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Thread: SOLUTION - Using Off Road height while towing.

  1. 26th October 2013, 04:39 PM #1
    harlie's Avatar
    harlie
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    SOLUTION - Using Off Road height while towing.

    Hi guys,

    A discussion that comes up regularly is if it is possible to use off road suspension height while towing. As we all know by default it is not but I’ve done some testing and there is a couple of solutions for the early L322. I image other rovers to have a similar trailer ECU but this must be tested - this info is only valid for iBus equipped L322 Range Rovers.

    If you don’t have LED lights on your trailer, or you use a pulse shunt with LEDs the simplest way is to fit a switch in the iBus data line to the Trailer ECU (I actually removed the iBus wire from the harness plug at the trailer ECU for this test). This will remove the Trailer ECU from the network so other systems won’t know about the trailer. This has the following affects.
    * The suspension is not locked and all height changes work as if the trailer is not there
    * Rear parking sensors still function as if the trailer is not there – which is annoying.
    * Reverse light and rear fog lights will not work on trailer. Not connected in AUS...
    * reporting for trailer globe monitoring will not work (will not display CHECK TRAILER LIGHT message if a globe is blown). This does not work if you have a LED shunt anyway.
    * Brake, Tail and indicator function is unaffected.
    * as my trailer has a shunt installed I am not able to report on whether the flashing LED issue is solved – I’m sure they will still flash, the ECU is off the network but appears to be still functioning as normal.

    Another idea I was playing with was a new Trailer ECU. This is a pretty simple build and would work with LED trailer lights (eliminating the need for a shunt) but would also result in the above points being permanent. Issues are the proprietary plug required to make a plug and play solution looks like a hard one to find, so it would require hard wiring, and I’m not sure we would want the trailer ECU off the network all the time – everyday around town towing where off road mode is not required it would be nice to have the parking sensors disabled ect.

    Today I had a good chat with Graeme and he also has a great idea. A LED pulse shunt box installed between the trailer ECU and the trailer plug on the rear bumper that is smart enough to fool the trailer ECU into thinking the trailer is not there. This essentially would have the same functions as the replacement trailer ECU mentioned above but does get away from the proprietry plug. However it also has the same issues as above where the car never knows about a trailer.

    After a day of towing with the trailer ECU off the network I can report that having the rear parking sensors still enabled is bloody annoying, so the iBus has been plugged in again. Because of this I think any solutions that involve a new box need some way of reinstating the iBus – like a switch....
    L322 3.6TDv8 Lux
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  2. 26th October 2013, 06:21 PM #2
    Graeme
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    After having some time to think though and research what we discussed, I suspect you already have a useful enough solution with the switchable iBus wire and the shunt box, albeit fitted to the vehicle rather than a single trailer.

    To produce a box to be fitted after the trailer ecu to prevent LED pulsing and provide current limiting for short circuit protection, a programmed controller would be required along with 2 FETs for each light and a pcb with tracks heavy enough to withstand the possible 8A current draw if 4 stop lights are fitted. Whilst it may appear that the pulsing is only around 2V, it must be at least 6V to operate LEDs and would be expected to be 12V but for only a very short duration, hence the need for the programmed controller. Overall I now don't think there's sufficient reason to develop another box.
    MY21.5 L405 D350 Vogue SE with 19s. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi, RTK base station using LoRa
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  3. 26th October 2013, 07:56 PM #3
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    harlie
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    yeah, you're right, overly complicated when a switch + shunt box will cover requirements.
    L322 3.6TDv8 Lux
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  4. 26th October 2013, 08:28 PM #4
    Graeme
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    If disconnecting the iBus wire triggered faults, eg the BCU expected to maintain contact with the trailer ecu or the trailer ecu wouldn't power the lights then another way to stop the feedback would have been appropriate.
    MY21.5 L405 D350 Vogue SE with 19s. Produce LLAMS for LR/RR, Jeep GC/Dodge Ram
    VK2HFG and APRS W1 digi, RTK base station using LoRa
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