THE ROVER SD1 FORUM

briggy2007 · SD1 User Joined: 01 May 2007 Posts: 19

Evening all, I have been trying to get the cruise control working tonight. It is the hella system and I am following Ramons guide.

For the vacuum unit to work, does it need 12 v via both the green and slate wires? I only get 1.3V from ECU pin 4 (the green wire) I cannot get the vacuum control unit to do anything but I think,even when stationary, with the cruise turned on, I thought I should still get something from the vacuum unit. I am trying to narrow down if it is the ECU or the vacuum unit which is duff - or something else wrong!

Any advice would help! Thanks!

ramon alban · Posted: Tue Nov 27, 2007 12:49 am Post subject: Re: Cruise Control ECU Voltage

briggy2007 wrote:

For the vacuum unit to work, does it need 12 v via both the green and slate wires? I only get 1.3V from ECU pin 4 (the green wire) I cannot get the vacuum control unit to do anything but I think,even when stationary, with the cruise turned on, I thought I should still get something from the vacuum unit. I am trying to narrow down if it is the ECU or the vacuum unit which is duff - or something else wrong!

Any advice would help! Thanks!

Briggsy,

I dont think the elecronics system can operate the vacuum system below 23mph.

You may get 12v at the slate wire via the overspeed relay by I dont think that the green wire will be grounded by the ECU.

The vacuum system can be tested with the engine not running.

Disconnect the vacuum contol unit from the system, ping off the cover and apply 12 volts between Slate (+) (15A) and Green (P) to see if the vacuum pump runs and if the system will work along with the dump switch and actuator.

The vacuum relay inside the control unit can be actuated by finger pressure.

After doing the above to establish the vacuum system was OK and strong enough for the TP, I pretested my installation with the car on jacks and the rear wheels being "driven" at more than the minimum speed to see if all the controls worked. They did, so I then road tested it.

However I did have the advantage having driven two cars with this system and knowing that the transplanted system was 100% ok before it was stripped from the donor car.

_________________
Ramon

briggy2007 · SD1 User Joined: 01 May 2007 Posts: 19

Ramon,

Looking at the diagrams in the operation, test and instruction manual on page 8, I was thinking that when ever cruise was "on" then the vacuum pump is running, the cruise doesnt engage because the vent valve in the control unit is open to vent -i.e. the yellow wire has no voltage on it and it is the yellow wire that gets 12 v when the the 23mph is reached. Anyway, I will try and hotwire it tomorrow as you describe to see if the vacuum pump works.

Thanks

Chris

ramon alban · Posted: Tue Nov 27, 2007 6:24 pm Post subject:

briggy2007 wrote:

Ramon,

Looking at the diagrams in the operation, test and instruction manual on page 8, I was thinking that when ever cruise was "on" then the vacuum pump is running, the cruise doesnt engage because the vent valve in the control unit is open to vent -i.e. the yellow wire has no voltage on it and it is the yellow wire that gets 12 v when the the 23mph is reached. Anyway, I will try and hotwire it tomorrow as you describe to see if the vacuum pump works.

Chris
You may well be right, I am not familiar with the innards of the ECU as I never had cause to investigate a failure.

Just to be sure we are on the same wavelength. The red line on the attached diagram shows the elecrical path via the Overspeed relay that must be engaged by the engine running.

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_________________
Ramon

briggy2007 · SD1 User Joined: 01 May 2007 Posts: 19

Ramon,

Yep, we are on the same wave lenght but when the engine is running, I measure 12V measured between earth and the slate wire at the vacuum unit connetction, but measure 12V across the vacuum unit and 0v between pin 4 on the ECU and earth.

Anyway, I cant check anymore as the Rover broke down on the way to work this morning. sulk sulk, one minute fine, the next dead. It wouldn't start again but I had fuel pressure, the injectors were firing and the spark was nice and healthy but it just kept on cutting out as soon as it fired. Anyway I had an important meeting this morning so I had to just ring the RAC and get it to the garage next to work and leave it. They are busy at the moment so I probably wont hear anything for a few days. For all its faults I love the car and could always say "it gets me to work and back" but obviously spoke too soon! Anyway, plan now is to go buy a banger tomorrow and use that and when the rover is running, get an MOT test and see what needs doing to it.

Hopefully its nothing major though and I can be happy again!

Chris

ramon alban · Posted: Wed Nov 28, 2007 1:30 am Post subject:

The pump may well be running, but for the vacuum to be felt in the system you must actuate the vacuum relay by hand as mentioned.

Pop the top off the control unit and try it.

_________________
Ramon