the EMS in the cabin. Starter solenoid are ring connectors as well.

At least for the SkyView system the wire harness that comes with the EMS has leads long enough to not need spicing.

The pMags wires go from the pMag connector to inside the cabin.

Carl
 
Just me

I would never use a Molex on an aircraft. Period.

The best are the Mil Std 38999 series, but those are a little overkill for us.

I recommend and I used the Deutsch series. They are readily available from Digikey or Mouser. The are just as good as the Mil STD. They are widely used in industry. But they require a proper crimper. Other benefits are that they are easy to service, provide good strain relief to prevent wire breakage, and are weather proof. For firewall forward, best to use the gold plated contacts.
 
Why spice anything FWF?

I use spade terminals to connect the EGT and CHT probes to the EMS leads - because they may need to be replaced somewhere along the way. Those get covered with heat shrink after mating.

Things like oil temp/pressure and fuel pressure get a ring terminal at the sender, the other end of the wire goes to the EMS in the cabin. Starter solenoid are ring connectors as well.

At least for the SkyView system the wire harness that comes with the EMS has leads long enough to not need spicing.

The pMags wires go from the pMag connector to inside the cabin.

Carl

I followed a similar philosophy. In a couple of cases, where I wanted easy disconnect for testing like the hall sensors for EI, I used weather pack connectors. The Deutsch sound nice, but I am too cheap to buy a crimper for 100's of dollars for installing a few of them. The basic molex type crimper works for the weather packs. Items with pigtails, like the red cube, I soldered and left a 6" loop. When I replace, just cut and solder new one in. Have had too many failures with crimped butt terminals, but that could be from not buying the expensive ones.
 
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Why spice anything FWF?

I use spade terminals to connect the EGT and CHT probes to the EMS leads - because they may need to be replaced somewhere along the way. Those get covered with heat shrink after mating.

Things like oil temp/pressure and fuel pressure get a ring terminal at the sender, the other end of the wire goes to the EMS in the cabin. Starter solenoid are ring connectors as well.

At least for the SkyView system the wire harness that comes with the EMS has leads long enough to not need spicing.

The pMags wires go from the pMag connector to inside the cabin.

Carl

Fluid pressure wires 16AWG go to EMS but are not long enuf as supplied (16”). EMS harness has 22AWG that are long enough (6’) to go from subpanel to fluid pressure wires FWF. But, they need to be connected together somehow. Splicing was probably wrong term. What type connector to go from 22ga on EMS and 16ga on fluid sensors? Same issue for fuel flow. EGT and CHT came with spades.
Why not Molex? Too large?
 
D-sub

I am using D-sub on low amp connections like signals but only if they have to be spliced. 9 pin or 15 pin. I prefer a solid run with no splice. My lights are .063 Molex.
 
Fluid pressure wires 16AWG go to EMS but are not long enuf as supplied (16”). EMS harness has 22AWG that are long enough (6’) to go from subpanel to fluid pressure wires FWF. But, they need to be connected together somehow. Splicing was probably wrong term. What type connector to go from 22ga on EMS and 16ga on fluid sensors? Same issue for fuel flow. EGT and CHT came with spades.
Why not Molex? Too large?

I just did these connections on my -10 and used knife splice terminals like below with heat shrink over them.
A blue one on the larger wire and a red one on the smaller wire.
 

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I just did these connections on my -10 and used knife splice terminals like below with heat shrink over them.
A blue one on the larger wire and a red one on the smaller wire.

Seconded. Regular PVC electrical tape from 3M works just fine to insulate these FWF instead of heat shrink, and is much easier to remove ten years later.
 
Tape FWF

Seconded. Regular PVC electrical tape from 3M works just fine to insulate these FWF instead of heat shrink, and is much easier to remove ten years later.

I used heat shrink FWF and in many other connections for several reasons. It keeps the connections together with some compression from being shrunk....shrank?....:p It stays put. Places I had PVC electrical tape started to come unraveled due to temperatures and time. The stickum on even the 3M tape seems to have a half-life that causes it to come undone. And heat shrink just seems to look better and we all know what looks can mean......IMHO
 
Molex connectors are clunky, cheap, unreliable, wires rattle inside them and they are not designed for the type of environmental conditions seen in aircraft systems. They get yellowish and brittle over time and are a PITA to de-pin even with plunger extractors. Anybody who has been around them over time cringes when they see them.

Here is another vote for Deutsch DT (larger wire) and DTM (smaller wires). They are weatherproof with silicon seals and snap together and remove very easily while having complete positive lock when connected. They are a pleasure to deal with. I always use the closed barrel type contacts, never the open crimp style. There are less expensive crimpers available in kits on major web sites. Most regular DSub crimpers will work as long as the position is set. Here is one example:

https://www.amazon.com/ABN-Deutsch-Closed-Barrel-Crimper-Ratcheting/dp/B01N3P2S17

Deutsch also do not require and special tools for insertion or extraction. Push the contacts in to set. A small blade screwdriver will release the contacts for easy extraction.

For the specific question of using 22 gauge wire for one connector and 16 gauge wire on the opposite connector Deutsch makes pins with barrel ID for different gauges of wire. For that combination I would use the larger DT connector and instead of getting special sized pins for the 22 gauge I would simply strip the smaller wire 2 to 3 times longer than the required depth and merely fold over the exposed wire to make it thicker inside the connector barrel. Strain relief is provided by silicon rubber seals so that is not an issue.
 
Butt splices

Your basic crimp type butt splices work very well. There are some special connectors for EGT & CHT. Vendors usually provide them with their engine gauges.

Butt splices are simple, secure and easy to replace. Just leave yourself a bit of a service loop. Cover them with heat shrink if you like but it’s probably not necessary.
 
