Check out the trailer harness wiring diagram for a 2001 Venture at:
http://www.my-chevy-venture.com/trailer-wiring.html

The 2000 may be the same.  Although the dealer MAY be able to tell you what
you have for equipment on your vehicle from your VIN, you should ask
specifically about the auxiliary transmission cooler, the heavy duty
suspension, the larger rated alternator, and the wiring harness.  Further,
the parts department at the dealer may be able to show you a diagram of a
trailer harness plug, and where you would plug it in (if you have the
harness in your vehicle).

Finally, any reputable RV dealer will be able to tell you about the harness
you have, and give you a quote on installing whatever you need (but you need
not have them do the work).  They are usually MUCH more knowledgeable than
the dealer about trailer wiring.

Greetings,

I hope that you don't mind me saying that I am uncomfortable with the
assumption that your vehicle has the necessary equipment to tow 3500 lbs.
Remember, there are two versions of your van - one with a 2000 lbs capacity
and one with a 3500 lbs capacity.  Please go to your dealer and talk with a
service advisor and find out for sure what you have before you make what
could be a costly guess.  FWIW, if you don't already have it,  a good
quality tranny cooler slightly larger than you will need should only run
about $150.00 installed at almost any reputable garage.  Believe me when I
say that's a LOT cheaper than paying to have your tranny rebuilt because you
overheated it.  I would also suggest an auxillary engine oil cooler as well
because the last thing you want to skimp on is cooling capacity, but I
personally don't see the need for a larger capacity alternator just to run a
few extra lights on your trailer and brakes that you only use briefly
overall.  So many people believe they can just install a hitch and a plug
and tow 5000 lbs with no problems.  Others think they can load their vehicle
to the gills with passengers and cargo and still tow the max trailer
capacity.  These are the folks you see in the waiting room at the local
tranny shop complaining to the shop manager and swearing it's all the fault
of the auto maker.

One thing that did cross my mind about the wiring harness you have is that
it could be one of the type that plug in-line into the connector for your
brake lights and provide you with a 4-wire trailer connection.  Lots of web
sites sell them (including J.C. Whitney) and they are very easy to install -
just disconnect your factory brake light plug under the rear end of your
van, insert the adapter plug (it looks like a "T") and reconnect the
harness.  The wiring from the bottom of the T goes to your camper's plug.
It is possible to use this type of T-connector to provide power to the
designated pins for brake and running lights on a 7-wire trailer connector,
and is much cleaner, easier and more sure than splicing wires individually.

If you are looking for it on your truck, the wire for power to the trailer
brakes is usually blue.  Look near or inside the electrical center box under
the hood as well as under the rear end of the van for a disconnected blue
wire and that will be the one.  If you do end up running the wire for the
trailer brakes yourself, then use the largest gauge wire you can (smallest
number, for example 12g wire is thicker than 20g wire).  This wire usually
ends up handling high amps and is a pretty long run, so a larger diameter
wire is just a safeguard against it overheating and failing when you need
the trailer brakes the most.  If you do end up installing a hard-mounted
7-wire plug on the back of your van, then you can always use a one-piece
7-to-4 adapter that you can buy for less than $10.00 at any Wal-Mart for any
smaller trailer you may tow with a 4-wire plug.

Here's one thing you should pay attention to - if you don't have the
necessary wiring for trailer brakes and lights already run in your truck
from the factory, then it's a good possibility that your van does not have
the towing package.  All tow prep packages that I know of at least come with
wiring for trailer lights and brakes - it's not logical to advertise a
vehicle as having a tow package if it doesn't have the wiring already in
place at a minimum since it's the simplest (and cheapest) thing for the
manufacturer to provide as part of the package.  I can't imagine shelling
out an extra few hundred dollars for a tow package and not getting the
wiring, which costs the manufacturer next to nothing to begin with.  BTW,
you may also need a heavier duty flasher for your turn signals since you
will be adding more lights to that circuit and the standard duty electronic
ones may sense a fault if there is any extra load on the circuit.

Good luck and let us know what happens - Jonathan

Any source for that?  I have the impression that requirements for
trailer brakes start at 1500 pounds most places.  But I could very well
be wrong.  That's why I'm asking for a source.