Land Rover Disco 3 voltage regulator levels

Ron Lowe · 2009-02-09T21:40:30+00:00

Hi, all.I have a Land Rover Discovery 3 here ( still in warranty ).The vehicle has a voracious appetite for light bulbs: I'm replacing tail / brake lamps every couple of weeks, and the same with headlamps. And at around a tenner a pop for the headlamps, I'm getting a bit fed up.Also, the kid's DVD players ( after-market ) in the back seats have started shutting down, usually when I start the engine.Fault-finding the DVD players, I was checking for the presence of 12v at the power cable.I found it to be 15.6v with the engine running.IMHO, that's too high, and possibly the cause of the lamp problem.Bench testing the DVD players shows that they indeed shut down at around 15.5 v ( protection, I guess. )What is reasonable maximum voltage on a vehicle 12v system with the engine running?I'd guess around 14v.Googling this, I have seen people saying the disco uses some fancy automatic system to optimise the charge voltage which takes into account all sorts of things including vehicle electrical load at the time, and temperature ( the battery is apparently temperature sensitive ), and possibly phases of the moon.. This can apparently cause the charge voltage to vary up to 15.5v, I've read. ( It's -9 degrees here at the moment, and the vehicle electrics are often well loaded with heated windows and seats, wipers, fan blowers etc. )Am I seeing a fault ( voltage regulator on the alternator ), or is this just within normal tollerances with these vehicles?Is it reasonable for the thing to run at 15.5v, and chew up headlamps?I don't think it is.I'm looking for some opinions before I need to argue with Mr. Land Rover for a warranty claim.Otherwise, I need to put a 7912 regulator in the DVD player power lead!

Feb 09, 2009 46 Replies

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Andy Champ 17 years ago

I'll give you the horsebox, but a dinghy is fine behind a Mini. I know, I've done it. And I mean a real Mini, not the modern BMW thing.

I don't reckon a Dart cat (130Kg) or a Laser (59Kg) even with another hundred or so for the trailer, needs 4wd.

Ron's snow is a real reason for having one. He seems to be one of the few people with a proper reason.

Ron,

I suggest you rent a decent modern road car one day for the Shropshire trip, just to see the difference. Preferably just so you can do a (practice) emergency stop on a wet road.

Andy

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<me9 17 years ago

I had that for several years on my Nissan Primera. The battery was tested as in spec but only just. Eventually I changed the battery. No bulb failures in the following two years.

It could also be poor connections to the battery (or earth straps).

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<me9 17 years ago

Having driven a range of rangerovers/landrovers/discos over the last 30 years for work I'd agree with that. Ice/snow and mud they were unsurpassable, but for open road driving the handling was suboptimum due to the suspension being more suited for off/poor road conditions. I always found that the brakes pulled to the left if the engine was revving, and were generally less effective than in a saloon/estate car.

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The Natural Philosopher 17 years ago

Exactly.

It cost about 500 a year to have a 4WD on the road even if it only turns a wheel on the few days with snow.

So if you need one, you have to use it.

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Huge 17 years ago

That's really big of you.

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Steve Firth 17 years ago

I think I'd prefer the boat + trailer if it's still on offer.

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Huge 17 years ago

*applause*

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