Best 1974 BMW 3 Series Trailer Wirings

Installed on a 2009 328i BMW, took more work to get interior panels off/on in trunk area than the wiring. I had the electrical wiring diagrams for the car which really helped.

This product works as expected. There is not too much to the installation, just plug it in properly and mount the ground wire. I did not find an easy way to mount this to my wife's Odyssey, or to the trailer hitch (item# 75270). Luckily, I do prototype design and manufacturing. So I came up with my own solution. I designed and made my own bracket to mount the 7 pole to the trailer hitch. It works like a charm, and looks great!

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i had to replace these two items as my dear daughter went down our goat path driveway too fast. they replaced the originals from etrailer from the prior year. shipping is timely and customer service actually helps! i wired from battery to controller to hitch myself, and everything fit.

Great build quality, but unfortunately it will not work to legally use a 4-pin trailer being towed by a 7-pin Euro/Land Rover plug. Its simply mapping 4 of the 7 pins to the following pins on the 4-pin side. Left running, Right running, Stop and negative, there is no provision for indicators or dual sided brake lights. It needs diodes (which it does not have) to do this. etrailer just needs to update the description as this is a good basis to make various adapters.

Received product in good order, well packaged, initial some delay, manufacturer was chased by etrailer, and earlier dispatched by manufacturer; delivery trail clear stated, very good. On receiving verified at UHAUL: connect with 1983 Land Rover (Defender) 110 Stationwagon (photo: rear, while on transport): all functioned ok. Apparently some diode(s) included, as the 7 pin has individual stop light which translates as left AND right indicator on flat pin. Emergency flashing (all indicators left and right) tested ok at UHAUL (connecting to trailer). LR has European homologated 3.5 metric Ton (7700 lbs) tow hook and has done some 60,000+ miles towing with current odometer reading 578,000+ km (on/about 360k miles)

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Replaced the wiring and lights on my 1992 boat trailer. I was able to get everything needed from etrailer. I think Optronics is of the highest quality and recommend both etrailer and Optronics product.

Works very well after re-wiring trailer lights with waterproof distribution box.

Wiring worked perfect for my project. I replaced the wiring on my 14 foot utility trailer. If I was to do it again I would buy the next length up. I would have liked to have a little extra wiring if I was to ever need it.

Your sales staff is second to none. Keep up the good work. You shipped minutes after I placed my order! Very impressed! Marty

I wanted one with a LED tester built into it to "trick" my SUV into thinking I had a trailer connected when really it was just a bike rack so the car didn't slam in it's brakes while reversing thinking it was something else. So I bought a different adapter. The picture slightly deceived me into thinking this had LED tester because the plug is attached by a rubber string (that I thought was a wire). So add another picture of the other side and that would eliminate my confusion. 4 stars because it probably works the way 99% of people would want to use it for.

Everything worked out well. On time and fits perfect. Attach hitch setup and my new Ridgeline. It comes with a 2" inch receiver and I have a full compliment of 1.25. stuff from my previous car. All from etrailer i must admit! so I needed the 2-1.25 reducer, a good lock, and the 7-4 reducer for my goodies! Thanks for the grest service

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Only gave 4 stars because it was a bit confusing. I have a lot of auto wiring experience; from car stereos,amplifiers and all manner of accessories. All of the info on etrailer indicated that the color coding didn't match up. So I went into it disregarding the standard color coding, when in fact it was just as it should be.

Good thick rubber and plug works perfectly.

Not too difficult to install, but I would recommend using a car lift so you don't have to work from your back (review includes wiring harness and Brake Controller)

Perfect . My new Subaru hitch has a flat plate to which the dealership attaché the 4-flat. I used “2 L-brackets” to accommodate the 90 degree bend of the adapter bracket.

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Works fine. Reasonable price. I'm happy that etrailer is around.

Thanks for the follow up!

Great product no issues at all. Product as described & fit properly.

