Thread: Tow Mode

What are you trying to achieve?

Trying to activate tow mode, or does that only work on the older ones?

Trying to activate tow mode, or does that only work on the older ones?

Originally Posted by breeze91

I have read about load resistors for tow mode. I initially installed 5w resistors in each indicator on the trailer with no change in dash. Then I got a 21 resistor and fitted it in one indicator. Still nothing.
Then I bought 25w resistors and put one on each indicator (caravan) and still nothing.

Any clues? We have done just over 1500km of our 4500km trip and it tends to lug a bit even in S.

Thanks

Are you saying you don't see the green trailer icon on the dash when the trailer / caravan is hitched?

Load resistors must be installed in 'parallel' to the trailer indicator lights. Are you sure you have them installed in that manner.

Perhaps you have installed them in 'series' with the trailer lights instead.

Originally Posted by breeze91

Hi Guys
I have a 2015 hse sdv6.
I have read about load resistors for tow mode. I initially installed 5w resistors in each indicator on the trailer with no change in dash. Then I got a 21 resistor and fitted it in one indicator. Still nothing.
Then I bought 25w resistors and put one on each indicator (caravan) and still nothing.

Any clues? We have done just over 1500km of our 4500km trip and it tends to lug a bit even in S.

Thanks

Resistors are measured in both power Watts, and resistance ohms. Just increasing the power rating won't change anything.

The car needs to "see" the correct resistance, ohms. The power rating, Watts needs to be matched to the power drawn by the circuit.
Which if the van has LED lights won't be much.

There are lots of threads on this in the D3/4 section.

I thought the resistors in the trailer circuit just made the trailer lights work properly and the dash tell tail work, are you sure it triggers and vehicle/gearbox/engine change? That said I drive a Defender so old and dumb, none of this matters.

Tony

Originally Posted by TonyC

are you sure it triggers and vehicle/gearbox/engine change?
Tony

Yes, it does. The BCM pings the indicator circuit for resistance which it will find if incandescent trailer lamps are in the circuit. The only visual indicator for the driver is the trailer symbol being lit when the indicators are activated.

Originally Posted by DieselLSE

Yes, it does. The BCM pings the indicator circuit for resistance which it will find if incandescent trailer lamps are in the circuit. The only visual indicator for the driver is the trailer symbol being lit when the indicators are activated.

Thanks for that.
What changes are made in tow mode?
Just gear changes?

Tony

Originally Posted by TonyC

Thanks for that.
What changes are made in tow mode?
Just gear changes?

Tony

Hmmm... I'll have to RTFM. The major one appears to be Trailer Stability Assist as detailed below. Other functions affected include:
Off Road Height will not be automatically selected by the Terrain Response system if a trailer is attached. But, of course, you can select it manually.
The Reverse sensors are disabled with a trailer attached. Front ones still work.
The car won't automatically lower if travelling over 130mph!
I can find no specific reference to gearbox or brake settings, but as the car tows a trailer as though it's not there, I can only assume it's all just part of the software.
Trailer Stability Assist
When the trailer electrical socket is connected, trailer stability assist operates automatically to enhance the existing DSC and terrain response functions of the vehicle when towing. The system detects sway movements caused by trailer oscillations at speeds in excess of 60 km/h (37 mph) and acts to eliminate them. It does this through braking and engine management. Braking management counterbalances the sway movement through symmetric and asymmetric braking, thereby slowing the vehicle and eliminating the oscillations. Engine management adapts engine torque output to support the braking management in stabilizing the vehicle and trailer.
Typical conditions when sway can occur include:
Changing highway lanes.
Traversing a lengthy bend.
Acceleration.
Braking.
The capability of trailer stability assist to respond early to the beginning of trailer-sway makes the system almost unnoticeable under normal driving conditions and keeps the vehicle and trailer under safe control. Trailer stability assist requires no input from the driver and operates up to the maximum vehicle speed.
Trailer stability assist will not operate while DSC is switched off.