2009 Jetta TDI trailer wiring

How does one wire up a trailer light harness for a 2009 Jetta? The wiring is really weird, each bulb operates like a dual filiment bulb but in actuallity its a single filament bulb. They use pulse width modulation to vary bulb brightness and to save wiring, brilliant but at the same time god help you when you need to diagnose bulb problems. So how does one wire up to this system? Can i just splice in and will the computer doing the pwm automatically compensate?

Reply to
Fred
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IIRC, there is an adapter you can get to do these. Be very, very careful about splicing into the existing harness, the computer is not designed to drive the trailer directly.

Reply to
PeterD

Further to this, putting even the lightest of trailers on a Jetta - almost any VW or similarly sized *small* car - is just not a good idea.

Peter Wieck Melrose Park, PA

Reply to
pfjw

Codswallop! I towed a tent trailer for thousands of miles through Canada and the US, through mountains and freeways with a bone stock 1990 Mazda MX-5 Miata, with no problems at all! Also put many miles towing trailers with a 1971 Datsun 810 s/w.

There are dire warnings about improper connections to the Jetta wiring, and we were assured that only the dealer is the place to have it installed.

Stuart H.

Reply to
Stuart H.

That is as it may be. But the brute fact of the matter is that a light vehicle hasn't the mass to handle even a small emergency with a trailer - entirely apart from transmission loading, suspension loading and so forth. That you are lucky to-date does not make what you choose to do a good idea.

Peter Wieck Melrose Park, PA

Reply to
pfjw

So I have yet to hear anyone explain the physics of this. an 80,000 pound rig is pulled by a 20,000 pound tractor? Purely designed to tow so there is one difference. Or a 6,000 Dodge has a combo weight of

18,000. Again designed to tow. Now my 2,800 pound Toyota was rated to pull 5,000 pounds. So I do not get why I could not tow a 1,000 pounds behind my Jetta. Car is rated to tow that load. Any rig used to tow has a big difference in acceleration and braking. When was the last time you saw an 80,000# rig on the race track. Now look again and you will see 10 wheel tractors on the race track.

I am a huge fan of brakes on trailers which is where many people screw up. Trailer brakes should have enough power to stop the trailer and then some. My equipment trailer was much easier to use with two axles of brakes then it was when it had just one set of brakes.

I have seen overloaded trailers wagging the tail of a pickup truck on the interstate. Been there and done that at relatively slow speed. Note to self. Calculate load of trailer and check tire pressure before towing.

Reply to
Jim Behning

That is as it may be. But the brute fact of the matter is that a light vehicle hasn't the mass to handle even a small emergency with a trailer - entirely apart from transmission loading, suspension loading and so forth. That you are lucky to-date does not make what you choose to do a good idea.

Peter Wieck Melrose Park, PA

uhhh...my 03 Jetta TDI wagon is rated to tow about 1,000 pounds, and tongue weight of 165 ISTR. However, it seems the exact same vehicle is rated for nearly 1,000 kg--about 2000 pounds-- in Germany. Recently talked to a Smart owner who had a very small trailer--mobile blacksmith--hooked to his diesel Smart. In Canada, the 40 hp diesels had no stated towing capacity, but in Germany the official government road safety figures were about 750 pounds. Seems that in North America, fear of litigation is the deciding factor, not safety per se. Towing a reasonable sized (to the tow vehicle) trailer is not a problem...if you always take it into account and adjust your driving speed, distances, and habits accordingly. A modest aluminum tent trailer weighs about 1,500 pounds, which is still a lot less than the mass of even a small car. However, if you tow a fibreglass house trailer (Boler 13ft, 760 pounds, aerodynamic) like I do, then no problems.at all, even in emergency stops and accident avoidance. If a car can handle four adults and their luggage in the normal course, then it can handle one adult, a dog, and a light trailer. Just don't try to tow a 20+ footer weighing 3,500 pounds with your Golf.

Jim Bartley PEI

Reply to
George Mills

Please note the interpolations:

On Apr 7, 11:07=A0pm, Jim Behning

That, and the tractor has - at those weights - 10 tires on the ground, a driver trained and licensed to operate it (consider a multi-engine commercially licensed pilot *Qualified" on and handling a 777 vs. a civilian pilot in a single-engine Cessna 140) and yet for all that they still screw up with spectacular results on-occasion.