Pretty straight forward. I used it to switch my European trailer's connection to be able to connect to my Wrangler's 4-pin trailer hookup. No issues. works great.

Çable good but after putting new 7way plug on truck cable wire colors did not match etrailers picture

7 pin connector separated from cable. I was expecting that "Molded Cable" meant that the connector was fused to the cable insulation but instead, the two separated almost immediately after I installed it. It still works fine as the wires are connected securely inside the connector but with the outer covering pulled out like this, I don't think it will last very long.

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Works great and etrailer folks did an outstanding job with quick turnaround and communication…thank you!

Exactly what we had been looking for. Now I can hook up multiple trailers with different connectors and all the electrics on each trailer works. I mounted mine directly to the receiver hitch frame. The biggest challenge for us was routing the backup wire from the taillight housing, through the body of the truck to the connector. the rest went together fairly easily. Seems to be pretty solid and looks much better than the loose pigtail connector it replaced.

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GREAT ACCURATE REPLACEMENT WIRING.

Timely shipment. I’ve bought from your company before and haven’t been disappointed. Nice job.

So, I converted my brand new Loadrite trailer to LED'S and wanted to add up a reverse light. I purchased this 5 wires trailer light harness to do the trick. Very good quality and the color code stayed the same. Had no problem what so ever and was an easy swap. I soldered every wires and protect them with heat shrink tubing and that should last a very long time. Thank you.

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Very bad experience. Placed an order on 5-24-23 for an item that showed to be in stock on the website. Receive an email stating that is back ordered and due to ship 6-5-23, several emails later still no wiring harness. Finally 7-10-23 I receive an empty envelope, well not completely empty it has a letter from USPS stating that the enclosed was found loose in the mail. A box would have been more appropriate to ship this item, as I have been in shipping for two different companies for 38 years now. I am unable to upload pictures of the envelope, I will send them via email.

I used this harness to rewire a 10ft vintage RV. There was plenty of length to reach the rear lights. I used Scotch Locks to tap into the wiring for the side running lights. Very good product.

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Very happy with every aspect of my order. Received product and quality appears to be outstanding. I’m especially impressed at the instructions made available to install the wiring harness, written with the product and link for video. All bases covered and follow up to make sure all goes well. Am confident of their assistance should I need it.

Very strong wire on the connector. Finger hole access is priceless!

Good quality and fast shipment. The hole makes it easy to disconnect without straining the cables.

We are a U-Haul Dealer and bought this for use as a test device only. We need to test many vehicles trailer connections to be sure there are no issues before renting a trailer. Some vehicles have the trailer lighting connection mounted in a way that makes it impossible to see the lights on the testers. Of all the testers that are on the market, NOBODY makes one with the test LED's on BOTH sides of the unit. With the test LED's on the end of this unit you can always see them, regardless of the position the trailer socket is mounted! We have the same problem with the 4 pin testers. We purchased 2 different brands where one tester has the LED's on the top, the other has them on the bottom.

Your website led me to believe that this product could tell me whether the electric brake control on the tow vehicle works, without actually connecting the tow vehicle to a trailer. That is not the case, so I spent $20 on something I don't need.

Sooo, bought another one to match my truck side connection as GM uses Pollak, which are known to not play well with other brands. The design is just a wire clamp to wire it, which I did with the first one, but trying to get it secured I stripped out the screw. There are no torque specs provided. I’ll move to crimped ring terminals on this one and dial back the torque a bit.

Routine trailer maintenance. Absolutely nothing worse than fighting trailer lighting or electric brake issues when traveling.

Perfect! extra long so I got rid of all my bull crab wiring

Well made, especially the mounding around the plug. Pin alignment was very good.

The pins were too big by a little bit. Had to force the female plug into the socket

I purchased both pieces and got the fifth that I was looking for for my motorcycle. I would recommend this for anyone wanting to wire the motorcycle to pull a trailer.

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