New to Astro-How does trailer wiring work?

[nathanj04011]

I just purchased a 2004 Astro LT with the "factory installed" trailer wiring. I say that because in the jack area in back, there was the 7 pin wiring, all nicely taped and such. Previous to the Astro, I had a Jeep, and there are several differences I noticed immediately after getting a Curt hitch and 7 pin plug hooked up today.

One was that when plugged in to the trailer wiring, the "running" lights on the trailer came on, irrespective of whether or not the lights in the Astro were on. I'm assuming this is due to the daytime running lights on the Astro?

A second thing is that when the ignition is turned off, it appears that it kills the power back to the trailer? Again, is this normal, as the Jeep would power the trailer until its battery was dead?

Thirdly, if the battery on the trailer is dead, will that prevent the Astro from powering things like the fridge and 12v lights and such? That is apparently happening, and I don't know if it is not wired correctly, or if that would affect the way the trailer gets power.

Thank you very much for your help!!

[Jasen]

Welcome to A/S

Someone will be by shortly to lend a hand. In the mean time please step back up onto the curb for your own safety

[Astroplane]

What are we working on? A travel trailer?

One was that when plugged in to the trailer wiring, the "running" lights on the trailer came on, irrespective of whether or not the lights in the Astro were on. I'm assuming this is due to the daytime running lights on the Astro?

That sounds like what is happening.

A second thing is that when the ignition is turned off, it appears that it kills the power back to the trailer? Again, is this normal, as the Jeep would power the trailer until its battery was dead?

Do you want it to drain the battery? Do you have dual batteries on the van? Deep cycle and starting?

I don't know if it is not wired correctly,

It may be. I'm wondering if the Jeep was wired correctly or maybe wired to work for this application.

[nathanj04011]

Sorry, it is a 17' travel trailer with it's own battery, converter and such. I have just heard that if you leave the 7 pin plugged into the tow vehicle, it will drain the tow vehicle's battery and since that was happening on the Jeep, but maybe not the Astro, I was wondering if the Astro did not allow that to happen, or if the wiring was hooked up incorrectly, as it seems to cut the connection to the trailer when the ignition is turned off. Thanks for your help!

[Astroplane]

Hopefully another member will chime in here. Since you have a dedicated battery in the trailer, I would want the tow vehicle to shut off power supply from the battery with ignition off. That way you always have the option of starting the van if the trailer battery drains.

[tedanderson]

You probably have your running lights connected to the constant 12V lead. On the 7 pin connector, one of the wires gives you a consistent 12V+ lead for charging the trailer battery and any other on-board accessories. It gives you 12 volts when the key is on, and nothing when it's off. Observe the following:

TrailerDiagram.jpg (50.74 KiB) Viewed 11715 times

[hdldddpd]

My 2005 Astro is close to the attached diagram with a couple exceptions.

I have 8 wires in my harness. Seem to have an extra white #16 wire. Do I hook the #16 white to the same terminal as the other #10 white or what is it for?

My colours vary too:
where the diagram shows I Have
DB - Brakes not sure
W - Gnd W
Y - Left Y
BK/LG - Backup LG
BR/W - Running Lts BR
O - Battery O
DG - Right BK/G

Are these differences common or are there differences between the 2004 and 2005 harness. Or maybe the part number is different? Any help would be appreciated.

[$uperJoe]

do you have a test light or meter? you could test each wire for function. your last wire might be something different such as reverse lights. some larger trailers have back up lights. it is important to set up the plug correctly as it may be used with a different trailer and would not want to risk problems with either the van or trailer in that case. the plug has a standard so i would recommend the diagram ted shown. this is how i was taught to be correct. i am by no means an expert in trailers but have seen some very interesting "inventions" as wiring goes over the years

[Miserly Man]

Now, for the exciting stuff.

I finally fished out the towing harness with my factory "tow package". Now, for those that know all about this, feel free to skip ahead.

Turns out, whoever designed the towing harness was either the "Good" engineer or managed to avoid the bean counter. Either way, the tow harness is *****'. Now, to be perfect, there would be a hole with a grommet in the side-and maybe there is-but I didn't see it. Here is what I saw.



There is a hole but it leads to under the bumper. I could feed it down there and then drill a hole in the bottom and put in a grommet. Don't know yet.


So, onto the treasure trove known as the "taped wire". Somewhere back in 2002, a UAW employee wrapped this treasure of wiring with care. At first, I thought there was just the standard 4...wait...5 wires?



Well, this is odd...my 4runner had only four...and now there are five. Time to break out the wiring diagram. Hmm....what do we have here? More wires?


Hmm, let's pull back more tape. What do we find here? Woot!


Bingo! A switched and unswitched hot 30A connection! Just when you hate GM, this little treat shows up! Now, time to wire up a RV blade.

So, a quick read of my owners manual read (duh, should have checked first) a total of 8 wires. L

[redfury]

I've got the same thing, except mine has a 4 blade standard connector and then some brick with 6 connectors ( most likely not all hooked up, but when it was all taped together, the brick is set back about 6 inches. I've never seen the connector before, but there is the other end of it in the original packaging in the jack storage....I'm going to get the RV blade and wire it up properly under the vehicle so I don't have a 4 foot mess of black tape and wire just laying out in my cargo area.

[vandodge]

You posted some great pictures. But I was hoping to see a picture of the final splice. Did you use the large diameter white wire or the smaller for your ground connection to your 4 wire plug?

I have the BROWN connected to the trailer running lamps (brown to brown)
I have the Dark GREEN as the right turn signal Green to Green)
I have the YELLOW as my left trun signal. Yellow to Yellow)
I had the small WHITE as my ground but keep blowing fuses when I hit the brakes or use the turn signals. I read elsewhere that the small white wire is a high mount brake light lead.

Thanks

[Leeann_93]

• Brown: Rear lamps.
• Yellow: Left stoplamp and turn signal.
• Dark Green: Right stoplamp and turn signal.
• White (Heavy Gage): Ground.
• Light Green: Back-up lamps.
• White (Light Gage): Center High-Mounted Stoplamp.
• Blue: Auxiliary circuit (eight-wire harness only).
• Orange: Fused auxiliary (eight-wire harness only).

You need the heavy gauge white as ground. Light gauge white is the high-mount brake light.