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1995-2002 Range Rover P38A
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Discussion Starter #1
Has anyone opened one up to see what's going on (Hella, pre-'99)? I know that other ECUs can suffer failure due to aging capacitors. I suppose I should find a spare to see if the ECU is truly the problem, and then open up my old one. Been through the ETM tests. They seem to be getting harder to find.
 

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I have been through 3 of them in my two cars. They are very similar on the classic/disco. Its not the cap which has failed on any of mine. I did fix one by replacing a driver transistor, and one lasted a bit longer by cleaning the relay contacts.

I have no idea what really causes it. I think the steering column connections must go flaky as well. Mine sometimes will just not work and click incesantly unless turned off, maybe once a month.
 

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Which of the transistors are the "driver" transistors? Does anyone have a schematic for this? In my case, no leaks in the vacuum pipes and the ETM pointed to the cruise ECU. I replaced the 2 big electolytics (the 470u/25V and 3.3u/50V) but to no avail. My CC is very inconsistent. Every once in a while, it will work and last for maybe 5 minutes then it just quits altogether. After that, it could be months before it even works again. I thought this might be due to the electrolytics drying out but as this last test points out, that's not the case. No clicking either. Any ideas?
 

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1995-2002 Range Rover P38A
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I just replaced the ecu and the relay on my 96 rr and got bupkis. the vaccum hoses and diaphram don't look to be cracked, brittle or bad at all. The cruise control on off switch lights up but thats all i get.

at first the cruise control would just drop off and i could reset it and it would work fine for a while. but now it doesn't work at all.


any ideas?
 

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My Discovery 1 uses the same Cruise Control. I have 2 ECU's but the one never worked and the other failed a week ago.

So, I just designed a new ECU. Basically all one does is to desolder the terminal and resolder it to my new board. It will fit exactly in the original housing so it will be like plugging in an original.

With the new electronics, there is lots of space on the board so I have added 10 indicator lights so that one can for a change trouble shoot easily. It will show the state changes of all the inputs like the brakes, clutch, steering switches, if there is power to the board, output to the motor, the speed signal etc.

It also has a stationary test function where one change a jumper on the PC board and then one has a dummy speed signal pot to allows you to test the system fully while the vehicle is stationary with only ignition on.

This way, it will enable most DIY enthusiasts to get their systems working again easily. Trouble shooting will now be a real breeze.
 

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I had two intermittent ECU's. In both cases it was several bad solder joints on the PCB. Main challenge before re-soldering is cleaning off the varnish or whatever the coating is. The main problem on 1st one was dry joint on one of the small capacitors in the centre of the PCB. Eventually found it using my £20 USB Microscope. On e 2nd ECU I never found the bad joint(s), but re-soldered every joint just for good measure, and the ECU has been working ever since.

Pete
 

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Yes I found the same problem in early 2013 - quite a few dry or bad joints. I just used a small screwdriver to scrape away the coating and re-touched them. Now no problems.

Dodgy components.JPG

Rowan
 

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1995-2002 Range Rover P38A
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If it only just switches on and off (visible) and nothing happens my first check should be the clockspring cassette inside the steeringwheel.
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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If it only just switches on and off (visible) and nothing happens my first check should be the clockspring cassette inside the steeringwheel.
The GEMS vehicles are notorious for the ECU failing with dry joints - if the clockspring has failed then generally the horn/ICE controls (where fitted) also won't work - and you'll get an airbag fault on the dash as the drivers airbag connections go through it aswell. It could be that just the cruise switch wires have failed in coupler, but most of the time they all fail at the same time.
 

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1995-2002 Range Rover P38A
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RIGHT HAND SIDE OF STEERING WHEEL - take off the panel under the steering wheel and you'll see a metal canister the size of a packet of cigarettes metal/aluminium if a gems or a black plastic case if the later vesion
 

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Long since the update, but I have completed the Cruise Control in November last year and have been using it for the past few months.

I am quite experienced in PID control and this was by far the most difficult system to get working smoothly.

Permanent blank boards are made.

Check out the row of LED's. Now you can trouble shoot the thing easily as all inputs and outputs are indicated.

2017-05-17 20.02.34.jpg
 

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1995-2002 Range Rover P38A
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Long since the update, but I have completed the Cruise Control in November last year and have been using it for the past few months.

