The yellow switch on the gear stick is Hill Decent Control. On the auto this is a yellow switch just behind the gear selector.
HDC was an option, but also standard on the higher models. Something most the later models had anyway. When in either first (1 on auto’s) or reverse gear, and you select HDC, the vehicle will use the abs to slow itself down, when ever you take you foot off the accelerator pedal. This is ideal for down hill descents where you’d use first low ration on your P38.
HDC hill decent control, ABS anti lock breaking system – 4 wheel independent, ETC electronic traction control and EBD electronic break force distribution all became standard on UK models 2001 onwards. The reason I mentioned this is it’s not always an option on over seas markets.
Recently I went down a frozen snow covered 150m slope at 15 degrees. 2 inches of snow. Put my auto in to first, selected HDC and went down. Took my foot off the accelerator and the ABS kicked in under orders from the HDC. Result was the car slowed down with several abs pulses. Then it continued on it’s own for 1 or 2 seconds then pulsed the abs once. Same thing happened 1 or 2 seconds later, then continued to the bottom with out ABS, even though HDC was still selected and available if it wanted it.
Even though the Freelander has the option to do the above, it’s never a cure for bad driving, or taking risks. Common sense and all that!
Taken from the Rave Disk:
Hill descent control
This feature allows the vehicle speed to be controlled during a hill descent using the vehicle brakes. This feature has to be selected using the Hill descent switch with the selected gear being 'first' or 'reverse' and the brakes below 35C. When HDC is selected by operating the latching HDC switch the green LED is illuminated continuously to indicate HDC is available. If conditions are not met to enable HDC operation, after the switch is operated the green LED flashes. When going downhill and HDC is selected the vehicle will maintain a target speed of approximately 7k/ph by applying the brakes if the throttle pedal is not depressed. When the throttle pedal is depressed the target speed will be relative to the throttle pedal position and the vehicle will go down faster at the new target speed. If the slope is not steep enough and the speed is less than the target speed, the vehicle will not accelerate to
reach the target speed. The HDC function is brakes intervention only. There are 2 LED's in the
instrument pack for the HDC function. There is a green LED, which indicates the status of the
HDC function and an amber LED which, indicates HDC system fault when illuminated fully.
Minimum target speeds with the throttle closed are 6 mph (9.6 km/h) in first gear and 4 mph (6.5 km/h) in reverse gear. The first gear target speed is decreased to 4.4 mph (7 km/h) if rough terrain or sharp bends (detected from ABS sensor inputs) are encountered while already traveling at the minimum target speed. Minimum target speeds are increased at cold idle to prevent conflict between the brakes and the engine caused by HDC trying to impose a lower vehicle speed than is normal for the increased engine speeds at cold idle. Minimum target speeds at cold idle are 7.5 mph (12 km/h) in first gear and 4.4 mph (7 km/h) in reverse gear.
During active braking, the brakes are operated in axle pairs on one or both axles. The braking effort is distributed between the front and rear axles as necessary to maintain vehicle stability. Distribution of the braking effort is dependant on direction of travel and braking effort being applied. To prevent wheel lock, anti-lock braking is also enabled during active braking.
The ABS ECU incorporates a fade out strategy that, if a fault occurs or HDC is deselected during active braking, provides a safe transition from active braking to brakes off. The fade out strategy increases the target speed at a low constant acceleration rate, independent of actual throttle position. If active braking is in operation, this causes the braking effort to be gradually reduced and then discontinued. The HDC information warning lamp flashes while fade out is in progress.
If the clutch is disengaged during active braking, the HDC information warning lamp flashes after a delay of 3 seconds. After 60 seconds, if the clutch is still disengaged, the HDC fault warning lamp flashes and active braking operation fades out. Freelander 2001 MY
To prevent the brakes overheating, the ABS ECU monitors the amount of active braking employed and, from this, calculates brake temperature. If the ABS ECU determines brake temperature has exceeded a preset limit, it extinguishes the HDC information warning lamp and flashes the HDC fault warning lamp to indicate that HDC should be deselected. If active braking continues and the ABS ECU determines that brake temperature has increased a further 50 C, it fades out active braking and disables HDC. After fade out, the HDC fault warning lamp continues to flash, while HDC is selected, until the ABS ECU calculates brake temperature to be at an acceptable level. This calculation continues even if the ignition is turned off, so turning the ignition off and back on will not reduce the disabled time. When the ABS ECU calculates the brake temperature to be acceptable, it extinguishes the HDC fault warning lamp and illuminates the HDC information warning lamp to indicate HDC is available again. The disabled time is dependant on vehicle speed; typical times at constant vehicle speeds are as follows:
Disabling of hill descent control and traction control after prolonged use
If the traction control or HDC has been active for a long time, the foundation brakes can get very hot and damage may occur to the brake components compromising braking efficiency. For this reason there is an ABS function which inhibits excessive use of traction control and hill descent control. The way this function works is that the ABS ECU calculates the temperature of the brakes using internal algorithms. If the first temperature threshold (35C) is reached then the amber TC LED and the amber HDC fault LED will start to flash. The green HDC LED will extinguish A flashing LED warns the driver that the brakes are getting hot (during this period the TC and HDC function is still available). If the second temperature threshold (40C) is reached then the LED's continue to flash but the functionality is disabled for both TC and HDC. If HDC is operating at the time then the functionality fades out gradually when 40C is reached. Vehicle functionality will return to normal after the brakes have cooled down to below 30C.
Some video's of what a Freelander can do in my signature.
