vf171

I have an '02 K2500 Suburban and a problem anytime I hook a trailer to it. Last winter I was hauling my tractor home from my mom's place, where I just cleaned her driveway, and I started to slide. The trailer was borrowed and did have trailer brakes but I didn't have a controller to operate the brakes. Anyway, I was on the brakes the whole way down a long hill and I noticed all the dash lights, including the radio, dimming everytime I hit the brakes. I thought it was something messed up with the trailer wiring.

Fast forward to today. I recenlty picked up a nice little 4x6 utility trailer and was hauling some stuff to my MIL's place and I noticed the same thing happening again. This time though I was going through an adapter since my 'burban has a 7 pin connector and the trailer has a 4 pin connector.

I noticed when I put the brakes on the lights on the dash would dim the same as before but when I would turn my turn signal on the lights on the dash would blink in unison with the turn signals.

I just repainted the trailer last week and checked all the wiring. At first no lights worked so I started checking the ground when I remembered the fuses. 3 of the fuses for the trailer lights were blown. I replaced them. After that everything was good but I noticed the front passenger side marker/turn signal bulb was blown. I replaced it and all the lights worked. I used my 4-way flasher to test the lights and the turn signal lever to double check each side individually. Everything checked out okay. It was dark out when I tested so I pushed the brake pedal and checked for the brake lights to light up to be sure they working too. They were. I don't recall looking at the dash while I was doing this since I was focused on the lights on the trailer so the dash lights may have been dimming when I did this but I didn't see it.

So has anyone encountered anything like this before? I checked the fuses when I got home this afternoon and they are all good. Lights on the trailer are all working as far as I can tell. I'm seriously confused.

I'm leaving for PA Monday morning on a bussiness trip but I'm taking my Suburban and the little trailer to pick up some turf tires for my Kubota I won on Ebay. I'm a little nervous about it. I know PA troopers are pretty tough on trailers. I don't want to risk loosing lights and not knowing it then end up with a ticket while travelling with my boss.

Any help is appreciated.

350Suburban

I'm going to school for a diesel technology degree and am currently studying diesel electricals. What this sounds like is a short to voltage. What happens is a wire rubs through at the same time another one does, typically in a loom and they can pass current through each other. It seems like your interior lights have shorted to your brake lights so that when you make the connection to flow current to your brakes on the trailer, the power to your interior goes there too. If you have a multimeter you can diagnose this easy.Pull the fuse for the interior lights, then probe your brake light socketon the trailer as someone presses the pedal. Take note of the voltage. Then, reinstall the fuse and probe the socket again, if it has a higher voltage, you have a short to voltage. Good luck!

zipperman19

That may be the problem, but it might be more simple than that. Have you ever noticed that when you try to roll up your windows all at once with the interior light on, they dim a little. For instance if your windows are shut at night and you have the interior dome lights on, you can pull up all four of the window close switches and the lights dim a little inside/ on the dash. I think you are experience the same problem with your trailer. Your trucks electrical system needs to light up additional brake lights on the back of the trailor which are taking electric from the rest of your truck.

You should look into this situation further if you feel its a short like 350Suburban said. I would start by checking for corrosion at the trailor connector. You may have some corrosion/rust which is causing too much resistance in the wires or causing a minor short. However, I think this situation is unlikely.