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16th April 2024, 07:12 | #11 |
Gets stuck in
Rover 75 Connoisseur 2.5 V6 auto Join Date: Jan 2008
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I've had KV6's since 2007, and always done my own maintenance.
I agree that the brake pedal switch is the most likely cause, everyone seems to mention that. However, on occasions I have suffered a different symptom. On the bulkhead, offside of the engine, you will find the vacuum pump. The hose from the throttle body diaphragm should terminate on this; I have had it loose or dropped off on 2-3 occasions. |
16th April 2024, 12:52 | #12 | |
This is my second home
Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009
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Quote:
Well I thought it would take longer to trace and check the cables out than it would to just replace the coupler, so seeing as I had a spare one from a scrapper I tried it and that cured the fault. Splitting the coupler and inspecting the ribbon cable I found a split that had started to run across it, so if your radio buttons aren't working as well it may well be that the ribbon cable has started to go south. |
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16th April 2024, 12:55 | #13 | |
This is my second home
Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009
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16th April 2024, 13:02 | #14 | |
Gets stuck in
Rover 75 Tourer Join Date: Mar 2022
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16th April 2024, 17:04 | #15 |
This is my second home
Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009
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Yep that sounds like a good plan. 👍
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16th April 2024, 17:15 | #16 |
Gets stuck in
Rover 75 Tourer Join Date: Mar 2022
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I've just been out experimenting.
I disconnected the plug from the rotary coupler and hot wired a switch across the light green/red and the black wires. It still doesn't work, so the fault is obviously elsewhere. I didn't realise when I was checking at Gaydon, but there are actually two fuses for cruise control. I've checked the other one and that is also good. A couple of things are confusing me. The wiring schematic shows a cruise control ECU for the petrol model and a cruise control relay for diesels. Mine is a diesel. I can find no mention of this relay - R142 - or its location. The schematic also shows a feed from fuse 4 in the engine bay fuse box to the CC relay. Last but not least, the schematic for the rotary coupler would appear to have an error. I would expect the common side of the two cruise switches to be connected to ground, along with the horn buttons, but the schematic shows them connected to the wrong side of the horn buttons. So, does anyone know where the CC relay is located? That might be my next step, along with checking fuse 4 in the engine bay fuse box. |
16th April 2024, 21:09 | #17 | ||
Doesn't do things by halves
Rover 75 2.5 Connoisseur Auto (1999) Dealer launch model. Join Date: Mar 2007
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Simon
__________________
"Whatever is rightly done, however humble, is noble." Sir Henry Royce. |
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27th May 2024, 20:33 | #18 |
Gets stuck in
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UPDATE: Problem Solved
OK, cruise control is now working again and I've made some interesting discoveries along the way.
At the Midlands nano meet on Saturday, Duncan ran some T4 diagnostics and we found that that the brake light switch was fully functional, the 'resume' switch was OK, but it wasn't seeing the 'set' switch. I thought I had eliminated the 'set' switch and the rotary coupler by rigging a temporary switch to the rotary coupler connector, between the 'set' signal wire and ground. I rather foolishly assumed that the common side of the two CC switches went to ground. This is not actually the case, and there isn't actually an error in the RAVE wiring diagram, as previously thought. What we have on the common side of the CC switches is a 12v feed. Not just any 12v feed, but one which comes from the ground side of the horn relay coil. Someone at MGR, having realised that they didn't have a spare pin to provide a dedicated 12v feed, rather cunningly decided to take it from the ground side of the horn relay. This obviously works fine, unless you try to sound the horn and set or resume cruise at the same time. This is why the CC switches are connected to the 'wrong' side of the horn switches. ...and you can see from the following photo that the CC switches have yellow and blue wires for the signal and a purple wire connected to the horn circuit, rather than a black wire to ground. Getting back to my fault, having identified that the system was not seeing the 'set' switch, I did a continuity check on the wiring between the coupler and the cruise interface/ECU, which was all good. I also did a continuity check from the rotary coupler plug to check the switch/coupler, which was open circuit. I do have a spare rotary coupler, so I tested it and found that it was good apart from one of the audio wires being open-circuit. My audio buttons didn't work anyway, so I decided to fit it. Having removed the existing rotary coupler, I found that one audio wire and one CC wire were open-circuit, so I fitted the spare coupler and I now have working cruise control. All I need to do now is find a good rotary coupler and then I will have working audio buttons, too. Last edited by daveo138; 29th May 2024 at 06:57.. Reason: Added ‘coil’ to horn relay. |
1st June 2024, 17:17 | #19 | |
Gets stuck in
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It turned out to be the coupler, after all. See above. I've just dismantled the old one and can see no signs of any damage, at all. It's the two centre conductors of the six that have failed. |
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1st June 2024, 23:09 | #20 |
This is my second home
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Good to get a result and put it to bed Dave. 👍
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