12v power at 7pin cable?

MikeW · 10-11-2021, 07:10 AM

Hello fellow Sunliners. I have a question regarding constant 12v power at my 7pin trailer lead. My 1997 Sunline Saturn 24ft does not have constant 12v at the charging pin. Everything works perfectly inside and out. Is there something with the inverter that prevents 12v battery voltage from feeding to the terminal? Has anyone else ever tested for this issue? It's silly but I discovered this while attempting the fuse jumper trick to see if my running lights would come on while parked in a site when unhitched. There is no power at the terminal when tested. Nor any of the other terminals as well. I'm baffled. 🤷*♂️ Fuses are all good. Battery gets maintaining voltage from the inverter as it should. Again, everything works fine. Just no power at the 7pin cable end. Thanks for any input.

mainah · 10-11-2021, 06:34 PM

Well good question it kind of seems the camper plug should not be powered other wise you could end up with a TV with a dead battery if it was plug in. Most modern TV's power goes off the the key for that very reason. Never gave that a though. See what you have done now I'll have to go have a look!

**JohnB** · 10-11-2021, 07:52 PM

Quote:

Originally Posted by MikeW

It's silly but I discovered this while attempting the fuse jumper trick to see if my running lights would come on while parked in a site when unhitched. There is no power at the terminal when tested. Nor any of the other terminals as well. I'm baffled. 🤷*♂️ Fuses are all good. Battery gets maintaining voltage from the inverter as it should. Again, everything works fine. Just no power at the 7pin cable end. Thanks for any input.

Hi Mike,

What you are describing is, the battery charge pin in the 7 wire cable connector is having issues being connected to the camper battery. And you my not be charging the camper battery off the truck either when towing down the road. That you may not have realized yet.

I know you said you checked all fuses, but what location did you check them at? The fuse panel on the power converter?

There is a separate fuse (normally a 30 amp fuse) for the truck charge line that it "not" in the power converter fuse panel.

On your 97 camper, up front inside the camper "somewhere" under a cabinet, bed, etc is a little wooden 7 wire cable junction box on the floor most times. There is a lid on top held on with a few screws. Find that junction box and check the truck charge line fuse for being blown in there.

If you can't find the junction box, then follow the 7 wire cable under the camper and look for where the heavy black cable goes up through the camper floor to inside. It will be above that location.

There is also a 30 amp battery charge fuse or a self resetting circuit breaker in that box. That 30 amp is between the power converter and the battery to protect the wiring from a short.

Have a look and see if that helps.

John

MikeW · 10-11-2021, 08:33 PM

I have already traced the harness into the trailer and it disappears into the front wall between the bed and the front of the trailer. There is no access door and from what I can tell the only way I could trace it into the wall is to cut a hole in it. Someone mentioned to me that it very well could have a battery isolator which could be a safety measure built into the system so that the terminal is not hot all the time. Sort of like a one-way solenoid. It would let a charge in but you can't get power out of it when disconnected. I don't know if that's possible with electricity but it's a thought.

MikeW · 10-11-2021, 09:16 PM

Quote:

Originally Posted by JohnB

Hi Mike,

What you are describing is, the battery charge pin in the 7 wire cable connector is having issues being connected to the camper battery. And you my not be charging the camper battery off the truck either when towing down the road. That you may not have realized yet.

I know you said you checked all fuses, but what location did you check them at? The fuse panel on the power converter?

There is a separate fuse (normally a 30 amp fuse) for the truck charge line that it "not" in the power converter fuse panel.

On your 97 camper, up front inside the camper "somewhere" under a cabinet, bed, etc is a little wooden 7 wire cable junction box on the floor most times. There is a lid on top held on with a few screws. Find that junction box and check the truck charge line fuse for being blown in there.

If you can't find the junction box, then follow the 7 wire cable under the camper and look for where the heavy black cable goes up through the camper floor to inside. It will be above that location.

There is also a 30 amp battery charge fuse or a self resetting circuit breaker in that box. That 30 amp is between the power converter and the battery to protect the wiring from a short.

Have a look and see if that helps.

John

FOUND AND FIXED!! I finally located the junction box where the incoming harness splices off to the rest of the trailer. It was under a hidden panel underneath my side table between the bed and the wall. Sure was tricky to find. In the mess of spagetti wires there are 2 12v leads that splice off the charging wire and both have individual 30a push-in fuses. guess which one was blown? Not sure why or how long it has been that way but it has been replaced and it is working as it should again. The constant 12v blade in the 7pin connector now has power just like i thought it should. Thank you all for the tips and thoughts on rectifying my issue. It is greatly appreciated.Feeling "charged" again lol

**JohnB** · 10-11-2021, 10:09 PM

GREAT!!!! you found it.

Super, Thanks for reporting back.

RVNewbie11 · 10-16-2021, 06:44 AM

Hi!

I went through this recently as well and replaced the "inline fuse" holders (near the battery) with ones that had rubber covers to keep the water out of them! I got them at a local O'Reilly's Auto Parts -- they have Orange wires and black fuse covers. You can get an extra one to make a test lead, to be able to safely activate all the lights and have fused protection while doing so. (They were 30AMP inline fuses holders.)

To put back together, I used outdoor wire nuts (they are light blue and available at home stores. I needed one large and the rest medium), filled each of them with even more die-electric grease and taped them like there was no tomorrow. I didn't have the fancy crimper used to make the factory crimps, but they seem to be back together tightly.

It may be much easier/faster to save the wiring that is there, on the current inline fuses and just snip them -- leaving as much length as possible, and wire nut to the remaining wires, instead of breaking open the existing connection points -- I regretted breaking them all apart and hadn't thought of doing it in this manner! You will only need small/medium wire nuts and you won't have to remake all the connections -- just the inline fuses connections -- 4 snips...4 wire nuts and done! (2 for each inline fuse holder).

I also made a little jumper (That I put an INLINE fuse in), to be able to activate the lights when not connected to a vehicle. One can take the little jumper and put it inside the 7-Pin harness and activate all the Clearance Lights / Blinkers / Reverse Lights, etc...

It was fun and I've fixed all the lights -- bought some new lenses and everything works like it should!

Putting a fuse in the jumper wire helps, so when/if you create a short, you pop the fuse.

The BLACK and the WHITE wires in the harness should NOT be jumpered together -- they will blow the fuses!

A super succinct and excellent video on this is available on Y o u t u b e and it helped me immensely! Listen carefully when he says which wires should NOT be be jumped together.

Look for video from Guy Presse: 7 pin plug on tow vehicle, how to test?

It will show you an example of the jumper lead and which pins do what.

His drawing was accurate and the video is short and sweet.

Shine on,

Mark in Massachusetts