Help! Towing Electrical Trouble

Reply Subscribe

Thread Tools

Search this Thread

Nov 22, 2009 | 08:00 PM

andt350

Thread Starter

New User

Joined: Dec 2006

Posts: 16

Likes: 0

Help! Towing Electrical Trouble

Just bought a new Boat trailer with disc brakes. I was trying to troubleshoot why the backup light prong on my round trailer electrical connector on my F350 had no power to it for the back-up lights. The truck back-up lights came on but no power to trailer. I disconnected the trucks round plug assembly (male plug from harnes on inside of bumper to female plug on from outside of bumper to see if electrical power was coming through bumper mounted receptical. Tried starting truck to move it while I had the male and female parts disassembled and truck cranked over a couple times and died. Now I have whart seems like dead batteries and interior lights flashing at low power (dim) like 4-way flasher(flasher noise comming from the underside of dash). very strange. Any one give me a suggestion on this. Truck is useless at this point. Hope to hear from someone know;legable about electrical circuits for trailer towing device (round ford trilerd receptical)

Nov 22, 2009 | 08:52 PM

Mud Doc

Posting Guru

Joined: Nov 2002

Posts: 1,222

Likes: 4

From: Texas

Year of truck? Could you have let the power end of the harness contact the frame (shorted) when moving? Have you reconnected the harness and tried anything?
Are the battery terminals clean with good contact to the posts? Are all fuses good? Might also be 2 fuse blocks--one in the dash, one in the engine compartment.
Odd situation.

Nov 23, 2009 | 05:10 PM

andt350

Thread Starter

New User

Joined: Dec 2006

Posts: 16

Likes: 0

I charged the batteries all day and they did not take the charge. Right now, I open the door and the interior lights click on and off at the pace of a 4-way flasher (very dim) and I can hear the clicking sound from under dash around where the interior fuse panel is. Dark and raining outside and I have taken tomorrow off (supposed to rain some more) to see what I can figure. I am no good at electrical problems, but will try anyway. I am convinced (almost) that my working on the plug is coincidental and not cause. Seems like something failed/burned up and shorted to ground. I don't know, maybe a relay, or the starter itself. I can use any advice and suggestions anyone might have

Nov 23, 2009 | 07:02 PM

Mud Doc

Posting Guru

Joined: Nov 2002

Posts: 1,222

Likes: 4

From: Texas

Take out the batteries and have them checked--if one is dead, may cause the 2nd to have problem. Clean all terminals of corrosion. If batts good--dont think they will be if they wouldn't charge--hook everything back up and see if the lights work. If bad, get new ones and maybe problem will be solved. Might have a relay going bad also--the clicking--trying to reset. Other than this, you are looking at at tow to shop. Good luck.

Nov 24, 2009 | 11:17 AM

n4aof

Senior User

Joined: Jan 2009

Posts: 157

Likes: 0

Quote:

Originally Posted by andt350

Right now, I open the door and the interior lights click on and off at the pace of a 4-way flasher (very dim) and I can hear the clicking sound from under dash around where the interior fuse panel is.

This is most likely the result of the problem rather than being the cause of the problem.

I've never seen this situation in a Ford but I have seen this exact behavior in my former Jeep Grand Cherokee. When the voltage falls too low, the anti-theft system would partly trigger and would try to flash all the interior and exterior lights (it would also try to honk the horn but if the battery was low you wouldn't hear the horn). The same anti-theft system would also kill the ignition and starter circuits. With my Jeep all you needed to do was reset the anti-theft alarm and everything would be ok as long as there was enough battery voltage.

This may not be exactly the same situation, but the flashing lights are almost certainly related to an alarm system that is intended to flash the lights when the alarm goes off.

That doesn't account for how the voltage got too low in the first place. But I would definately try disconnecting the batteries from the truck while trying to recharge them. A couple of hours with no battery should give all the computers time to reset themselves and recharging the batteries while disconnected from the truck would prevent them being run down by whatever is wrong in the truck while you are trying to charge them.

Nov 24, 2009 | 06:29 PM

cdrmotorsports

Postmaster

Joined: Aug 2005

Posts: 2,992

Likes: 2

From: Lancaster, MA

I think n4aof is dead on with this one. I'd start looking at the batteries before anything else. There is no way that disconnecting the trailer plug could cause all this mess unless is shorted the whole computer out if it grounded on the frame. Basically it's highly unlikely. I had a similar problem with an old Ford Ranger I had. The battery got really low and the junky aftermarket alarm was trying to go off and had me worried for a while. Like he stated, try the batteries first before you get too worried. Good luck.