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I had a U-haul trailer hitch installed on a 2006 Volvo S-60. As soon as you plug in the trailer, the brake lights go out, both on the car and the trailer. You have to unplug the trailer, turn off the car, and then re-start the car to get the brake lights to work again. Plug the trailer in again, and out go the brake lights. Tail lights and turn indicators work fine. Checked and tested the trailer thoroughly and it seems fine. What could it be?
They are running the lights directly off the power feed for the car's bulbs. The bulb power feed is via transistors and it shuts down the feed with excess load.
You can get a trailer light module at most RV sellers that have shops (Camping World) that supplies power to lights from the battery and the taps into light circuits only signals the module to switch on the power. This takes the load off the bulb circuit.
A lot of vehicles have transistor circuits like that and must use the trailer light module.
go look here:
http://accessories.etrailer.com/trai...Power%20Module
This makes sense and is consistent with some other things I have read. Thing is, they appear to have installed such a converter as part of their harness. I'll have to take a closer look at how it is wired. In any event, this gives me a very good idea what to discuss with the installer, since their work is supposed to be under warranty. Thanks for the information.
There is a 4 feed to three output converter used when the vehicle has separate bulbs for turn and stop lamps but trailer uses the same filament in the bulb for both of those functions. This style converter does not have a battery supply, it still uses the power from tail, stop, and turn bulb circuits and triggers the overcurrent shut down.
Yes, that's probably what they installed. I finally got time to go back to U-Haul in Dartmouth, Nova Scotia. Turns out their computer system says my S60 does not need a power module, but they had another reference book that says it does. We tested it on their trailer with incandescent bulbs and the problem occurred, but when we tested it on a trailer with LED lights everything was fine. So, I was able to convince them that it was an overcurrent problem. They did not have a power module on hand, so they sent their guy down the road to buy one from the competition and they installed it while I waited. All I had to pay for was the difference in the cost of the part. Under $30 with taxes. It was a pain to have to go back, but I felt they did an excellent job of resolving my problem in a very timely manner. No appointment, and I was in and out in a little over an hour on what was obviously a busy day for them. Very satisfying. Thanks for your advice too.
Great.
Late models vehicles are using more electronics in circuits that are simple where you may not expect this.
My sister has a Ford Transit Connect little van thingy and she wanted to have a trailer to haul spare cargo (shows dogs and the crates fill interior). I added the hitch and trailer light wires. I tested everything and it worked. She went on a trip and called me and said her friends following her tell her the signals blink 5-6 times and quit and her tail lights were going on and off.
I had to add one of those external powered modules to it.
Volvos, yes. But Turkish built Ford mini cargo vans?