Hi,

I seem to have a strange problem with my X-Type 3.0 SE Auto.

Whilst accelerating (even lightly) or climbing a hill, the voltage drops to 12v - 12.8v (lights dim down and wipers slow). As some as I stop accelerating/climbing the voltage returns to either 13.6v or 15.3v depending on how long the car has been running.

Checked the voltage drop whilst the engine is running, the negative battery cable to both the body and engine is less than 0.05v. Checked the positive which was closer 0.5v, I have now changed the positive cable which has reduced this to less than 0.05v.

Battery voltage whilst the car is off is 12.6v.

Is this normal or is there anything else I can check?

Any help would be greatly appreciated. Apologies if I've missed anything, first post.

 

I believe the X type has a 'smart' alternator, the charge output is controlled via the engines ECU which detects when a demand is being placed on the engine i.e. overtaking, and it basically turns the alternator off so it doesn't sap power from the engine, then when the load is reduced it charges again.