I have a 2001 Ram 1500 4x4 Sport; I also have a 5' x 10' flatbed trailer with the 4-prong flat connector.

I have used this trailer for years with other vehicles with no problem. However, the first time I hooked it up to the Ram, whenever I had the headlights on and the emergency flashers going, I noticed that the truck's back-up lights flashed dimly; the trailer brake lights also did not flash in sync with the truck's brake lights.

The first time I used the trailer, it didn't take long before a fuse blew, leaving me with no dash lights, truck tail lights or any trailer lights. The fuse that blew is for the "Park Lamp" circuit in the PDB under the hood. I replaced it, and also replaced the plug-in trailer wiring harness that connects to the truck's tail lights. After doing this, with the headlights on and emergency flashers on, the truck's back-up lights no longer flashed and the trailer's brake lights flashed in sync with the truck's brake lights.

I thought the problem was solved. However, the next time I used the truck with the trailer, I didn't make it down the block before the "Park Lamp" circuit blew again (15 amps). I replaced the fuse with a 30-amp fuse (MISTAKE) and tried it again. This time, the trailer's lights stayed on, although very dim; the truck's brake lights weren't too bright either.

I decided that this wasn't the solution, and as I disconnected the trailer wiring connector, I noticed that it was very hot... so hot that the prong for one of the 4 wires pulled right out of the connector.

It seems obvious to me that the problem is in the truck wiring, not the trailer, since I've never had this problem with other vehicles. The lighting on the truck also functions perfectly when the trailer is not connected.

Any ideas as to what the problem might be, or how to start looking for it?

Thanks,
dta0251

 

I would start with looking for slightly cut wires on both the truck and trailer that might be grounding out and popping fuses.

 

remove the light bulbs in the trailer lights and test the wiring with an ohmmeter. no telling what the mice have been doing.

bear in mind that minus the trailer connector pigtail, the truck wiring is used every day, and its been ok until you've hooked up the trailer. so don't assume the trailer is good and the truck is bad.

 

You can also use a small 12 volt battery to test the trailer lights. When I rewire a trailer I use a 12V gell cell battery for testing. I use a fused lead on the + terminal. This way I can see what works and what may be a problem.

I made an adjustable power supply that I use for shop testing. I can go up to 5 amps and 1.5-24 volts if needed. Sure comes in handy.

 

Thanks to all for this helpful advice. dhvaughan, the reason I think that the problem is in the truck is that I have used this trailer many times with other vehicles with no problems. The trouble only started when I hooked it up to this Ram.

One thing I forgot to mention before is that the truck once had a keyless entry/remote start system installed. When I got the truck it only came with an ignition key; no keyfob for the keyless entry system. I assumed it was inoperative, so I removed all the hardware under the dash and hood and re-connected the wiring. The problem could be under there as well.

dta0251

 

Also, Don't assume that who ever wired the connector to your old truck did it in the same sequence as whoever wired the connector in the new truck. When you said that one prong got so hot that it melted out of the connector, that sounds like some voltage was feeding into a ground, and since you had a 30 amp fuse in there, it just didn't get hot enough to pop the 30. It just got hot enough to melt the rubber or plastic. As a general rule, you should never raise the fuse rating. Think of fuses as safety shut offs. A lot of current through a small wire makes for a bad day. Could even start a fire.
Anyway... from the truck side, take a test light and a friend and determine what each "prong" is feeding. Determine the right and left turn signals, brakes, running lights, etc. If on the trailer side the "prong" sequence doesn't match, then, there's your problem. Just rewire the trailer side connector to match the truck side. You could be just be crossed up on one or more wires.
Good Luck !!

 

Check and make sure the plug on the truck is grounded properly,sounds like the voltage is feeding back.

 

Just wanted to follow up on this thread. Last weekend I hooked the trailer up to a truck that had previously been problem-free... and it blew a fuse in this truck. So now it was abundantly clear that the problem was in the trailer after all, as some of you have suggested.

I bought a trailer wiring kit and proceeded to install it. Removing the old stop lights, it appeared that they had been installed "quick and dirty." The wires on one of them, rather than being run through the little groove provided, had been pinched between the light and the mounting bracket; and there was a place on one of the wires where there were some strands showing that probably came in contact with the bracket from time to time as the trailer bounced around, causing the short.

Anyway, I removed all the old stuff, carefully installed all the new stuff, hooked it up for a smoke test, and voila! Everything works great, no blown fuses, and I am a happy camper!

Thanks again to all for your input. I pledge to listen to it earlier next time!

dta0251

 

wow that seems alot worse than the problem i have

mine, the turn signals just flash real fast, i just need to put in a heavier flasher unit

 

Yeah, the older (94-97) trucks need a larger flasher if they do towing. I'll get you the Mopar P/N for the flasher tonight.