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thank TCP. I have actually done that (run the line from the front) but I put my relay in the back instead of the engine compartment... I actually am running 2 lines (both hot) and a ground on 10/3 cable to a box I installed in the jack compartment with a couple relays and the modulite. both hot lines have self-reset circuit breakers (along with a third CB for the brake controller that has a line going into the drivers side).

One relay is for the for ACC +12v as you mention (and I have also put a manual switch on the box to turn it off completely) and the other relay is for the reverse lights (in case I need them some day). I am looking to tap a location in the back to provide those relays with the signal they would need to trip the relay on when desired (ie key in ACC or IGN for +12V line and reverse lights on for the trailers reverse lights relay). Therefore I need to tap into something in the back to avoid yet another set of lines from the front (all be them smaller guage). The reason for putting the box and switch in the back is that is where I will likely be standing when I realize that I need to turn off the ACC 12V line and where I would go looking for the modulite if I had problems... so I keep all the "trailer" circuitry in one place and just feed it there.

You just tweaked my mind on something... I am powering the modulite off the same 10 guage powerline as the reverse lights relay... but that line comes right off the battery... its not connected to an ACC or ingition based circuit up front. Therefore the modulite and its wires (tail, turns and stop) are live even if key is out of ignition. Since they drive their signal from the vans lights... I assume thats ok but I wonder if I should have provided power to the modulite from an ACC based circuit and not the battery directly. Easy to switch in the engine compartment, just need to relocate that particular wire to an ACC based circuit in or after the fuse box insted of the battery connection... ) but is that normal? do you drive the modulite off switched power from the engine or is it powered 24/7 from the battery?
 

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If you're looking for a switched point in the back, I would try the rear power outlet (driver's side, above the wheelwell). I have a regular 12V socket there, but if you have 120V AC back there you won't have that switched wire. Not sure where to go from there.


robaer said:
thank TCP. I have actually done that (run the line from the front) but I put my relay in the back instead of the engine compartment... I actually am running 2 lines (both hot) and a ground on 10/3 cable to a box I installed in the jack compartment with a couple relays and the modulite. both hot lines have self-reset circuit breakers (along with a third CB for the brake controller that has a line going into the drivers side).

One relay is for the for ACC +12v as you mention (and I have also put a manual switch on the box to turn it off completely) and the other relay is for the reverse lights (in case I need them some day). I am looking to tap a location in the back to provide those relays with the signal they would need to trip the relay on when desired (ie key in ACC or IGN for +12V line and reverse lights on for the trailers reverse lights relay). Therefore I need to tap into something in the back to avoid yet another set of lines from the front (all be them smaller guage). The reason for putting the box and switch in the back is that is where I will likely be standing when I realize that I need to turn off the ACC 12V line and where I would go looking for the modulite if I had problems... so I keep all the "trailer" circuitry in one place and just feed it there.

You just tweaked my mind on something... I am powering the modulite off the same 10 guage powerline as the reverse lights relay... but that line comes right off the battery... its not connected to an ACC or ingition based circuit up front. Therefore the modulite and its wires (tail, turns and stop) are live even if key is out of ignition. Since they drive their signal from the vans lights... I assume thats ok but I wonder if I should have provided power to the modulite from an ACC based circuit and not the battery directly. Easy to switch in the engine compartment, just need to relocate that particular wire to an ACC based circuit in or after the fuse box insted of the battery connection... ) but is that normal? do you drive the modulite off switched power from the engine or is it powered 24/7 from the battery?
 

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Thanks again.

I grabbed a soft copy of the sienna repair manual last night and started looking over the wiring diagrams. I see that the 120V inverter is actually located back in that same compartment... (further forward before the drivers side rear wheel well down close to the door opening) and therefore if I pop that panel I will likely find the harness that has a bunch of IGN or ACC power circuits.

Unfortunately all diagrams in the manual show the perspective from the upper left rear looking down at van and this area is really congested for wiring... its really hard to see whether its in the wall, ceiling, floor or even other side at that point... but I am fairly confident is wall and low.

I also see the reverse lights run out of the hatch through a harness in the ceiling down that side and have the harness number and wire for that circuit. Will look and see if I can match it up in the same bundle and put a meter on it when I pop gear into reverse to make sure. That would mean one location for both... will take pics if it works for others who might be interested (since I have found nothing after trolling a lot of other forums for it)
 

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Here is a link to one of the "MODS" DIY. He was installing a back up camera. Now it shows panels off ETC so this may help you a bit. Reverse light wire is RED/BLACK.

http://siennachat.com/forum/index.php/topic,53.msg194.html#msg194

Also in his thread is "part 2" It shows more wires ;D

EDIT: last 3 post have been deleted to prevent confusion.
 

