Trailer Wiring Problem

<div class='quotetop'>QUOTE(brighamwj @ Oct 26 2007, 06:47 PM) [snapback]530970[/snapback]</div>

Ah... bummer! I can't help but think that if the module were at fault that it would blow the fuses even with no load on it. But apparetly you can drive around fine without the trailer lights. That definitely makes me suspect *something* from the trailer. And since you've checked everything for shorts, and found just one problem in the burned bulb, I'd be even MORE suspect that the burned bulb unit is your problem.

If the failed bulb welded itself short, I suppose that could cause your problem. The module doesn't do much magic. Just combines the turn and brake signals since trailers typically only have one light for both signals - unlike most modern cars. Any problem you have at the trailer is just passed directly to the fuse box in the car. The first thing I'd try is lopping off the failed light, and try again. Definitely worth a couple of bucks (for the fuse) to determine if that's the problem.

First thing I did with my new trailer is to swap out all the incandescents with LED so there wouldn't be much extra load on the electrical system. I'm not sure what all is involved in this sealed unit you speak of - but if it failed this early, it can't be of very high quality!

Good luck. Let us know how it goes.

 

For new LED lights, the best advice I can give you is to just Google LED Trailer lights.

Look through and find what you need. I replaced all of the lights on my tailer, and had to custom-fit them (none were exact replacements). What came on this expensive trailer were about the cheapest, ugliest incandescent lights you can buy.

 

Does your Draw-Tite "module" have a separate 12volt connection to the battery? (Darell's EV site didn't show any indication of that.)

If your module is not isolated (no separate 12v power), the trailer lights are powered by the Prius lighting circuits. Since incandescent bulbs draw a LOT of power, you likely overloaded the Prius harness. Fortunately the fuses blowing should have protected anything from damage.

Draw-Tite sells an "isolated" module (the ModuLite). This module connects to your vehicles light harness to sense voltages, but it does not draw any current from the lighting harness. The trailer lights are powered directly from the battery. This fully protects the car from any shorts or overloads.

For my Camry Hybrid I used the Modulite. My 2nd time out towing one of my trailer lights stopped working. I checked voltages and the module wasn't putting out power. Hmm...

I found that trailer plug harness had gotten crushed by the trunk latch and some wires were shorted.

But the Camry lights still worked and I didn't blow any fuses - The isolation works!

To reset the Modulite, pull its fuse and then replace it. When it loses power the units resets.

 

You can wire the modulite easily. Simply cut the wires to the "module" that you already have. Cut them close to the module so you have plenty of wire to work with.

The Modulite uses the same color wires. L turn (yellow), R turn (green), brake (red), tail (brown) and ground (white?). The generic Modulite kit is fine. You already have the adapters to the Prius wiring harness installed.

The Modulite needs a 12 volt supply. I wired mine directly to the battery.


Again, you may not actually have a short in the trailer. If I remember correctly, a brake bulb can draw over 5 amps (one bulb). This alone could be blowing the fuses. The Modulte will safely draw this power directly from the battery.


Get those Kayaks wet! I have a small (17') Sailboat. Unfortunately Winter is approaching quickly here in Chicagoland.

 

I took a different approach to the trailer wiring. I actually use this with my avalon, but could have just as easily used it with my prius. or any other car. I use this for the occasional times that I pull a small trailer to the place at the lake with a riding lawn mower as the cargo. I did not want to tap into the car's system at all.

The first thing that I did was to isolate all the lights on the trailer above "ground". They get their ground through one of the four pins in the trailer connector anyway. Then I built the somewhat low tech setup shown in the pictures below from things that I had on hand. The only thing that I bought was the tool box. The yellow box at the end of the red cable goes up by the driver. The toggle switch turns on the tail and running lights. The two push button switches are the left and right brake/turn lights. Push them both and the brake lights are on. Push either one of them intermentely and the turn light flashes on the side relative to the switch you are pushing. The 12 volt battery in the center happens to be the same one that I carry in the prius for a jump start if it is ever needed.

