No power from 4 or 7 pin plug socket

[2013Ram1500base]

Hey everyone, old guy here hoping someone can help me out.

2013 1500 basic with 3.6L gas.

I can't figure out why there's no power coming from the trailer hookup. Looking for the problem, I had it running, with lights turned fully on, (not just auto). F29 and F30 fuses were good, I put in new ones anyway. Still no power at the connector in back. Tried it with blinkers, flashers, every way I could think but no power. I was checking everything with a multimeter, and to make sure the meter was working I put it on the fuse box and it showed correct voltage.

So I'm thinking there's a relay somewhere, or a disconnection between the power distributor (fuse box) up front and the plug in the back. Someone said there's a harness connector somewhere behind the front wheel well, but before I tear everything open to look, does anybody have any ideas what else I can check? Do I need to replace the plug unit? How do I check if it's bad, or just not getting power?
Thanks everybody in advance.

 

[HarryS]

Your truck has several relays, but before we go there, did it originally have the trailer brake and module? Did it ever work?

 

[BossHogg]

If all trailer lighting is non-functional I would suspect a ground issue between the truck and the trailer. The second would be the connector under the back of the truck that connects the to the trailer electrical outlets.

 

[2003F350]

Hey everyone, old guy here hoping someone can help me out.

2013 1500 basic with 3.6L gas.

I can't figure out why there's no power coming from the trailer hookup. Looking for the problem, I had it running, with lights turned fully on, (not just auto). F29 and F30 fuses were good, I put in new ones anyway. Still no power at the connector in back. Tried it with blinkers, flashers, every way I could think but no power. I was checking everything with a multimeter, and to make sure the meter was working I put it on the fuse box and it showed correct voltage.

So I'm thinking there's a relay somewhere, or a disconnection between the power distributor (fuse box) up front and the plug in the back. Someone said there's a harness connector somewhere behind the front wheel well, but before I tear everything open to look, does anybody have any ideas what else I can check? Do I need to replace the plug unit? How do I check if it's bad, or just not getting power?
Thanks everybody in advance.

If you're not getting power and the fuses are good, then I'd be looking at grounds and the wires between the fuse block and the plug. It could be as simple as things got disconnected at some point because there was a wiring issue (I had an old '95 GMC that someone just...unhooked the T-connector for the 7-way round on the back...I have no idea why, I plugged it back in and it worked just fine).

Did you buy this truck recently, or a while ago? If you just bought it, chances are someone installed the parts, couldn't get it to work because they didn't know what they were doing, and sold it. If you've had it for a while and it used to work, I'd definitely be looking at grounds and wiring, looking for bad grounds or pinched/chaffed wires.

I've also seen this be a computer/wiring issue. I don't think it affected '13s, but my FIL had an '03 2500. Lights worked fine on the truck, he had all running lights/brake lights and RIGHT turn on the trailer, but no LEFT turn. After a lot of investigation, it turns out that someone had had a wire break coming out of the fuse box for the left turn signal on the truck, and instead of fixing it properly they bypassed the fuse box and put in a fuseable link just to make the truck work. The dealer we took it to that figured it out had seen this several times, and the fix was to put a Ford computer in it that put the brake/turn signals back into one bulb on the truck (they were built as separate bulbs). This also fixed the issue with the trailer harness.

TLR - Check wires and grounds, and fix it properly if that's the problem. Don't half-donkey it and make it someone else's problem later.

 

[2013Ram1500base]

If you're not getting power and the fuses are good, then I'd be looking at grounds and the wires between the fuse block and the plug. It could be as simple as things got disconnected at some point because there was a wiring issue (I had an old '95 GMC that someone just...unhooked the T-connector for the 7-way round on the back...I have no idea why, I plugged it back in and it worked just fine).

Did you buy this truck recently, or a while ago? If you just bought it, chances are someone installed the parts, couldn't get it to work because they didn't know what they were doing, and sold it. If you've had it for a while and it used to work, I'd definitely be looking at grounds and wiring, looking for bad grounds or pinched/chaffed wires.

I've also seen this be a computer/wiring issue. I don't think it affected '13s, but my FIL had an '03 2500. Lights worked fine on the truck, he had all running lights/brake lights and RIGHT turn on the trailer, but no LEFT turn. After a lot of investigation, it turns out that someone had had a wire break coming out of the fuse box for the left turn signal on the truck, and instead of fixing it properly they bypassed the fuse box and put in a fuseable link just to make the truck work. The dealer we took it to that figured it out had seen this several times, and the fix was to put a Ford computer in it that put the brake/turn signals back into one bulb on the truck (they were built as separate bulbs). This also fixed the issue with the trailer harness.

TLR - Check wires and grounds, and fix it properly if that's the problem. Don't half-donkey it and make it someone else's problem later.

You gave me a couple great tips, thanks very much. I bought it 3 years ago but haven't used the trailer power connector before this. I'm pretty sure it's not aftermarket, I'm pretty sure it's factory installed. Through the bumper, next to the license plate. How can I check if it's a computer issue? I'm trying not to spend money on a mechanic, just to find something I could fix myself. Thanks much

 

[PaleFlyer]

You gave me a couple great tips, thanks very much. I bought it 3 years ago but haven't used the trailer power connector before this. I'm pretty sure it's not aftermarket, I'm pretty sure it's factory installed. Through the bumper, next to the license plate. How can I check if it's a computer issue? I'm trying not to spend money on a mechanic, just to find something I could fix myself. Thanks much

Generally, you would probably need to find the relay(s) that goes to the trailer connector, and see if the COIL side is getting power. If it is, the computer is likely fine. Then you need to see if the Common of the relay is getting power from the battery (it would be REALLY weird if it wasn't.) After that, check the relay. Kinda a PITA without a way to power it externally, and can't just assume a new one works, as sometimes relays are DOA. (Relays usually have at least 4-5 pins. 2 are the coil to "energize" the relay, as one is from the computer, the other is to truck ground/battery neg, then you have the common which is how the contact gets power from the battery, and a Normally Closed (meaning it has power if the coil is off), and Normally Open (No power if the coil is off). Best if you can somehow test the back end of the connector to see if the relay is "changing", but probably not easy. then you would need to go to the connector, and check if it has power. Multimeters do NOT put a load on the system, so it could get power under a multi-meter, but fail under an actual load. you also should have a known good piece of wire that you can use to complete the circuit for your multimeter to do a continuity test (resistance, but it beeps if the resistance is below like 5 ohms instead of just displaying "0.3") between the NO contact point of the relay, and the possibly faulty output of the trailer connector. This should ideally be done with the battery unplugged, as extraneous voltage to the test point could fry your multimeter during a resistance test, as the multimeter is supplying a known amount of power, and measuring the current draw, and the big honkin 12V 600+A battery is WAY more than the multimeter is built to measure during a resistance test.

As others have said, it's possible the fuse/relay box is fine, and even the computer could be fine, but you have ~20+ft of wire for each of the 7 signals going back to the back of the truck and any/all of them could be damaged somewhere along the run.

 

[2013Ram1500base]

Lots of great info, thank you very much