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robaer said:
I also am looking for where to tap in the Reverse lights. Since I don't need to open the hatch up, would prefer to tap into the harness somewhere inside the cabin. I heard that above the third row seating the harness for the hatch runs... anyone have any advice on what to look for when I open that up? remember the reverse lights wire colour?

Removing ceiling panels could have a low WAF (Wife Acceptance Factor) so I am trying to minimize time in the cabin and go at it with a plan.
Attached is a copy I made of a highly relevant post from the old site ... Check out the first reply (by our own BrianBP :D), and the third reply (by FloridaNative, another SiennaChat member ;)). I have also attached the two files that Brian posted since they cannot be linked to anymore :mad:.
 

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Those are great posts. The doc attachment was perfect. I think I will use the same connection points as Florida Native did. Cant wait to pop the panels now. Thanks so much for restoring those posts because there really is a lack of this detail on the interwebs and I expect there will be more "diy trailer guys" doing this. Super helpful to have them.
 

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This is a GREAT thread! The only thing I did not see addressed was the capacity of the '04 Sienna XLE alternator. The RV place I had hook up my 7-pin connector system would not run a 12V line for the battery/fridge system, as he said the alternator did not have enough Amp output. I only pull a Coleman/Fleetwood pop-up with electric brakes. Thanks. ???
 

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RidgeRunnr said:
The RV place I had hook up my 7-pin connector system would not run a 12V line for the battery/fridge system, as he said the alternator did not have enough Amp output.
I suppose if you are going to try welding with the 12V power line, then you shouldn't do it with a Sienna. On the other hand, it works fine to charge an RV trailer battery.

What did these people dictate was the minimum required alternator capacity? How much current did they say the trailer would use? My guess is that they also insist that only pickup trucks and large SUVs should tow, and that the Sienna can barely handle the pop-up. I don't put much faith in random retail "experts", but in this case it is surprising that they would pass up the opportunity to make more money by selling another service... or did they charge the same for the wiring without bothering to do the charge/power line?

In a conventional RV installation, this circuit connects the tow vehicle's charging system to the trailer's battery, not just directly to some unknown load. This trailer charge circuit only needs to keep up with the average of power used by the trailer (or less, since if the charging does not keep up the trailer battery just runs down), not the peak power used if lots of stuff is turned on in the trailer.

Also, the circuit must be protected by a fuse or circuit breaker (no larger than that appropriate for the wiring), which sets an upper limit on how much current might be drawn. Mine is 30 amps, but it is an auto-reset circuit breaker, so if it is tripping and resetting I wouldn't know, so I really don't know how much current goes to the trailer battery.
 

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All that plus the fact that line losses in wire running to the trailer have a bit of a self-regulating effect. The more current that is flowing, the more loss in the cabling which reduces the voltage at the trailer end and therefore charges the battery in the RV at a lower rate. The chances of ever seeing 30 amps in your average 10gauge or even 8 gauge wire over the 30-40 feet (remember current has to flow back from the trailer as well, it's an out and back journey) is remote unless there is very close to a short on the other end.

Generally the "charge" wire is more a maintenance wire for the fridge/monoxide detector and doesn't add more than a surface charge to the RV battery while driving. True charging of the RV battery requires AC/converter/batt charger to actually fill it.


brian_bp said:
RidgeRunnr said:
The RV place I had hook up my 7-pin connector system would not run a 12V line for the battery/fridge system, as he said the alternator did not have enough Amp output.
I suppose if you are going to try welding with the 12V power line, then you shouldn't do it with a Sienna. On the other hand, it works fine to charge an RV trailer battery.

What did these people dictate was the minimum required alternator capacity? How much current did they say the trailer would use? My guess is that they also insist that only pickup trucks and large SUVs should tow, and that the Sienna can barely handle the pop-up. I don't put much faith in random retail "experts", but in this case it is surprising that they would pass up the opportunity to make more money by selling another service... or did they charge the same for the wiring without bothering to do the charge/power line?

In a conventional RV installation, this circuit connects the tow vehicle's charging system to the trailer's battery, not just directly to some unknown load. This trailer charge circuit only needs to keep up with the average of power used by the trailer (or less, since if the charging does not keep up the trailer battery just runs down), not the peak power used if lots of stuff is turned on in the trailer.

Also, the circuit must be protected by a fuse or circuit breaker (no larger than that appropriate for the wiring), which sets an upper limit on how much current might be drawn. Mine is 30 amps, but it is an auto-reset circuit breaker, so if it is tripping and resetting I wouldn't know, so I really don't know how much current goes to the trailer battery.
 
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