Technical alternator FUBARED??

[nikkiy9]

last few days i've had to bump start the car, got a multimeter on it last night and FULLY loaded (everything on :- radio, fogs, lights, heater) the voltage was as low as 12.8v




now, due to the light upgrades i'm going to be doing i will need a bigger charge, so would i be fine fitting a diesel alternator and battery or should i just get a new alternator?

 

[Brendan W]

Clean up all earths especially the strap to the gearbox and check for corrosion at the battery end of the earths as well. Bad earths drop the voltage. Check the voltage between the block and the battery earth post should be effectively zilch and for good measure check the voltage between the coolant and the -ve post with the motor running - if more than 500 mV you've got strays going back through the coolant and it needs changing. Check the battery voltage at no load , should be about the 14+ mark with the motor running. Lastly how old is the battery?

 

[Brendan W]

Now that I've actually read your post 12.8 doesn't sound too bad depending on what loads you got and presuming you did this at idle. Load tests will drop a healthy battery to around the 9V mark depending on temperature. Try all those loads with the motor stopped and you'll soon see what the alternator is not doing.

 

[nikkiy9]

The reason I fully loaded the alternator was that I normally drive home from work at 23:30 on dark country roads and ATM all I'm using to get home is lights, not even using the heating so car is -4 degrees inside, the revs were about 2500 when I got the reading (normal driving revs heading home) the drive normally takes about 20 mins and battery was in the car when I bought it back in October

 

[Brendan W]

Motor off no load 12.6
Running no load 14.0
Running all loads on 13.1 +/- 0.1 (wipers I reckon)
Battery few months old.