Hi all - hope someone can help me out here - I've just bought my first Land Rover - a 1995 Discovery - Yeah!

It has this problem where the lights (interior & headlamps) pulse significantly and seem to follow the engine pulsing. So, it only happens when the car is idilng, or low RPMs (not positive about this part, but I seem to remember thats the case)

My battery died, and the mechanic who replaced it said he could see the voltage at the battery pulsing up & down - I think it went from just over 12 to as high as 14. The pulses he could see on the multimeter matched the pulses of the lights. The mechanic said long-term this would over charge, and ruin the battery.

But, I've also been told that the Discovery ECU requires 13.8 volts...
So, several questions here - if the 13.8 volts are seen at the battery, is that necessarily a bad thing?

Any ideas on what could be causing the pulsing? The alternator has been replaced only about a year ago, but I guess it could be bad...Not sure what the reason for previous replacement was.

Lastly, if the 13.8 is seen at the battery, is that necessarily the precise voltage seen by the ECU? And, if its pulsing, is that going to damage my ECU? Or, could the voltage fluctuations even be causing the changes in engine idling? (as opposed to being the symptom ?)

Any help greatly appreciated! I'm in Australia BTW. Thanks! -Chris

 

It looks like you are going to buy a new alternator.
There should not be a wide swing in voltage like you have.