Cobra Trailer Wiring Presentation Available for Download

[OHM Ω http://aviation.derosaweb.net]

I finally purchased a glider that came with a Cobra trailer last year (remember the old adage?).

The trailer came with a cobbled together vehicle connection and the original incandescent lighting. So I set about "correcting" this. I really can't help myself to not try to "improve" everything electrical that I come across.

This presentation covers;

* Euro 7-pin connectors
* US 4-Flat and 7-pin connectors
* Wiring a Cobra trailer to use a US 4-Flat
* Converting 4-flat shared turn/brake into separate turn and brake
* LED conversion
* Miscellaneous information

http://aviation.derosaweb.net/presentations/documents/Trailer_Wiring_Made_Easy.pdf

Let me know if you find this useful, wrong, and/or downright dangerous. Also, what trailer electrical changes have you made?

Thanks, John OHM Ω

[Michael Opitz]

At 16:32 23 August 2017,
T0hNIOKEpiBodHRwOi8vYXZpYXRpb24uZGVyb3Nhd2ViLm5ldA ==
wrote:
>I finally purchased a glider that came with a Cobra trailer last year
>(reme=
>mber the old adage?). =20
>
>The trailer came with a cobbled together vehicle connection and
the
>origina=
>l incandescent lighting. So I set about "correcting" this. I really
>can't=
> help myself to not try to "improve" everything electrical that I
come
>acro=
>ss.=20
>
>This presentation covers; =20
>
>* Euro 7-pin connectors
>* US 4-Flat and 7-pin connectors
>* Wiring a Cobra trailer to use a US 4-Flat
>* Converting 4-flat shared turn/brake into separate turn and brake
>* LED conversion
>* Miscellaneous information
>
>http://aviation.derosaweb.net/presentations/documents/Trailer_Wi
ring_Made_E=
>asy.pdf
>
>Let me know if you find this useful, wrong, and/or downright
dangerous.
>Al=
>so, what trailer electrical changes have you made?
>
>Thanks, John OHM =E2=84=A6
>
Nice to have all of the info in one neat package.
Thanks, John...
RO

[[email protected]]

Agreed -- Thanks very much for putting all this information
in one place....

AE

[Dave Nadler]

Thanks John!

What does that 2-wire to 3-wire converter do when you've
got the brakes plus a turn signal on?

Are you going to sell kits ?? ;-)

[[email protected]]

Dave,
Here's a video of my installation: https://youtu.be/MIxLi-8Deic
This one is a slow motion clip to show the amber LEDs brief flicker when the brakes are applied: https://youtu.be/8VDm_nGM_-Q

I started by replacing my incandescent lights with a pair of large round red LED taillights. Then heard about the 4 to 5 wire adapter here on RAS, so bought that and a pair of smaller round amber LEDs to come up with this setup.

All that's missing is a center brake light, but these are bright enough that I should be safe safe.

5Z

On Wednesday, August 23, 2017 at 3:17:04 PM UTC-7, Dave Nadler wrote:
> What does that 2-wire to 3-wire converter do when you've
> got the brakes plus a turn signal on?

[bumper[_4_]]

When I swapped out all the lights for LED on my Cobra in 'O5, I added a tailfin mounted LED brake light. I used a 12 volt relay for the "logic", driving the relay coil with one brake light and the relay NO contact with the other. Both brake lights on at the same time, fin light on also.

There's another inadvertent mode also. If you have a turn signal and brake lights on at the same time, the fin light flashes with the turn signal :c(

I have the aluminum top and had to mount the fin LED with wedge to bring the LED beam angle down enough to be effective for following cars. My center marker lights flash with turn signals, don't remember if it came that way - I may have changed that too.

[OHM Ω http://aviation.derosaweb.net]

On Thursday, August 24, 2017 at 12:40:21 AM UTC-5, bumper wrote:
> When I swapped out all the lights for LED on my Cobra in 'O5, I added a tailfin mounted LED brake light. I used a 12 volt relay for the "logic", driving the relay coil with one brake light and the relay NO contact with the other. Both brake lights on at the same time, fin light on also.
>
> There's another inadvertent mode also. If you have a turn signal and brake lights on at the same time, the fin light flashes with the turn signal :c(
>
> I have the aluminum top and had to mount the fin LED with wedge to bring the LED beam angle down enough to be effective for following cars. My center marker lights flash with turn signals, don't remember if it came that way - I may have changed that too.

Bumper - Having a flashing HEP light might not be a big deal, maybe flashing is even better. I cover this in my file. But if you replace the 12V relay with two diodes you can get ride of this flashing "problem" and is more reliable. Again, see my file.

[OHM Ω http://aviation.derosaweb.net]

On Wednesday, August 23, 2017 at 5:17:04 PM UTC-5, Dave Nadler wrote:
> Thanks John!
>
> What does that 2-wire to 3-wire converter do when you've
> got the brakes plus a turn signal on?
>
> Are you going to sell kits ?? ;-)

Dave - It works just like in your car. The upper amber lights work as turn signals and, independently, the middle red lights work as brake lights. I don't know what is going on inside the Curt module but I hear clicking so relays (and diodes?) must be involved.

The only "problem" I have seen with this adapter is that when using emergency flashers both the red brake lights flash with a "hyper-flash" of the amber turn signal lights. Not a big deal. This may be caused by the Curt module or from using LED versus incandescent. Again, not a big deal.

But, no, I am not planning on selling kits. I haven't found a cheap US source for the 7-pin Euro connector! Anyone know of one?

