I have never had an older rover do dii range river that put out more than 12.5v..

Well my new disco is only putting out 11.5.. Sure it runs, should I fix it? Or if it ain't broke don't fix it?

Also anyway of curing this without replacing whole alternator?

 

If the battery is sort of toasted and bad, then you will only see 11.5 volts.
If the alternator is really really hot, then it is pumping 100 amps or so at the battery
but the battery is bad and is turning all the current into heat.

Go to Walmart. $110 get a new battery.

If your alternator never heats up - then it is putting out nothing and is bad.

What I would do -

Put a battery charger on the Rover all night.
The current should start out high - 8 to 12 amps.
And, it should creep down to 4 amps in the morning - if the battery is good and working correctly..

Then you can see if you have 12.5 volts on the battery.

13.8 volts is the usual battery voltage when the Rover is running.

 

First verify your test meter is working on another vehicle.

Parts stores usually test battery for free.

At home, here is one way.

1. Measure battery volts with truck off, nothing on. May be 12.6 volts.

2. Switch on head lights. Volts should drop a fraction, but not down to 10 or 11 volts. A quick drop indicates a weak battery (dead cell).

3. Crank truck up, and let it idle, nothing else on, keep that dang sub woofer switched off. Volts should come up to 13.4 to 14.4 (with lights on, without maybe 13.8)

3. Switch on everything else you can. Volts will drop a little with larger items, but with all on should be at 13.2 or above. An alternator with problems (regulator or diodes) will put out no amps, and you won't be running in a few hours, or it will put out like 1/3 to 2/3 of the regular amps. So you can drive in the daytime OK, but at night with AC and wipers and stereo on, along with lights, you can draw more than the weak alternator can supply.

If all you are getting at battery is a real 11.5 you are not charging and you will be found on the side of the road.

 

Rovers need between 13.6 and 14.4 volts or the ECU won't run right.

 

have the battery load tested #1, make sure it is fully charged #2, check ground connection #3, replace as needed