Thread: Classic Cruise Control

I've got a 94 Disco (MY95) and just went through my cruise control system. I assume it is similar if not the same as on your RRC.
There is a very good step by step testing procedure in the RAVE manual in the electrical section.
In my case it turned out the cruise ECM was not receiving the signal from the 'set' switch. I swapped the two set/decelerate switches around and it now works but that switch is not 100% either.

The switches in the steering wheel both work, I forgot to put that in the 1st post. I have just finished downloading the rave CD so i will look it up now. The worst part about looking for this problem is I've seen how much of a mess the wiring behind the dash really is. time to get the side cutters out I thinks.


cheers

HELP! Could someone please show me a pic of what the cc ecu looks like?

it appears it is not where it belongs, but I cant find any connectors to say it has been removed

cheers

From Range Rovers Net.
Cruise Control If the cruise control malfunctions it is worth checking to see whether the brake lights are working; if both bulbs are blown the cruise control system becomes open circuited and ceases to operate.
Another failure point was experienced by Brad Crittenden on his 1990 Range Rover. A vacuum pump controls the cruise control diaphragm (simply a rubber bladder with a spring in it) which hooks up directly to the throttle linkage. If the diaphragm cracks it won't hold vacuum and the cruise won't work. The diaphragm (black and a little smaller than a tennis ball) is mounted on top of the engine toward the rear with one vacuum hose leading to it. To test, remove the vacuum line, compress the diaphragm, and place your finger over the vacuum line input. If it holds the vacuum (stays compressed), the diaphragm is OK; if it reinflates, it has a hole in it. A replacement is about $80; patching the hole, if one is found, might be worth a try.

Regards Philip A

The brake lights all work, and have found the unit, but it is different to the one in the rave manual. this one is an aluminium cased unit with 8 pins, not 15. I can whack a multi meter on it and i can get voltage, but without knowing what each pin does, I cant work out the problem.

Thanks anyway phillip, ill start trawling the net for a diagnostic procedure
Cheers

Just my experience with a Command cruise control.
In the Command units the solonoids that control the opening and closing of the dump valves are the main failure point.
It seems to me that all cruise controls will work in a similar fashion.
You can test the solonoids by jumping them with 12V , but do it quickly just enough to see if they click, as they usually run on 5V.
In a Command they are located in the housing of the vacuum motor that pushes and pulls the linkage via the diaphragm.
Regards Philip A

the vacuum pump and dump valve both work, i tested them yesterday and have located the fault to the ecu or associated wiring, but it appears there is not too much info on the the cc ecu. The rave manual for the 1995 rr has a different cc ecu, so I cant use that test procedure, if you have any info on the test procedure for the hella crusie control unit id greatly appreciate it.

edit: this is what i have worked out so far:
Pin NO: Function:
1 Master power
2
3 Set/Acc
4 Unsure but is live with ignition on and cc on
5
6 Same as 4
7 Reset/Decel
8 Unsure but with foot brake off 9.5v, and foot brake on 10.4v


Cheers

Hi Ben, had same problems with my softdash, turned out to be the ecu so i opened it up and found heaps of dry soldered joints. just went over them with my soldering iron and it hasnt missed a beat for 12 months (touch wood) worth a try mate.