My 1997 XK8 is in the shop.
Initially it was a bad alternator/voltage regulator as it was spiking voltage when above idle.
Now that has been replaced and it's only delivering 4.5 volts to all of the fuse boxes.

The repair shop is scratching their heads as where to look for a possible issue and each time they scratch it's costing me $100.

Any insight as to where to look for potential issues would be helpful.

Thank you all in advance.

Mark

 

Stupid question, but always worth asking: they checked the battery (and connections), right?

 

That was my first question so not stupid.
New battery and connections are tight.

 

What is the voltage across the battery terminals?

 

Thank you for responding.
Unfortunately I will have to wait till Tuesday to get that answer.

 

Check the voltage directly off of the alternator terminal. If it reads really high (+40v) it indicates you have an open in the cable between the alternator cable and wherever it terminates on our cars.

If it reads low (-14v), I'd call it a defective alternator.

Think this through. Assuming you started the car off of the battery, it had to be in a good state of charge to supply all the needed systems. So it was definately more than 4.5 volts which you say you are reading at the fuse boxes. Or did you jump start the car?

Something doesn't add up.

 

Well,

first question is is whether the new alternator is brand new or a rebuilt unit. Rebuilt units are a bit of a lottery.