Originally Posted by Rickl
When I mentioned vehicles that had red directional signals, I was trying to describe vehicles that had dual filament bulbs like the "1157" bulbs. The brake and turn signal are combined into the "bright" filament and the taillight would be connected to the "dim" filament of the bulb.
Yes, that's the standard setup for trailers and "American" tow vehicles.
Trailer lights can be connected directly to these type of vehicles without a converter, but the extra lights on the trailer can almost double the original current. For vehicles with LED rear lighting, trailer lights could increase current load by four times normal. At the very least this often causes the turn flasher to operate at a higher than normal rate.
Yes I've seen the high flash rate even with filament bulbs on the tow vehicle. The solution was a Heavy Duty flasher.
Another risk is that a bulb shorting out on the trailer will kill all the lights on the vehicle. This could happen for example when backing a boat trailer into the water.
Yep, or with many other short-out scenarios such as pinched wires.
I was thinking it would be a great idea to design a transistor switching module, which would use the signals from the vehicle to turn on the power to the trailer lights. The power for the trailer lights would come from a totally separate 12V supply, which would protect the vehicles lighting circuit. I believe that this is what is already occurring in the amber turn signal converters. I was just wondering if this thing was already commercially available.
Don't know that it is but I used to make my own with a couple of relays. Gave me complete isolation.
If I understand correctly, your harness is connected directly to your taillights, with a fuse in each individual light circuit. In that case your F-250 might have a 20 AMP fuse for the brake lights, and your brake lights draw 15 amps normally and an additional 10 amps with the trailer connected. Placing a 15 amp fuse in the trailer harness would not keep the 20 AMP fuse from blowing. Or maybe you are saying that the F-250 is wired at the factory with a completely redundant lighting circuit for trailer lights.
Well, almost. The outputs from the left & right Stop/Turn switches are fused thru two additional 7.5A fuses to the trailer connector. For the parking/clearance lights battery power gets to the trailer connector via a separate 20A fuse and the NO contacts of a relay whose coil is energized by the headlight switch.