Will Water Cause 2010 Prius Curt T-Connector Wiring to Smoke and Blow Fuse?

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Question:

Hi, I installed the CURT 56147 Custom 4-Pin Trailer Wiring Harness for my Toyota Prius 2010 in 2020. I dont use my trailer often. When I hooked it up yesterday, I had no lights. I found that the vehicle side was the problem with a multimeter. There was some water in the bottom underneath the 12 V battery and the converter box had come off the back wall, maybe due to heat or moisture? I had it ziptied it to the tail lite cable so I dont think it was in contact with the water in the botttom, but maybe with water running down the back wall? I disconnected the harness from the tail lights to replace it when I noticed the fuse box with a blown fuse. I got new fuses and as soon as I put one in, smoke came from the converter box and it blew the fuse again. Nothing was connected except the power from the battery. How do I figure out the cause of the original failure? Was it a short in the trailer that damaged the converter box, or is this installation location a problem, given that water might collect there or run down? Could you please adivse before I order and install a new harness? Thanks.

asked by: Lianne V

0

Expert Reply:

Yeah, that's not good, Lianne.

You're definitely looking at a leak in the back somewhere and you'll want to get that fixed ASAP for multiple reasons, least of all the trailer wiring blowing fuses. The Curt T-Connector # C56147 doesn't have the absolute best converter box, but I haven't heard of smoke coming out of the box (it will usually just fail if something is wrong) so I'm thinking moisture got to the box.

Step one is to get that leak fixed. If you aren't able to locate it on your own, then you'll want to take it to a shop that you know will fix the issue. Once that's fixed then I recommend picking up the Tekonsha T-One # 118505 wiring instead and doing a completely clean installation of everything just to make sure all of the parts haven't been affected by the water. The Tekonsha line of wiring is the best in the business so you can be confident this will be more reliable.

I'd love to hear what's going on at the back of your Prius that's allowing leaks. I have an '09 Prius and now I'm thinking I need to periodically check the back to see if I have water build-up. In heavy rain I'll see a drop or two run down the inside of the windshield, but I've just chalked it up to crazy weather.

expert reply by: Jon G

0

Lianne V.

11/11/2025

Hi Jon, thanks for your great reply. The Curt converter box was right under a small leak via the tail light of my Prius 2010 (passenger side), which gets clogged with tree debris. I don't think Prius 2009 has this problem. Imo it's a design flaw. The tail light needs to be removed in order to remove the debris. And for the tail light removal, the rear bumper needs to be removed or you risk breaking the bottom clip of the tail light, which is a lot of work. I managed to get most of the debris out with a work-around (loosening tail light rather than complete removal). The compartment under the battery had dried out and also has drain holes, so the leak in the light is the biggest risk for any connections in the harness. I ordered the Tekonsha T-one harness you recommended and its converter box has a better design with well-insulated wiring coming out from only the bottom, not bottom and top where the Curt harness probably got water in. It also has longer wiring, so I could install it away from the tail light leak. I attached the converter box using the screw hole at the top (?) to the rear of the body with a self-drilling screw, so it cannot move around or fall down as it would with tape and/or velcro. My trailer lights worked right away, so I am happy.

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Will Water Cause 2010 Prius Curt T-Connector Wiring to Smoke and Blow Fuse?

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