- John OHM Ω

[OHM Ω http://aviation.derosaweb.net]

HEP = "High Eye Point". Any modern vehicle has one these days. I didn't add a wedge thinking that with 21 LEDs in the light I am using it should be bright enough.

- John OHM Ω

[[email protected]]

John- For 7 pin Euro connectors, try:

https://www.etrailer.com/s.aspx?qry=7+pin+european+connector

Thanks for the instructions. Helpful, like your other presentations.

[Charlie M. (UH & 002 owner/pilot)]

Usually they are called "CHMSL" or "center high mounted stop light" instead of HEP. I guess either can work.

As to hyperflash, it's a byproduct of the low resistance in an LED used in a signal. Typical fix is either a high watt low ohm resistor. Similar happens when you lose a blinker filament, the circuit load drops.
You can find info on the DiodeDynamics install page. DD makes various LED lights.

I have thought about a series of eight LEDs across the top of the dog house.
Four red in the middle connected to brake circuit.
Two amber or yellow on each end tied into the turn signals.
Makes cars further back see what you're doing.

[Charlie M. (UH & 002 owner/pilot)]

OK, read through your document, good info and nicely done.

Crimp connectors, squeeze some dielectric grease inside the connector before inserting the wire, helps make the connection last.
All electrical connections, use dielectric grease, whether in a screw type terminal block, spade connectors, etc.

You can go to a lot of auto parts stores and get a small tube of dielectric grease, Permatex "67V" (.33oz/9.5g) should be easy to find and cheap.
I have also used white lithium lube, wheel bearing grease and Vasoline (human body type petroleum jelly) instead of dielectric grease.

I see your document has what I referred to, combo stop and turn light, cool..

If running new wire, my feeling is there is no such thing as "too big". Big wire may be difficult to connect or bend/run. Use 14-16ga wire, less voltage drop, easy to run.
ONLY use stranded wire. Copper work hardens, so any flex or vibration will make the wire brittle and break. Use stranded wire vs. solid wire. I have seen people use bell wire or thermostat wire which is solid but maybe they had a lot. Most stranded wire is 7 strands for small size, 16 or more for larger sizes.
Tin coated wire resisted corrosion better but costs a little more.

And no, I'm not picking on the info provided, it covers most things. Just trying to add even more info to a good document.

[JS[_5_]]

Nice work, John!
It's also easy to wire the car to International standard, even those with LED lights.
Buy the trailer wiring kit for your vehicle, buy another similar module.
Run vehicle power to both modules.
Cut the wire from the brake light connector in the wiring kit for your vehicle, run it through the brake light circuit in the second module.
(use crimps)
Optionally add reverse and Aux wiring for a floodlight on the trailer fin box and interior lights.
Jim

[Dave Nadler]

On Thursday, August 24, 2017 at 11:52:21 AM UTC-4, Charlie M. (UH & 002 owner/pilot) wrote:
> Crimp connectors, squeeze some dielectric grease inside the connector
> before inserting the wire, helps make the connection last.

Absolutely DO NOT PUT GREASE ON WIRE PRIOR CRIMPING.
Wire and connector need to be perfectly clean, and
you need to use the CORRECT crimping die and the CORRECT
wire size for the crimp connector.


> All electrical connections, use dielectric grease, whether in a screw
> type terminal block, spade connectors, etc.

Dielectric grease is good for sealing for example rubber boots around
connectors. Keep it away from the terminals.
Another big no-no is putting dielectric grease onto spark plug nuts!

> I have also used white lithium lube, wheel bearing grease and Vasoline
> (human body type petroleum jelly) instead of dielectric grease.

Do NOT use other greases, and only use dielectric grease as it
is intended to be used. I know this is RAS, but Really!

[OHM Ω http://aviation.derosaweb.net]

On Thursday, August 24, 2017 at 10:24:56 AM UTC-5, Charlie M. (UH & 002 owner/pilot) wrote:
> Usually they are called "CHMSL" or "center high mounted stop light" instead of HEP. I guess either can work.
>
> As to hyperflash, it's a byproduct of the low resistance in an LED used in a signal. Typical fix is either a high watt low ohm resistor. Similar happens when you lose a blinker filament, the circuit load drops.
> You can find info on the DiodeDynamics install page. DD makes various LED lights.
>
> I have thought about a series of eight LEDs across the top of the dog house.
> Four red in the middle connected to brake circuit.
> Two amber or yellow on each end tied into the turn signals.
> Makes cars further back see what you're doing.

"center high mounted stop light" - Well, that's a mouth full! ;-)

About the hyperflashing. I have read about the resistor trick to fool the car into thinking that the trailer still has incandescent bulbs. Seems counterproductive as one of the points of LED is lowering the current needed to light them, resistors defeat that. I think that this is less of an issue with 2014 and beyond vehicles which are rapidly converting to LEDs too. Also, it seems strange that the brake lights are fine while the turn signals hyperflash. I put this down to the Curt converter (separates the two signals), not due to the vehicle (works the same in my 2004 and 2014 vehicles). Anyway, not much of a concern. Things flash. Good enough for me.

- John OHM Ω

[OHM Ω http://aviation.derosaweb.net]

A new version of this presentation was just uploaded with some corrections and additions. More changes may be forthcoming so I suggest that you don't download a copy but just refer back to my site when you need the latest info. Plus there are other presentations at the same place that you might find useful.

http://aviation.derosaweb.net/presentations

Enjoy.

- John OHM Ω