Welcome to Manins' truck camper project

ABS Defeat for Off-Road Driving

ABS (Anti-lock Braking System) is not very effective in gravel and snow, as it does not let the wheels lock under heavy braking. With no ABS you won't have control of the vehicle, but you will stop more rapidly if you just slam on the anchors. This is because the gravel/snow will pile up in front of the tyres, essentially creating a bow wave which will dissipate more energy than normal ABS braking in those circumstances.

On the Daily 55S17W ABS is disengaged when the centre differential lock is selected. However this puts more strain on the transmission and tyres and in any case the torque splitting that is part of normal all-wheel drive does a great job. It would be best to be able to turn off ABS and allow all-wheel drive on dirt roads. This can be done.

As discussed by Marcus Tuck, when the AFAM (differential lock management control unit which is under the driver's seat) wants to turn off the ABS it supplies an earth, on the green wire number 8142, to a particular relay coil behind the dash. By cutting this wire, inserting a protection diode and a switch to earth on the other side of the diode to the AFAM I can turn off ABS at any time. The 'ABS Failure' and 'ABS' lights come on when the ABS is turned off (in the same way as they do when the differential locks are engaged). If the centre differential lock is engaged the AFAM system still turns off the ABS automatically.

ABS-OFF_switch.jpg

Marcus Tuck cut wire 8142 at a point behind the dash, but as Don Incol found, it is easier to do this at the AFAM double-plug, under the rear of the driver's seat. The wire is labelled 8142 every few centi- metres so is not hard to find.

I use an OEM Iveco radiator fan OFF switch, relabelled as ABS-OFF, installed to the right of the steering wheel. It is illuminated whenever the switch is activated (as do the 'ABS Failure' and 'ABS' lights).

Ignition-switched 12 V power for the switch LED comes from a repurposed driver's seat-heater supply (see also here). A (7-core) cable taking the new earth signal and 12 V power was run under the floor matting to the chosen location on the dash. A local earth near the switch (on the lower door pillar) completes the circuit.

20170426_104021.jpg

The AFAM double-plug and cut 8142 wire.

201700426_20170426_120845.jpg

Diodes inserted into the 8142 wire and the switched earth signal wire.

20170426_134228.jpg

Switch with wires installed. Since a socket is not available, the wires are individually plugged using suitable crimped pins.

20170430_082319.jpg 20170426_143107.jpg

Left: the ABS OFF (defeat) switch is to the right of the steering wheel in the same switch group as the front flood lights.
Right: power sub-board behind drivers seat, supplied by the repurposed seat heater supply. A small fridge and the LED for the ABS OFF switch receive power when the ignition is ON.


LINKS