With a little more work, one could add a flasher to make the turn lights work automatically. The heavier current is handled by the three relays on the right side of the box. This setup is also very useful when working on the trailer lights. You don't have to have the trailer connected to the car and you can take the control box with you to the area in which you are working. When not is use, the control box and cables store inside of the tool box.

Just another way to get the job done.

 

<div class='quotetop'>QUOTE(brighamwj @ Nov 12 2007, 10:45 PM) [snapback]538694[/snapback]</div>

The battery is only 12 amp hour rated, so it wouldn't last very long with night time driving using incandescent bulbs, but it might do well with LEDs. I only plan on using it during the day and the trip is only about an hour each way.

I hated to drill holes in the Pelican box, but I had it and it fit the need.

 

<div class='quotetop'>QUOTE(brighamwj @ Nov 11 2007, 08:50 PM) [snapback]538167[/snapback]</div>

I'd suggest going with the Modulite no matter what. It will protect your electrical system.

I bought the #118176 Modulite. This one is "universal". As I described in my previous post the Modulite will wire into the wires from your existing "Camry" kit. Cut off that old module and wire in the Modulite.

For the 12volt supply, I bought an inline fuse holder from Radio Shack. I think I used a 10 amp fuse. No problems with running the battery down. If they designed the Modulite well, it should have very little parasitic current draw.

 

Hello all

I'm having a bit of a different problem and wondering whether anyone has ideas.

I used the same Draw-Tite 18308 wiring setup (Thanks, Darell and Nate!). So far, I haven't plugged any trailer wiring into it. However, since installing it, I'm getting occasional electrical problems with the Prius. The Brake and ABS warning lights come on at times, then go away when the car is restarted. And, a couple of times, it has been hard to get the car started. It will respond to the Start button with various lights but not "Ready". After 6 or so restarts/reboots, it eventually works. I've now removed the wiring to see if this goes away, but not sure yet.

Has anyone seen similar behavior? Is it likely related to the wiring? Would changing to the Modulite make a difference? Doesn't seem so, since there is no load on this wiring yet.

 

It is my belief that changing over to a Modulite or even purchasing LEDs will not fix the problem. I support both recomendations but only because I value the of LEDs and circuit isolation.

I believe the problem is in the harness with a remote chance it is
in the bulb receiver. If the problem is in the harness then LEDs and Modulite will not fix the problem (Actually the Modulite will fix the
car fuse problem, but will cause the Modulite fuse to fail thus displacing the problem, not fixing it). So Here is my thinking:

If I summarize your observations correctly, you are saying that when you drove over a bump, you discovered that a car fuse was
blown when you finally arrived at home.

I interpret this problem to be an intermittent short revealed through the bumps. If you were driving during the day when you encountered that bump, that suggests the short is in either the turn signal circuit or in the stop signal circuit. If you were driving at night you would also have to include the running light circuit.

Finding an intermittent short is not easy. I would trace the intermitent short with the following proceedure. Begin by looking at the trailer. Do the wires run in conduit or do they run, exposed, through occasional eyelets?

If they do NOT run through conduit, I would first check the wires for
exposure (bare) as they run through the eyelets.

In addition, you might remove all bulbs from the trailer, connect the drawtite to the trailer harness and run car and trailer over bumpy
roads. try running with just the left blinker on........then after about
10 bumps, try running with just the right blinker on......if after each test you still have not blown a fuse.......go over the bumps hitting the brake at the same time. check the fuse after each run. Finally try running lights in the same manner.

If the above does not blow a fuse, then the odds are that one of the bulb receivers is not functioning correctly. Insert only one bulb and run the tests. remove and insert a different bulb and run the tests. repeat until all bulbs have been tried (separately). between each bulb changout, check the fuse.

l hope this helps. Please let me know how your experiments ended or what you may have done that enabled you to diagnose the problem successfully.

Bil