Cruise Control problem...? - Land Rovers Only

heiff · 08-12-2006, 06:44 PM

I decided to tackle the cruise control on my 93 RRC. It hasn't ever worked since I've owned the car.

vacuum lines = ok
fuses = ok
dash switch = ok
power reaching cruise ecu on pin 10 = yes
power reaching vacuum pump from pin 1 = no

Power is going into the ECU, but isn't coming out where it's supposed to (in this case, pin 1, which powers the vacuum pump). Are there any external components of the system that inhibit voltage being supplied to pin 1? The wiring diagram and circuit description don't indicate that, so the alternative explanation is that I have a bad ECU. I'm willing to accept that - I just want to make certain that the ECU really IS bad before I dash off and try to find another...

If anyone has anything to share, your thoughts would be most appreciated!

heiff · 08-17-2006, 06:18 PM

Cruise control now works! The real culprit was simply the cruise cassette. I put too much faith in the ETM. Both the circuit description and the tests in the 1993/94 ETM refer to a previous version of the cruise system - not what's actually installed in the vehicle. The wiring diagram, however, is correct.

At any rate, what's important is that for 93/94 RRCs, neither voltage (via pin 1 of the ECU) nor ground are supplied to the vacuum pump unless the cruise switch is on, the vehicle is in motion, and the set/accel button is depressed.

glenncof · 08-30-2006, 02:50 PM

For others looking at Cruise Control problem.

My 1991 RR had a leak in the vacuum unit that pulls on the throttle.

Another thing to consider was the vacuum release valve on the foot brake.

deadboy1977 · 10-16-2006, 01:55 PM

I have a 95RRCLWB with no cruise
The dash switch illuminates
When I travel down the road and activate the cruise from the steering wheel swich, i hear a relay latch (in the ECU?) under the glovebox, but it does not catch. I would assume that this suggests that I have a good steering wheel switch, good spiral cassette and good ECU (i had a spare ECU, tried that and did nothing). all vac hoses were repladed. the vacuum unit by the throtle cable - i sucked on it with a hose and it held...........what should i try next?

deadboy1977 · 10-19-2006, 06:26 AM

anyone? Is there a vacuum diaphragm by the brake pedal? I see a vac line going thru firewall, where does that go?

sven · 10-19-2006, 07:03 AM

Quote:

Originally Posted by deadboy1977

anyone? Is there a vacuum diaphragm by the brake pedal? I see a vac line going thru firewall, where does that go?

To the brake pedal switch..it cuts off the vacuum when you hit the brakes.

08-12-2006, 06:44 PM	#1 (permalink)
heiff 1993 Range Rover County LWB Join Date: Mar 2006 Location: Seattle, Washington Posts: 18 Gallery: 0	Cruise Control problem...? I decided to tackle the cruise control on my 93 RRC. It hasn't ever worked since I've owned the car. vacuum lines = ok fuses = ok dash switch = ok power reaching cruise ecu on pin 10 = yes power reaching vacuum pump from pin 1 = no Power is going into the ECU, but isn't coming out where it's supposed to (in this case, pin 1, which powers the vacuum pump). Are there any external components of the system that inhibit voltage being supplied to pin 1? The wiring diagram and circuit description don't indicate that, so the alternative explanation is that I have a bad ECU. I'm willing to accept that - I just want to make certain that the ECU really IS bad before I dash off and try to find another... If anyone has anything to share, your thoughts would be most appreciated! __________________ - Ian 1993 Range Rover County LWB / 1996 Rover Mini SPi / 1965 MG 1100

08-17-2006, 06:18 PM	#2 (permalink)
heiff 1993 Range Rover County LWB Join Date: Mar 2006 Location: Seattle, Washington Posts: 18 Gallery: 0	Cruise control now works! The real culprit was simply the cruise cassette. I put too much faith in the ETM. Both the circuit description and the tests in the 1993/94 ETM refer to a previous version of the cruise system - not what's actually installed in the vehicle. The wiring diagram, however, is correct. At any rate, what's important is that for 93/94 RRCs, neither voltage (via pin 1 of the ECU) nor ground are supplied to the vacuum pump unless the cruise switch is on, the vehicle is in motion, and the set/accel button is depressed. __________________ - Ian 1993 Range Rover County LWB / 1996 Rover Mini SPi / 1965 MG 1100

10-16-2006, 01:55 PM	#4 (permalink)
deadboy1977 Senior Member Join Date: Mar 2006 Posts: 112 Gallery: 0	95 RRC cruise I have a 95RRCLWB with no cruise The dash switch illuminates When I travel down the road and activate the cruise from the steering wheel swich, i hear a relay latch (in the ECU?) under the glovebox, but it does not catch. I would assume that this suggests that I have a good steering wheel switch, good spiral cassette and good ECU (i had a spare ECU, tried that and did nothing). all vac hoses were repladed. the vacuum unit by the throtle cable - i sucked on it with a hose and it held...........what should i try next?

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08-30-2006, 02:50 PM	#3 (permalink)
glenncof Member Join Date: Sep 2004 Posts: 95 Gallery: 0	For others looking at Cruise Control problem. My 1991 RR had a leak in the vacuum unit that pulls on the throttle. Another thing to consider was the vacuum release valve on the foot brake.

10-19-2006, 06:26 AM	#5 (permalink)
deadboy1977 Senior Member Join Date: Mar 2006 Posts: 112 Gallery: 0	anyone? Is there a vacuum diaphragm by the brake pedal? I see a vac line going thru firewall, where does that go?

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