Intermittent 'Alternator Fault', 'Gearbox Fault', no rev counter.

Hi Guys,

I have used the search to try and find a solution to this, to no avail, so I thought I would throw it out there for a few ideas.

About a week ago, my beloved Range Rover 4.6 HSE 1995 kindly informed me that she had an "Alternator Fault" and a "Gearbox Fault" and the rev counter stopped working and the gearbox went into limp home mode.

Well, I limped to where I was going and switched off and when I got back to the car she was working fine again.

Next day, same symptoms and she stayed in 'limp home' all day.

Next day, she went all intermittent on me; sometimes okay, sometimes not, even starting a journey in limp home and then coming all normal on me half way through the journey (these are just short jaunts around town).

So, she has a new battery, less than two months old, alternator is charging nicely at 13.8volts (even with the fault). Fortunately I have an identical car of the same year parked next to her on the drive so I swopped the alternator, the fuse box, the ABS ECU, (someone suggested it) removed all the connectors on the BECM and cleaned them, but intermittent fault still there.

I should mention that I do not have access to Testbook or other diagnostics as the nearest is about 180 miles away. Also, the climate here is a bit extreme (35c for the past week or so for example) so the engine bay is always mega, mega hot!

Any suggestions gratefully accepted.

13.8v is too low...expect Alternator output at 2000rpm is around the 14.2-14.4V mark....

The Gearbox Fault I suspect is in sympathy to low volts at the ECUs

May be worth checking the earth straps and and cleaning the connections.

Sometimes they can corrode inside any insulated covering.

Pete

99% sure it will be the crank sensor.........i left mine unpluged after cleaning it and have the same msg's on the dash as you........

13.8 volts is too low, may indicate a diode failure in the alternator.

rousecapri said:

99% sure it will be the crank sensor.........i left mine unpluged after cleaning it and have the same msg's on the dash as you........

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Not 100% sure that the Crank Sensor will give those warnings...sure as heck the Engine won't start with it unplugged mind!!

Datatek said:

13.8 volts is too low, may indicate a diode failure in the alternator.

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Checked mine yesterday and I got 13.8 at tick over. Went to 14.3 at higher revs.

Yes I got all those symptoms did all the earths even changed the fuze box..Turned out to be a loose crank sensor only 2mm movement...

sas1810 said:

Checked mine yesterday and I got 13.8 at tick over. Went to 14.3 at higher revs.

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That's correct, should be 14.2 +/- 0.2 volts at 2K rpm.

Datatek said:

That's correct, should be 14.2 +/- 0.2 volts at 2K rpm.

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Something working correctly then

sas1810 said:

Something working correctly then

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Probably not for long being a P38

After doing my ignition coils recently, I forgot to plug the grey connector back into the valve sitting to the rear of the inlet manifold, when I started it up the rev counter wasn't working and I got "alternator fault" appear on the dashboard. Mine's a Thor though. I have no idea how that connector could be in anyway related to the faults described! - Weird.

mmm, thanks for all the input. Mysteriously the fault has now gone away - she has now gone on to frying the aircon blower relays and occasionally refusing to run the aircon compressor at all! If the same fault comes back I will look at the crank sensor as that seems to be the next suspect.

Changing the engine bay fusebox fixed it no problem! Now it need to look at ways to ventilate the fusebox and protect it from too much heat.

Baloney999 said:

Changing the engine bay fusebox fixed it no problem! Now it need to look at ways to ventilate the fusebox and protect it from too much heat.

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External heat is not the problem, water and bad contacts cause the failures.

Problem came back weird stuff happening with the BECM now too - like my memory seat setting pushing me into the steering wheel; might change her name to Christine a la Stephen King! I keep trying this n that to fix it but no luck yet - any more suggestions most welcome.

I got gearbox fault once .limp mode ect ,found the prob when fuse 14 blew ,for the drivers seat.It got moved by mot guy and it removed a small bit of cable caseing,sparked on metal frame o seat .(Might be why you seat moved ) fixed wi a bit o tape ....Thats my 2 pence worth ....

I replaced the battery under warranty and the problems seem to have gone away. On the heat/ ventilation issue, I removed the felt bonnet lining a while ago due to it gradually disintegrating and I noticed that the vertical sides of the bonnet have large square holes. At the windscreen end of the sides behind the hinges there is a felt/rubber pad covering a similar hole. If you remove this, you can get a through flow of air into the void between the front door and the wing which vents out of the gap between the door and the wing. I reckon this will help to vent the bonnet air space without cutting vents into the wing or bonnet.

What's the alternator reading on the identical car?

I cannot remember exactly, I think they were both about 13.8+ on tickover. It was a borrowed voltmeter and I have given it back now.