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All these colored wires

PaulvS

PaulvS

Well Known Member
The Dynon harnesses for the EMS and EFIS have more wires and longer wires than needed for my installation. I'm wondering how people have dealt with the excess, e.g. cut off and discard, or tie up into loops and store somewhere up behind the panel? Neither of the popular books (Aeroelectric Connection, Aircraft Wiring Guide) or the Dynon manual seem to cover this, but there must be a "good" way to do it.
 

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PaulvS said:
The Dynon harnesses for the EMS and EFIS have more wires and longer wires than needed for my installation. I'm wondering how people have dealt with the excess, e.g. cut off and discard, or tie up into loops and store somewhere up behind the panel? Neither of the popular books (Aeroelectric Connection, Aircraft Wiring Guide) or the Dynon manual seem to cover this, but there must be a "good" way to do it.
Click to expand...

They are provided long because they serve more than just RV's. Run your wire and terminate with some slack/loop for future use. Don't need to curl up 4' if not needed.
 
Make sure you leave enough slack to easily remove the screens far enough out of the panel to disconnect the harness plugs. Other than that, trim them where you need them.
 
I trimmed wire length on my Dynon installation leaving appropriate slack and service loop. Something about making wire harnesses, they seem to get tighter as I add wires to the bundle, so mind the slack. I also un-pinned and removed wires that were not needed in my application. Of course save them, easy to add back later if something changes.
 
EMS

My EMS CHT/EGT cable was just the right length to reach the starboard side sensors. I clipped and fit one set at a time so the connections were staggered but all one bundle. No service loop on that side. Port were longer. Excess has a service loop. Plus there's enough inside so the hinged panel drops.
The 37-pin was a headache. I fought for a bit then switched gears. It's not cut. I terminated all wires on a 37-pin D-sub female. It ended up right at the top center of the engine mount. That allows easy disconnect and if I need to add a sensor, just add it to the male d-sub. Worked great and looks good.
 
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I removed the unneeded wires from the plug and saved them in case I need them later. It's easy to remove wires from a Dsub.

Dave
 
Thanks all for the ideas. I hadn't considered de-pinning some of the wires but that is "doable" after removing the heat shrink and they can always be re-inserted later on if needed. About 1/3 of the EMS wires are not required and one or two serial lines could be removed from the EFIS harness.

I'll shorten the other wires as required. The DSub connectors to the display are easy to access by reaching up under the panel and so the service loops won't need to be very long.

Larry; interested in your approach. Did you fit a 37-pin panel mount type connector to the face of the firewall for plugging in the wires to the engine? I'm hoping that the location of the EMS module and the routing for the CHT/EGT wires will be able to reach all the corners of the engine.
 
D-sub

PaulvS said:
Thanks all for the ideas. I hadn't considered de-pinning some of the wires but that is "doable" after removing the heat shrink and they can always be re-inserted later on if needed. About 1/3 of the EMS wires are not required and one or two serial lines could be removed from the EFIS harness.

I'll shorten the other wires as required. The DSub connectors to the display are easy to access by reaching up under the panel and so the service loops won't need to be very long.

Larry; interested in your approach. Did you fit a 37-pin panel mount type connector to the face of the firewall for plugging in the wires to the engine? I'm hoping that the location of the EMS module and the routing for the CHT/EGT wires will be able to reach all the corners of the engine.
Click to expand...

No, but that's a neat idea. Only problem is it's a point of failure in a fire if the D-sub melts. I just used 37-pin D-subs.
First plan was solder sleeves but I wanted the ability to disconnect for troubleshooting and maintenance.
Second idea was Faston terminals but 30 or so pairs gets to be a really big pile.
Third idea was terminal strips. I even made a nice hinged mount so it could be pulled to work on it. Problem was the two strips weighed in at 1/2 pound.

Something else. The shared wires. Two power wires were shared on mine.
 
PaulvS said:
I'll shorten the other wires as required. The DSub connectors to the display are easy to access by reaching up under the panel and so the service loops won't need to be very long.
Click to expand...

Even with the apparent ease of reaching the connectors up under the panel, do yourself a favor and keep a healthy service loop on the harness. Once all the systems are in place, the systems plumbing, engine controls and seats and interior are installed it might be more difficult to reach up from below, especially in the years to come when you aren't quite as limber as before. It couldn't hurt anything to have that generous service loop. And like a haircut, if you decide to shorten the wires later it is easy to do, but if you wish you had left more service loop it is kind of too late.
 
Service loop

Like everyone said, do yourself a favor and leave enough for a comfortable service loop.
One more thing I did:
I copied the color coded wire scheme for the rest of the airplane for most of the avionics type installations. I spent a little extra money to purchase colored tefzel wire. Black for all grounds, red for 12V etc
Now you'll have use for the cut offs.
 
Color codes

N427EF said:
Like everyone said, do yourself a favor and leave enough for a comfortable service loop.
One more thing I did:
I copied the color coded wire scheme for the rest of the airplane for most of the avionics type installations. I spent a little extra money to purchase colored tefzel wire. Black for all grounds, red for 12V etc
Now you'll have use for the cut offs.
Click to expand...

I also used red, black, white and shielded. Cables labeled both ends. The panel cables were fabricated by Advanced and have labels on the D-subs. I did buy a section of the stick harness bundle because the pilot side was too short. That kept the color code consistent both sides.
 
airguy said:
Make sure you leave enough slack to easily remove the screens far enough out of the panel to disconnect the harness plugs. Other than that, trim them where you need them.
Click to expand...

YES !!!!!!! My biggest pet peeve in my RV8 !! :mad::mad::mad:

When I wanted to remove the D-180 I had to get a screwdriver blindly from under the dash back to the connector because if I pulled out the D-180 it would come out where I could see 1/4" of space behind the box so no space to get even fingers in to remove any connector. Infuriating !

The moment after you cut any excess wires, count to 3 seconds and you'll then realize you needed a little more.
 
Dealing with slack

I guess the idea is to leave enough slack so that the instrument can be pulled out to access the connector, but not so much slack that the wire flops around enough to cause problems?

AC43.13 says no more than 1/2" sideward movement for a wire when lightly pressured, but that would imply getting behind the panel to tie up the service loop, so I'm not really clear on what best practice actually looks like.
 
PaulvS said:
Thanks all for the ideas. I hadn't considered de-pinning some of the wires but that is "doable" after removing the heat shrink and they can always be re-inserted later on if needed. About 1/3 of the EMS wires are not required and one or two serial lines could be removed from the EFIS harness.

I'll shorten the other wires as required. The DSub connectors to the display are easy to access by reaching up under the panel and so the service loops won't need to be very long.

Larry; interested in your approach. Did you fit a 37-pin panel mount type connector to the face of the firewall for plugging in the wires to the engine? I'm hoping that the location of the EMS module and the routing for the CHT/EGT wires will be able to reach all the corners of the engine.
Click to expand...

I thought I made adequate service loops on my rv-10 too. Unfortunately ten years later, I wish they were much longer. My recommendation is the make any thing mounted to the panel so it can be pulled out and worked on your lap. It make you life much easier.

You never know what you may do 5-10 years down the road. I just finished my third panel upgrade in ten years. Having adequate slack will make life easier.

Also, don’t use a connector on the firewall. Especially for the cht/egt wires, since that could impact the values displayed on the efis. There are many through the firewall penetration devices available to minimize fire and co issues. Run all the sensor wires through the firewall to the location your emus is mounted.
 
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