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Land Rover Disco 3 voltage regulator levels

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 7812 regulator in the DVD player power lead!

Reply to
Ron Lowe
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That's definitely pushing the absolute upper limit that you'd expect to see, go & ask your dealer.

Reply to
Duncan Wood

That is too high. I wonder how high the voltage gets when you are under way?

The LR system sounds complex but it possibly samples the system voltage from one point only, and if the cabling there is deteriorated, that would be the problem. Or maybe one of the sensors, like the ambient temperature sensor, is faulty and causing the system to overcompensate.

Hope your dealer doesn't smile and say, Yes, they all do that, Sir.

Reply to
Mark W

I agree that voltage is too high.

LR use a similar system to what Ford invented for the Focus (and now is present on most of their cars) It's called smart charge and the ECU controls the alternator field excitation. The idea is that it works in conjunction with a Calcium battery.

You do have the proper calcium batt fitted don't you? If not this will screw up the charging volts.

Anyway, the idea is that with a cold battery, the alterntor can pump in the juice at a much higher rate, so the ECU alters things accordingly via the ambient air temp sensor, and the battery compartment sensor.

If it is accessible, you can remove the smart-charge control multiplug from the rear of the alternator and it will then defailt to charging at a fixed

14v.

I would say you have a problem with what the ecu is seeing with regard to system voltage or air / battery temp.

Tim.

Reply to
Tim..

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