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Discussion Starter #1
After bragging to a friend that the P38 is now 20 years old and after 11 years of ownership it never gives any problems (big mistake:naughty:) the old girl hit me with a handful of headaches all at once.
First the cruise control just stopped working. The switch lights up but nothing happens when I press the button on the steering wheel. I spent a cold afternoon looking for the cruise control module only to realise that it doesn't have one because it's a diesel. I couldn't find any vacuum pipes either but not sure if there is any vacuum system with this set up.

The other problems aren't related and are easily sorted but I'd appreciate any ideas, suggestions or general comments on cruise control.

Many thanks

Pete
 

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There is a control module:
Z249 Cruise Control Converter/Inverter Module
It supplies the signal to the engine ECU.

Looks like a black tall relay. Snapped a picture from my car just now. On LHD vehicle it's located beneath the steering wheel to the left. Sorry for the poor quality.
IMG-3169.JPG
 

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Discussion Starter #4
Thanks for the replies. My car is RHD and I can't see the module where you described but on the other side Kretslopp so maybe it's on the same side as yours behind the glove box.
Sadly I'm a fair weather Mechanic now so when it fairs up a bit I'll have another go at it.
Thanks again
 

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Engine ECU controls the cruise control on the diesel vehicles.

There should be the inverter module in the dash somewhere - on a RHD it *should* be on the RH side of the steering column, and accessible by removing the knee panel and the binnacle.

Out of interest, what are the other faults that have recently show up?
 

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Yeah it would be odd if it were on the opposite side of the steering wheel when it is wired to the rotary coupler in the steering column.
This is what it says in rave:


"behind RH side of fascia right of steering column"


Sounds like the exact opposite of the LHD position.
 

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Discussion Starter #7
marty_nz; Out of interest said:
Years ago I had a problem with hot starting and I fitted a kit which allows the glowplugs to come on when hot. It has worked fine for about 5 years but suddenly stopped. Interestingly it is spliced into the engine ECU wiring so it is possible that there is a link. Then I started getting a low brake fluid message when it isn't ......low that is. Foolishly we discussed the possibility of selling the old girl within earshot and I've owned the car long enough now to know that she's sulking:crybaby2:

Thanks for the info. I'll have another look tomorrow and report back.
 

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Discussion Starter #8
Had another look today and found the elusive CC switch converter. Right where everyone said it was. Unfortunately the test procedure in my copy of Rave is for the V8 model, not the Diesel . Anyway I did a few tests and found that:
Terminal 8 is live when the dash switch is on.
5 gives 30 Ohms when cruise button on steering wheel is pressed.
4 gives 30 Ohms when Resume button is pressed
1 gives 5v +ve with ign on
and 6 gives 1.3 K Ohms in N and P and 2.9 in any gear.
I wasn't able to test the brake switches because I couldn't find where they feed to. (any ideas)
Might take a punt on a switch converter off Ebay.:shhh:
I'll be back.
 

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Where is that test procedure located in rave?

I'd disconnect the connector on the inverter module and measure terminal 5 and 6 against ground. Those switches in the steering wheel connects directly to ground when pressed and there should be 0,5ohm when pressed.
If not, the buttons or the rotary coupler or ground itself is bad.
 

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Discussion Starter #10
Where is that test procedure located in rave?
Section B5 11 to 23. I think it's pages 70 to 84. but as I said it's for the petrol model.

I find the wiring diagrams a bit hard to follow but the brake switches seem to go straight to the ECM so that's where I'll start when time permits.
I gave the steering wheel a vigorous lock to lock when testing the switches and the reading was nice and steady.
My Wife has never once used the cruise control and I use it once in a blue moon so I'm sure that life would be possible without it , it's just niggling that stuff like that decides to stop working.
Life as we know it has almost ground to a halt because we had 2" of snow overnight so tomorrow the Rangie must be pressed back into service.:thumb: Cruise or no cruise
 

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Ok, I found that section now.
In the version of rave I have there is fault finding process for diesel model also.

Test E and F is related to diesel model.
What I wrote about terminal 5 and 6 on the inverter module is actually the last part of test F. :)

You write that the reading was nice and steady. Do you mean 30ohms as you wrote earlier? Between terminal 5 to ground and then 6 to ground, with no voltage and connector disconnected?

If that's the case you definitely have a problem there.
 

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Discussion Starter #12
Thanks Kretslopp
Interestingly with connector disconnected, terminals 4 and 5 to earth both read 30 0hms with respective steering wheel buttons pressed. Terminal 6 is linked to the gear change.
I'm wondering now how accurate my multimeter is and I'll get some better readings with my more reliable meter as soon as I get a chance.
Thanks
 

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Discussion Starter #13
Cruise Update
Found your test procedure Kretslopp and with a decent multi tester got 3 ohms between the steering wheel switches and earth. Interestingly terminal 4 on the converter/inverter goes to the res switch on the steering wheel and the manual test procedure states that it should be terminal 6 ??? My car doesn't have the decel function so maybe that's the difference.
Anyway everything else tested out as it should and I took a chance on a £10 converter / inverter module off Ebay and it's all working fine again:D Happy days.........till the next time.
Thanks again to all for help and ideas
Pete
 

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Bought my diesel about a month ago drove it back from Southampton uk to Wales trying the cruise and in usual p38 style
nothing, but today works perfectly, so will be looking for bad or dirty connections.
 
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