Xyz switch

Hi
Sorry for posting another xyz switch tale.
I have a facelift Td5 auto
I purchased the car with the m and s lights flashing.
I changed the switch and the wiring harness. The car drives fine until you either use the air con or headlights and the car will go into limp mode, turn the car off and any electrical load and it will drive fine untill either of the above are turned back on. I have now put the car into a local landy specialist who has checked the switch and wiring and confirms that both are fine. It has had a new battery in the last month and alternator last year. Although I trust the guy doing the work it doesn't seem to be getting any further with it. Has anyone had a similar experience or have any idea what it could be.
Regards
Dsve

My first guess is bad earth somewhere.

Col

Yeah, I was thinking along those lines. I have cleaned and checked the ones around the battery and air cleaner so far.

Check ALL the grounding/earth points especially in the engine bay, at the firewall and both RH & LH 'A' posts near the front doors.

Thanks for the replies and image for the earth's. Spoke to the garage today and he thinks it's the gearbox ? So will be getting the car back from him next week. I don't believe it's the box it certainty hasn't shown up on nanocom when tested. Also spoke to Ashcroft and he'd never heard of this particular problem.. Bit peed. Off with the garage they have had the car two weeks and Ian meant to be going to Cornwall on the 17th. Will get it back and try and find the earth's

It's possible to be a voltage drop when aircon is switched on cos it has quite serious load so watch the battery voltage then and if it drops below 12V the problem is on the charging path even if the alternator was changed

Thanks for the reply. I did wonder whether the alternator was playing about under load. I am going to get the car Monday and see if my local garage ( should have gone there first ) can fit me in. Another week has gone by and he hasn't touched the car. Will post up the ( hopefully ) positive results!!

Davrav said:

Thanks for the reply. I did wonder whether the alternator was playing about under load. I am going to get the car Monday and see if my local garage ( should have gone there first ) can fit me in. Another week has gone by and he hasn't touched the car. Will post up the ( hopefully ) positive results!!

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As soon as they stop touching the car it is a very bad sign as it means they haven't a clue so give up and start working on other peeps cars they know they can fix. Once happened to us for 2 months when a garage couldn't tune in fly-by-wire electronic diesel injection on an admitteldy rare car. In the end we they had to get it to a specialist to fix.

Yep you are Correct he definitely lost interest. Got the car back today absolutely covered in muck and dust/ dirt, not overalls happy as it went in nice and clean.
As soon as I drove off the flashing green light emerged and I know he took the switch and obviously hasn’t aligned it properly, yes I know I should have turned back to get him to do it but I am so fed up I just thought I’ll do it myself.
The battery was low so have put that on charge. not a great experience and still not fixed

Davrav said:

Yep you are Correct he definitely lost interest. Got the car back today absolutely covered in muck and dust/ dirt, not overalls happy as it went in nice and clean.
As soon as I drove off the flashing green light emerged and I know he took the switch and obviously hasn’t aligned it properly, yes I know I should have turned back to get him to do it but I am so fed up I just thought I’ll do it myself.
The battery was low so have put that on charge. not a great experience and still not fixed

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Such a shame. hope you didn't pay him. If he argued I'd say "fix it then I'll pay you"

Davrav said:

The battery was low so have put that on charge. not a great experience and still not fixed

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Then start and investigate on the charging path.

The charging system appears to be working on. I think it's the fact the car has not been used for 3 weeks.
Also just noticed today the plug for the air con compressor was not plugged in and the shroud has disappeared from the top of the rad for the fan. I did pay him for his Time rightly or wrongly £100.00. but obviously didn't realise it had the issues it did. Going to ring him later as I have already sent him a text with no answer.

Davrav said:

The charging system appears to be working on.

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Did you watch the voltage while the symptom occurs ?

For about £10 you can get a usb/ voltage meter to put in the cigar lighter. Then you can keep your eye on the battery, prior to starting, and the alternator as you are driving. What voltages are you seeing... The P38 gearbox HP24) will have a wobbly if it sees a low voltage - yours may be doing the same. Worth looking at voltage drops to see if there is a wiring issue - but I wonder if the alternator is doing its job - may just need a replacement VR. Worth also getting a clamp meter, to work out how much Current is actually getting drawn from the battery (hopefully none)

Davrav said:

The charging system appears to be working on. I think it's the fact the car has not been used for 3 weeks.
Also just noticed today the plug for the air con compressor was not plugged in and the shroud has disappeared from the top of the rad for the fan. I did pay him for his Time rightly or wrongly £100.00. but obviously didn't realise it had the issues it did. Going to ring him later as I have already sent him a text with no answer.

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Plug left off, mechanic's fault?
Rad/fan shroud missing, mechanic's fault/
Won't answer texts? Dickhead.
He is avoiding the issue and working in a slapdash manner. Glad you only paid him £100. Fairly cheap to learn he is a Dhead!

Does the MIL (engine check light) illuminate when the M&S lights flash? If no then it is definitely a voltage issue. There are many faults that will throw up the M&S lights, but only one that will not also light the MIL - battery voltage less than 9V with the engine running. If the battery was really down to 9V then no way would it start the engine and the alternator should be pushing out way more than this, so normally this is a a loose battery terminal or an intermittent earth connection rather than a dead battery.
If the MIL is on, then you need the code reading to find out why as this could be for anything from a slipping torque converter to an invalid engine speed feed.

No the mil light doesn't come on. I have cleaned up some more earth's.
I do think it is a voltage issue. I have purchased a plug in voltmeter to check the voltage when driving but at the moment I am having trouble adjusting the xyz switch just can't seem to get it correct. Late now will have another try tomorrow

If the MIL is not on then this is definitely a voltage issue. As SF has pointed out, you need to check the charging system - maybe a faulty voltage regulator?

Thanks turns out you were on the money...
Well after a lot of time and effort I went back to https://www.discovery2parts.com/. And I can't thank the guys enough. It was the alternator (which was new prior to my ownership) that was at fault, as soon as it was unplugged the car drove perfectly, prior to that that it was now in limp mode all of the time as opposed to some of the time when under load.
A new denso one shall be ordered tomorrow. Happy to say the least.

Glad to hear you tracked down the fault. Now all you need to is swap in the new alternator.
You will need to remove the viscous cooling fan, rather than trying to brace it with something and then smack the nut with a chisel, my advice is to invest in one of the spanner sets designed for this purpose - it will not be the only time you need it....
I have the one from Flatdog and it works well.
Getting the old alternator out is much easier if you remove the hose from the intercooler to the EGR valve or inlet manifold.