I’ve used a few Deutsch DTM connectors (like for the trim in the tail where I thought water could get in) - they use DTM size 20 pins which are good for 7.5 amps. You can crimp them with the same crimper as Dsub pins.

For higher pin counts or higher amps I have used CPC connectors.

I was very confused about all the connector options and proper pins etc so made a reference document. Link below if it’s helpful to anyone and I would be grateful to any criticism if I’ve made any errors etc.

https://drive.google.com/file/d/1cw7OPO0I_RDc_H0VNA7YjZ_BSVK-W-RA/view?usp=drivesdk
 
For the CAN Buss, use #24 and put in one pin. Set crimper for #20.
 

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I’ve used a few Deutsch DTM connectors (like for the trim in the tail where I thought water could get in) - they use DTM size 20 pins which are good for 7.5 amps for each contact position. You can crimp them with the same crimper as Dsub pins.

For higher pin counts or higher amps I have used CPC connectors.

The Deutsch DTM are the minature versions (that's what the "M" at the end of DTM stands for). The DTMs use size 20 contacts good for 7.5 amps usable with 16 to 22 gauge wires. DTMs are great for avionics and signal wires and low amp power circuits. DTMs come in 2, 3, 4, 6, 8 and 12 position connectors.

For step up in amp capacity you can get the Deutsch DT connectors (no "M" on the end). DTs use size 16 contacts accommodating 14 to 20 gauge wire and are rated at 13 amps continuous for each contact position. DTs come in 2, 3, 4, 6, 8 and 12 position connectors.

For higher amperage capacity yet Deutsch has DTP connectors ("P" standing for power in reference to the higher power capacity). DTPs use contact size 12 and are rated at 25 amps continuous for each contact position. DTPs can accomodate 10 to 14 gauge wires. DTPs are only available in 2 and 4 cavity connectors.

Finally Deutsch also makes what they call Jiffy Splices which come in 13, 25 and 100 amp sizes. The contacts are 16, 12 or 4 sized. These are single butt connectors consisting of one pair of male and female contacts with a protective boot. Jiffy Splices can easily be disconnected and reconnecfed in the field.
 
EGT / CHT gremlins that were traced to bad splicing has made me a believer in the EI WIRE OVERLAP CONNECTOR / SPLICE OLC-2 for that particular application.

10-05470.jpg
 
EGT / CHT gremlins that were traced to bad splicing has made me a believer in the EI WIRE OVERLAP CONNECTOR / SPLICE OLC-2 for that particular application.

10-05470.jpg

Yep. Yep. These nylon barrel overlap connectors with set screws are my favorite too for EGT/CHT probes and any other signal splices under the cowl. EI developed these after years of complaints about the original spade connectors. Most electronic engine instrumentation problems can be narrowed down to bad or intermittent connections. These EI overlap connectors will eliminate a lot of that as long as installed per instructions. EI puts them in all their modern engine monitor kits and will sell a package of just connectors to anybody who wants to retrofit whatever brand of existing probes they have.
 
Dave and Jim,

I think I am sold on the Deutch connectors. Would either of these be a good connector kit to start?

https://theelectricaldepot.com/deutsch-connectors-accessories/deutsch-connector-kit

Also, I have the Stein barrel pin crimper. Would that work, or is it worth it to get the Deutch crimper?

Thanks!

Steve. I don't have a Stein barrel crimper so my answer is perhaps. I bought a third party Deutsch compatible closed barrel connector tool from Amazon. I also bought a used Astro rotating barrel tools (positioners built in on a rotisserie). I started to use that too so I could keep my nice Daniels crimpers for avionic pins only. Both of those have adjustable crimp setting based on connector size. Online auction sites with have new and used Deutsch crimpers and a quick perusal just now showed many in the $40 range.
 
I think I am sold on the Deutsch connectors. Would either of these be a good connector kit to start?
Ordering a DTM kit might not be a bad idea. Each connector needs maie and female shells and pins plus the wedges and silicone plugs that secure and seal the pins once they're inserted in the shells. You'll get all those with the kit. I ordered piecemeal and wound up short a part or two on a few occasions.

Also, I have the Stein barrel pin crimper. Would that work, or is it worth it to get the Deutch crimper?
It's been a few years since I bought the crimper, but I'm reasonably sure that this is the one I purchased for larger (>20 ga) DT connector pins -

https://theelectricaldepot.com/deutsch-tooling/deutsch-crimp-tools/paladin-pa1461-4-indentsub-crimper-20-12-awg-by-greenlee-p-1033

You'll find it cheaper on Amazon -

https://www.amazon.com/Paladin-PA1461-Pro-Grip-Crimper-4-Indent/dp/B0848FPFCW

For smaller (20-22 ga) DTM pins, I used my Daniels crimper with a dSub turret but you can find a cheaper tool at SteinAir -

https://www.steinair.com/product/4-way-indent-crimper/

Hope this helps -

Dave
 
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Terminal Block

Since the Dynon EMS sensors need a common 5V, I put a terminal block next to the Van's sensor manifold. Kept all the 5V and Ground connections together, and made connecting the sensor wires from the Dynon bundle simpler.
 

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interesting...reading this thread I keep going back to terminal blocks in my mind
but I never have cared for those crimped connections for the eye rings (or any other connections)
I keep remembering the din rail mounted terminal blocks used in the industrial power feed and control cabinets I used to work on for work. Some of those terminal were pretty slick the way they were designed...super easy to get a great connection, super easy to troubleshoot and modify down the road. Bound to be some of them able to stand up to the dynamic rigors needed for some of these connections I would think??
 
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