I have a 1998 2500 with a towing package, which includes the factory trailer connector. When I plug my trailer in, everything works except there doesn't seem to be power going to the trailer battery charging terminal.

When I check the terminal with a voltmeter, (trailer not connected) I get about 1-2 volts with the engine either running or off. I recently took a 1200 mile trip, and don't believe the trailer battery was charged at all.

Any help and guidance would be appreciated.

Dan

 

You should be getting a constant 12 volts at the auxiliary power terminal, key on or off. 1 o:clock on the female. Check for a blown fuse link on the line up by the battery. Or just disconnect that line and rewire a direct line to the plug using a 15-25 amp fuse. Your trailer will only pull a couple amps unless discharged, I bet you weren't charging at all.

 

The factory 12V supply wiring is made to keep an emergency brake battery, (very small) charged. It is totally inadequate to charge the batteries in a fiver. If they were down even a little, and you plugged it in, it probably blew the fuse, as it should.

Check the trailer cable on the fiver. If it is 14/7, use a 15 or 20 amp circuit breaker in a 10 or 12 g wire to the power pin. Also check the fiver internally. Many of them don't have any fuse between the battery and the trailer connector. A short in the trailer connector typically burns down the fiver.

There's a thread on this site about a man that bought a fiver with a dead battery, and 100 miles toward home both the fiver and the truck caught fire and burnded down. I believe someone just put a heavier fuse, or maybe a no-blow in the trailer supply wire, and the fiver, as is typical had no fuse and a 14 g trailer lead.

My trailer feed is 6 gauge, through a 40 amp fuse. Trailer wiring is 8 gauge, except 10 G in the rubber cord. I added a 40 amp fuse to the circuit in the trailer.

It's also run through a relay that is driven by the heater and window auxiliary circuit. It is cpowered when key is in the run position, and no other time.

 

Thanks for the info Whiskers. I thought it was supposed to be a constant 12v on or off, but I wasn't sure.

Any idea what color wire it might be up front?

Is it part of the circuit that is marked 'trailer' with a 40 amp fuse in the box under the hood?

 

j_martin - I just have a small 20ft trailer with one deep cycle battery. The battery charged fine with my old tow rig, and I did check the trailer wiring, so I know the trailer wiring is fine.

I actually checked the truck wiring right after I got it before I even plugged in my trailer, so I'm just trying to see how the truck is supposed to be wired.

Thanks for the input!

 

I hooked a trailer up to my truck for the first time since I bought it, last week. The PO broke the cover off the plug on the truck! So things were a lot dirty and corroded. I applied electrical contact cleaner liberally. Trailer lights were behaving strangely. I looked at rear of truck and there was smoke coming out of the plug / connector. That was enough for me. I bought a swanky new truck end plug for $10. When I pulled the old plug out of the truck the wires were black and a couple of the lugs were rusted. How does that happen to copper? I cut all the wires back to clean copper and installed the new plug. $10 and an hour worth of my labor and all is good.

 

Copper and salt makes a black oxide that is neither conductive nor solderable.

The lug screws and clips in an RV connector are usually iron.

dpwilkie..... 40 amp circuit should have a minimum 8 gauge wire to work right, 10 g to prevent automatic flames. Somehow, after working on an older Dodge Ram pickup for awhile, I doubt the factory wire is that heavy. Just be sure it's suitable before you burn it down.

 

Sounds like you have an IPM. Could be a bad relay in it. Likely, power would be turned on to the trailer only when the engine is running, maybe even rotation required and seen by the PCM.