I am quite experienced in PID control and this was by far the most difficult system to get working smoothly.

Permanent blank boards are made.

Check out the row of LED's. Now you can trouble shoot the thing easily as all inputs and outputs are indicated.

View attachment 227346
VERY cool, well done! I would also have to ask... "what kind of $$ and lead-times would we be looking @?"
 

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1995-2002 Range Rover P38A
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Hey where can I get one with the leds I have the same problem, switch lights up and nothin else. All hoses new.
 

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OK, let's be honest.

There have been some legitimate arguments raised that a product like this in particular, can expose me to liabilities. I do not think it is a warning to consider lightly being in the engineering business all my life.

If any guy buys this unit from me, it malfunctions and he makes a prang, claims this unit caused it and I am getting sued, then it obviously is not what I had in mind as this is not supposed to be a high volume commercial product where one can go through the pains to get TUV approval and ISO 9000 certified for example.

Remember, that this unit depends on salvaging the exiting terminal of the old CC unit and it is not as if I have a pile of them available. This means for quick turn around time the end user in any case will have to change the terminal himself.


I have gone through a careful design process where this unit is fitted with the yellow relay which is directly electrically activated by the brake or clutch and it physically cuts the power to the vacuum pump motor through the NO contact of the relay - regardless of what the controller commands.

For example: When I began programming the unit it was obviously mad at times and when the cruise control was set it simply pulled in the throttle to the floor and did not let go. Dealing with that was easy. Simply touch the clutch or brake pedal and it will release. Another way is to press the dash switch.

Secondly, the vacuum hoses are also supposed to be routed through those same switches for an additional mechanical cut - and my vacuum pipes are not even connected.


One way to get around the liability issue above is as follows:

1. The board gets published as open source under an open hardware license. This means that I also need to publish the wiring diagrams, Gerber files and part list so that anyone who wants to can have his own blanks made and assemble it. This I support in principle in any case.

2. I (or anyone else) sells the board completed, but with the Arduino not plugged in, not programmed and without the the terminal.

3. The end user then has to salvage the terminal from his existing board and solder it in to the new unit.

4. The end user needs to upload the software to the Arduino - which is silly easy as it uses a mircro-usb plug the same as almost all cell phones. And the software is free.


What I find most awesome about my unit is that it allows those people who really want to dig their heels in to control theory, to make their own unique program. I have for example lowered the minimum activation speed from 40 to 30 km/h. I have also put in a test function where when the vehicle is stationary the vacuum pump and release valve can be activated in both directions which make testing of the motor and vacuum lines much much safer and far less frustrating that truing to find the problem at above 40 km/h where you as diver cannot observe anything.


If a user goes through these multiple steps of conscious decision and does some assembling himself, then it seems that there is enough of an argument that I as the original designer cannot be held liable if something goes wrong.

Any thoughts on the matter will be appreciated and I would like to explore it further as I am highly interested in open source hardware development - and the fact is that legally it is still not that well defined which in these days puts a damper on collaboration of innovative ideas in an world that is not so free anymore.
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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Guys, I replaced my Cruise Control ECU/Controller with one from a 99-2002 about 5 years ago NO ISSUES! Not one.. This is an easy fix, I did a post about this at the time.

Scotty
 

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1995-2002 Range Rover P38A
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Ok, so I know this is an old thread, but all my searching and googling kept leading me to this thread, so I thought I’d post my experience to help others in the same boat.
Like some of the previous posts, running through the ETM lead to the ECU being at fault. I swapped it for another and my cruise still was not working. Had previously replaced and/or tested all other components.
Since I now had two ECUs I decided to risk resoldering one of them. I bought a tub of flux and got to work. I smeared flux all over the back of the board, then melted every join. I wasn’t sure what to do with the half of the board with the varnish coating so I just kept going like it wasn’t there. I added a bit of solder to a few connections that looked a bit bare.
To be honest my ham fisted attempt looked so rough I had no expectation it would work, but I plugged it in and it works like a charm!
So anyone out there who suspects an ECU fault, have a go, you might be surprised. I am in no way anything close to an expert.
My only advice would be to grab and use some flux.

Cheers.
 
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