Grrrrrr

Technician, Bodgit & Scarper Ltd

Full Member

• Oct 18, 2024

• #1

Not the Rangie but the Jag, more specifically, its alternator.

The battery is only a year old but a few times recently it felt a bit sluggish on turnover. Charged the battery and then started it and tested voltage across the battery - 13.7V. switched on every electric thing I could find and still 13.7V. Now that's a bit low but I think it might have one of those smart alternators that adjusts the voltage depending on the state of the battery which then leads to the question: how do I know if the alternator is acting up?

 

Grrrrrr

Technician, Bodgit & Scarper Ltd

Full Member

• Oct 18, 2024

• #2

Even more worrying, it is a 2001 S-type and there appears to be an early and a late alternator. The early one doesn't seem to have an aftermarket alternative! The genuine one is eye-wateringly expensive.

 

R

roythebus

Active Member

• Oct 18, 2024

• #3

Try the old-fashioned drop test across the battery.

 

Grrrrrr

Technician, Bodgit & Scarper Ltd

Full Member

• Oct 18, 2024

• #4

Oh, bugger. You need an oscilliscope.

"The signal from the ECU to the alternator should be a square wave pattern that will change with load request.

“If there is no change in the pattern this signifies no request from the ECU, and further investigation is now required on the vehicle.”

 

Datatek

Well-Known Member

• Oct 18, 2024

• #5

Grrrrrr said:

Oh, bugger. You need an oscilliscope.

"The signal from the ECU to the alternator should be a square wave pattern that will change with load request.

“If there is no change in the pattern this signifies no request from the ECU, and further investigation is now required on the vehicle.”

Click to expand...

As you have discovered, it's not the alternator that is smart but the regulator and the way that the regulator is controlled. It may be possible to fit a standard alternator?

 

Grrrrrr

Technician, Bodgit & Scarper Ltd

Full Member

• Oct 19, 2024

• #6

Datatek said:

As you have discovered, it's not the alternator that is smart but the regulator and the way that the regulator is controlled. It may be possible to fit a standard alternator?

Click to expand...

Maybe!

I rang Jaguar but the guy just said my alternator was obselete so no joy there. I suspect with mine being a 2001 it may not even be a smart regulator. Again, I asked Jag but he didn't know as he mainly worked on Land Rovers. He gave me some part numbers but I haven't had much luck with finding a decent part at a decent price.

Easiest thing might be to get it refurbished. It can only be the brushes or the regulator, or possibly the controller if it is a smart one.