There is a significant difference between *can* and *should*. You can jump off a high bridge into a river or onto concrete. Perhaps you

*should* not.

Brakes are helpful for stopping in a straight line. They are not terribly *helpful* if you are stopping otherwise, especially if your vehicle has anti-lock brakes and you trailer does not - and, BTW, most combinations extend the anti-lock system to the trailer brakes as well these days. If the trailer has strong brakes which grab on a slippery curve, you will tend to straighten out rather than follow that curve. That could be acutely embarrasing under certain conditions. Kinda being caught between whiplash and tighteing the bow...

AMEN to that. Worse than towing at all - overloading. Then you are betting everything against the house rather than merely playing close odds. The problem with physics is that it really does not care about nameplates and ratings very much, but about the immediate conditions when its various laws and forces come into play. Comparing a VW jetta TDI at a curb weight of ~3,000 pounds to a Freightliner Cascadia with a curb weight of ~20,500 pounds has you agreeing only on the fuel used. As if a 3,000 pound general-purpose passenger vehicle is rated to pull 12,000 pounds of trailer - based on the same 4:1 ratio.

Sorry - driving is dangerous enough without taking everything to the margins.

Peter Wieck Melrose Park, PA

Reply to
pfjw

Small quibble here: Four adults and their luggage (and possibly their dog) distributed about the center-of-gravity. Not a trailer added as an appendage hanging off the back with all the tongue weight on the back.

Peter Wieck Melrose Park, PA

Reply to
pfjw

wrote in message news: snipped-for-privacy@g37g2000yqn.googlegroups.com... On Apr 8, 7:24 am, "George Mills" wrote:

Small quibble here: Four adults and their luggage (and possibly their dog) distributed about the center-of-gravity. Not a trailer added as an appendage hanging off the back with all the tongue weight on the back.

Peter Wieck Melrose Park, PA

I'll quibble back. You raise an extremely good point. There are many misguided people out there who don't know or won't pay attention to limitations. I specified a Boler fibreglass trailer at 760 TOTAL pounds, and NOT 760 on the tongue, more like 100 or so. Remember all trailers MUST have some positive tongue weight! They are also aerodynamic, nor generally affected by cross winds, and have real car sized tires, on a big steel frame so they have a balanced and very low centre of gravity. I suggest that people Google Boler to find out about these remarkable trailers and their history. I have towed it very successfully and safely with an ancient automatic Corolla with 300,000+ km, with about 2/3 of its nominal 108 hp left. No appreciable fading on the drum brakes either, even in hilly (4-15% grades) country.Within reason, a(n) (aluminum) folding tent trailer is similar, but I never considered one because they tend to have smaller, skinnier tires, more weight, and poorer areodynamics than a Boler or similar type of trailer like a Casita or Trillium, and so tend to bounce around a bit more. I also specified NOT some freakishly large and long trailer that exceeds the length and weight of the towing vehicle. The second scenario will waggle the tow vehicle, even if it could pull it, and unbraked it would be a downhill disaster waiting to happen. Cross winds would make it so easy to jackknife as well. The first is quite safe, as long as you account for it being behind you. They were designed to be safely towed by small economy cars.

Jim Bartley Prince Edward Island

Reply to
George Mills

As with me. I was towing a CombiCamp with my 1990 Miata. Trailer GVW loaded was 900lbs, tongue weight was approximately 30 lbs. Never a problem. One trip alone was over 5,000 kms through Alberta, Saskatchewan, Manitoba, North Dakota, South Dakota, Wyoming, Montana, Idaho, Washington, British Columbia, and home to Alberta. That included

2 crossings of the Rockies. Know your vehicle, its capabilities, and the towed unit.

My 2006 Mark V Jetta TDI 5M sedan is rated at 907 kg (2000 lb) maximum trailer weight, and 91kg (200 lb) maximum tongue weight, per my owner's manual. Obviously there would be no problem towing a Boler of the size Jim has!

Stuart H. Alberta

Reply to
Stuart H.

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