Can anyone advise me please just bought x type 2.5 2002 and have been told by my mechanic friend that the output voltage from alternator is reading 15.5 when most of cars he has worked on are 14.6 .is this 15.5 ok and also what is the best site for parts cheers Bill.

 

Elvo, 15.5V is a bit high. Granted, if this is being measure right after the car is started, it may be not too far off. But then, I would be looking at the battery cables first before you get too far. Based off of that voltage, the ECU is not seeing a proper voltage inside the cabin of the car. So, you are getting a voltage drop somewhere. You can put your hand on the battery cables and see if one of them is warm/hot to the touch. If so, that cable is bad. I would also measure the voltage across the battery. If the alternator is up at 15.5V but the battery (when measured with the leads only touch the lead post o the battery, not the clamp) is down around 13.7V or so, then that would point back to the cables. If the battery is up high too, then I would do a voltage measurement inside the cabin of the car and see if that is reading the same. If it is, then that points back to the alternator. If no, then the power wire between the battery and the passenger fuse box has an issue.

On a side note. The car is programmed to artificially raise the voltage right after starting the car to top off the battery, replacing the energy pulled out of it to start the motor. It does this by raising the voltage above normal to force the battery to take a charge. Normally it will only get up to 14.6 VDC. So, even the 15.5V is still a bit high. Hence why I am pointing out the battery cable issues. The only other thing could be the field wire to the alternator is shorted to a power wire. So, that is forcing the alternator to output a maximum voltage and override the ECU signal.

 

Saw these

Alternator over charging RAC man reckons ?

With the next one it wasn't the alternator, so as Thermo says, check other things too

Charging voltage is 15.56v - Page 3

No best site really as they all run various offers at different frequencies, but a few are

Alternator | High Quality Alternators For All Cars | Cheap Alternator

Alternator | All types of Alternators for every make and model

Jaguar X Type | Jaguar | British Parts UK

 

Thanks for reply ...are you saying that normal voltage output is 15.5.

 

15.5V is too high, when that happened to me the battery had a bad cell & needed replacing. 14.4V should be the most you normally see.

 

Cheers Cambo. Will investigate.

 

It all depends on when and why. A constant 15.5vdc is too high but it may not be the alternator at fault.

 

Thanks mikey