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bocotim 10-29-2011 10:59 AM

Should interior lights work with no battery but with Tow Vehicle connected
 
Should my interior trailer lights work when the trailer is connected to the tow vehicle (engine running), but the trailer battery is not connected?

I just replaced a flat 4-pin tow connector on a new TV (2008 Nissan Pathfinder) with a round 7-pin connector from Nissan that is compatible with the plug on my 2008 Airstream Bambi. I connected it to the trailer with the engine running on my TV but no battery connected on the trailer.

Trailer running lights work, signals work, trailer brakes work, etc. However, the interior lights/power in the camper do not work unless I connect the trailer battery. Should the interior lights work even though the trailer battery is not connected?

Thanks.

Tim
Boulder, CO
Airstream Camping

wkerfoot 10-29-2011 11:04 AM

Yes, as long as the charge line on the trailer plug is connected on the tow vehicle. Check for voltage at the truck end of the trailer plug.

A four pin plug does not have either a charge line, a brake line or a backup light line.

Bill

Quote:

Originally Posted by bocotim (Post 1065450)
Should my interior trailer lights work when the trailer is connected to the tow vehicle (engine running), but the trailer battery is not connected?

I just replaced a flat 4-pin tow connector on a new TV (2008 Nissan Pathfinder) with a round 7-pin connector from Nissan that is compatible with the plug on my 2008 Airstream Bambi. I connected it to the trailer with the engine running on my TV but no battery connected on the trailer.

Trailer running lights work, signals work, trailer brakes work, etc. However, the interior lights/power in the camper do not work unless I connect the trailer battery. Should the interior lights work even though the trailer battery is not connected?

Thanks.

Tim
Boulder, CO
Airstream Camping


bocotim 10-29-2011 11:14 AM

Quote:

Originally Posted by wkerfoot (Post 1065451)
Yes, as long as the charge line on the trailer plug is connected on the tow vehicle. Check for voltage at the truck end of the trailer plug.

A four pin plug does not have either a charge line, a brake line or a backup light line.

Bill

Thanks - I suspect you are correct, and I will test that. I swapped the out the 4-pin harness with the 7-pin (pretty much "plug-n-play"), but do I also need to do something extra to get the charge wire active? Is this a job for the pros?

Thanks!

Tim

Silver Goose 10-29-2011 11:18 AM

How many wires are on your harness on the TV. The 4-pin provided left turn/brake, right turn/brake, tail/marker and ground. The 7-pin adds backup/aux, electric brake controller and battery charge. On some vehicles, the battery charge line is only hot when the engine is running (often a relay is used to prevent the trailer from draining the engine start battery). Check that pin on the TV 7-pin socket with a test light or meter. If that wire is dead with the engine running, you may need to install a fuse or relay on a fuse box to activate it.

Inland RV Center, In 10-29-2011 11:20 AM

Quote:

Originally Posted by bocotim (Post 1065455)
Thanks - I suspect you are correct, and I will test that. I swapped the out the 4-pin harness with the 7-pin (pretty much "plug-n-play"), but do I also need to do something extra to get the charge wire active? Is this a job for the pros?

Thanks!

Tim

A wire is run from the tow vehicle battery, thru a 30 to 40 amp 12 volt circuit breaker, that is self resetting.

The wire size should be at least a # 10.

That wire then goes to the charge line terminal on the connector.

Do not use a fuse, but do use a DC circuit breaker.

Andy

ROBERT CROSS 10-29-2011 11:25 AM

Does the TV charge wire go thru the converter?, I thought it was wired directly to the battery, with no bat no power.:huh: Rong? ;)

Bob

Silver Goose 10-29-2011 11:28 AM

1 Attachment(s)
This may be useful.

Splitrock 10-29-2011 11:36 AM

If towing without a battery, the breakaway switch won't work in the event of a disconnected hitch. For testing, the interior lights should work without a battery if the tow vehicle 7-way is plugged in and wired correctly. My trailer uses all 7 connectors in the 7-way. A quick way to check the 7-way is to pick up a 7-way tester at the auto parts store. Not expensive.

