Hello,
This is my first post. I have searched the site so I hope this is not
a duplicate post. Sorry for the length. Just trying to be complete.
I recently purchased a new boat trailer with disc brakes. The brakes
are surge brakes. The system has a 5th wire (blue) that is to be
wired into the backup light circuit. This wire supplies power to a
solenoid in the brake system to release the brakes when backing up.
The backup lights in my vehicle (2002 Ford Escape) are activated by
closing a switch to ground when reverse is selected. The + side of
the backup ligh is hot when ever the ignition is switched on.
I researched the issue on this site and found how to wire a relay to
use the negative trigger to supply power to the brake solenoid.
I ran a fused 12 volt line from the battery and connected it to
terminals 86 and 30 of the relay. I connected terminal 85 to the
negative side of the backup light and 87 to the blue wire to power the
brake solenoid.
After connecting all the wires I checked the voltage and everything was
working as it should. I was only checking the output voltage, I did
not have the trailer connected. I then tied it all up with wire ties
and the next thing I knew, I had 12 volts on the output side (blue
wire) all the time even with ignition off. But the backup light was
not lit. The backup light continued to work as it should but the
trailer wiring had power through the relay all the time. Somehow the relay
was getting a ground, yet the backup light was not seeing the ground.
I thought I had fried the relay but after disconnecting it and
testing, it works as it should. I tried it all over again and the
same thing happened.
How is the relay seeing a ground when the backup light is not? What am i missing here?
Thanks for you help
-------------
John W.
Farmington,Mi
Disconnect 85. 1) Is the relay still misbehaving?
2) Is that wire you disconnected at 85 seeing a constant ground?
3) Or does it only see a ground when you go into reverse?
1) Have you connected to 87a rather than 87?
2) If yes something wrong with your wiring or you have a short.
3) Diode 1N 4004 across the relay coil, band towards 86. Also line diode same type on 85 wire, band away from relay.
-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.
Thanks, will disconnect 85 and check relay behavour.
Wire to 85 is connected to backup light ground and only sees ground in reverse. I put it in plastic loom to protect it.
-------------
John W.
Farmington,Mi
if you check, term 85 will show a ground with vehicle off, that is triggering the relay. can't connect term 86 to battery, needs to be connected to same power feed as reverse lights. you could connect terms 85 and 86 to the wires at the reverse light...orange / YELLOW +12 volt ignition, BLACK/ pink reverse (neg). or you can also find both at fusebox in left kick panel, they are in the same connector.
mark
Mark,
I was wondering if it might be better to separate the circuit that powers the coil from the power feed. Iwill give this a try. Thank You
John
-------------
John W.
Farmington,Mi
I did as Mark suggested. Wired the relay coil to the back up lights (85 and 86), ran the power supply to 30 and took power off at 87. It all works fine now. Thanks
John
-------------
John W.
Farmington,Mi