I reversed the 7-way tester when I wired my trailer plug.

Silver Goose 10-29-2011 11:55 AM

Quote:

Originally Posted by ROBERT CROSS
Does the TV charge wire go thru the converter?, I thought it was wired directly to the battery, with no bat no power.:huh: Rong? ;)

Bob

Bob, I believe the TV charge line, the (+) post of the battery and the output from the converter are all tied together at some point so if his TV charge line is hot he should have 12v available in the trailer. If the TT battery has gone MIA, he should wrap the free end of the red battery cable with a rag or something to keep it from accidentally grounding out.

The battery disconnect switch could also be the culprit. It does isolate the house battery from the converter (and house 12v circuits) when in the storage position. If the TV charge line is tied to the battery side of the relay as I suspect it is, then the switch would need to be turned on.

bocotim 10-29-2011 03:11 PM

Quote:

Originally Posted by YankeeDoodle (Post 1065458)
How many wires are on your harness on the TV. The 4-pin provided left turn/brake, right turn/brake, tail/marker and ground. The 7-pin adds backup/aux, electric brake controller and battery charge. On some vehicles, the battery charge line is only hot when the engine is running (often a relay is used to prevent the trailer from draining the engine start battery). Check that pin on the TV 7-pin socket with a test light or meter. If that wire is dead with the engine running, you may need to install a fuse or relay on a fuse box to activate it.

The 7-pin harness that I installed has 3 cables (with multiple wires) that connected into plugs on the underside of the truck. I just tested with a voltmeter and everything seems to be working (electric brake, running lights, signals, etc.) except the charge wire (even with the engine running). I have to do a little more research to figure out how to activate it on a 2008 Nissan Pathfinder....

Thanks all for the pointers and help!

Tim

overlander63 10-29-2011 05:21 PM

The way it is supposed to work is you have to turn the battery disconnect switch on inside the trailer. If you don't energize that solenoid, the battery won't charge off the TV charge line, nor will the converter charge the battery whe it is installed.

bocotim 10-30-2011 06:07 PM

Hey Folks,

Just to follow up - I did a little more research and it looks like I just need to activate a relay located under the hood of the tow vehicle on the Nissan Pathfinder. I am hoping to talk to the Nissan service department tomorrow to confirm and get the part I need.

Here's a picture showing the 2 relays that I need. Only one of them is active, which is why (I believe) the brakes, signals, running lights are working, but the charge wire is not.

https://docs.google.com/document/d/1...SFV-X2Nj0/edit

Tim
Boulder, CO
My Airstream Blog

bocotim 11-03-2011 10:06 AM

For what it is worth
 
2 Attachment(s)
Just to summarize this information for anyone trying to add a round 7-way towing harness to a 2008 Nissan Pathfinder:

Installing a 7-way towing harness ($66 from a Nissan dealer) is very straight forward. It is mostly just a matter of plugging in a couple connectors under the rear of the Pathfinder and bolting on the plug. I don't have much skill/experience with automotive repairs, and this was a fairly easy project even for me. It took me about 45 minutes. The following instructions that I found on the web were extremely helpful:

Photo Installing OEM 7 min trailer wiring harness on a 2005 pathfinder - Nissanhelp.com Forums

I also needed to install 2 towing relays near the battery of the Pathfinder. Surprisingly, they do not come with the harness. One of them (Towing relay 1) was already installed to activate an existing flat 4-pin harness, but I also needed the second to activate the full functionality of the 7-pin harness, specifically, the charge wire. I purchased Towing Relay 2 (Part number: 25230-7996A, $38) from a Nissan Dealership here in Boulder, plugged it into the socket next to the tow vehicle battery, and now the charge wire is active when the truck is running.

Total cost for the 7-way tow harness and second relay was ~$105 with tax, but I'm pretty sure this could have been done more inexpensively if I hadn't gone through the dealership. Also, of course, I had to install a brake controller to operate the trailer brakes, which was a separate project.

Anyway, hope this information helps.

BocoTim
Boulder, Colorado
My Airstream blog: Airstream Camping


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