Is this where the battery level should be or should it be higher?

 

Hi Watch Guy

Looks good to me and is about where I would expect to see it

 

WatchhGuy,

The only way to know if your battery is ok is to read the voltage with a meter across the battery terminals. Check it at idle and again at a fast idle (1000rpm+) With a good alternator, it'll be 14+ volts at fast idle. Check what that equals on the gauge position and yiu have your reference point.

Cheers

Paul

 

will do, thanks

 

What Paul says. This because the barrel gauges are a bit flakey.

I'll just add that pre-1988 (roughly) the alternators specified by Jaguar were just barely up to the task. Under certain conditions.......full blowers, headlights, rear defogger all in operation....it really couldn't keep up at idle speeds and the voltage would drop quite a bit. The needle might just tickle the lower red zone on the gauge. Once off idle all was well.

Circa 1988 Jaguar began installing higher output alternators.

Cheers
DD

 

That is where my 83 reads and mine is charging. I suspect I (we?) have a poor connection somewhere as voltage at my battery is higher than what my gauge reads.

 

Doug (L),

The connections on the back of the instrument cluster, particularly the earth connections are prone to deterioration, causing under-reading of some of the instruments. Adding supplementary earths can improve things.

Paul

 

they were all redone a few years ago.

 

You will never get an accurate reading from those gauges. Get a digital cigarette lighter meter and use it when you want to check.

 

On this topic, is the 115 Amp alternator from '88-'91 V12's interchangeable with the 75 Amp unit fitted to previous cars?

 

It is, but two items may need adjusting:
The long bolt the alternator pivots on might need to be thicker as the larger alternator's holes are larger diameter, which requires the fixing bracket fixed to the engine's holes to be enlarged and a long bolt of larger diameter sourced, and
The pulley on the larger alternator might be a multi-ribbed type, while you crank pulley will most likely be a V type. Just change the alt pulley to a V type.
I came across both these when I upgraded my alt, which was one of the best things I ever did on my car's electrics. The alterator drive has never slipped even though it has a V pulley.

 

great idea! I’ll give that a try, thanks

 

An even better idea is to wire a little Bluetooth battery voltage reader to the battery. An app on your phone can then read and graph voltage, do a starter voltage drop check and check alternator efficiency. Great little bits of kit, I have them on all the cars and bikes. Paul

 

that’s interesting I’ve never seen that. I’ll look into it, thanks

 

This is the type that I have. Prices vary from £15 -£50 for the same unit so shop around. The phone app is very good.

https://www.amazon.co.uk/Battery-Monitor-Campervans-Compatible-bluetooth/dp/B08VHMJYXY/ref=mp_s_a_1_1_sspa?crid=1THV1WI3797GH&keywords=bl uetooth+battery+monitor+12v&qid=1669817692&sprefix =bluetooth+batter%2Caps%2C121&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9waG9uZV9zZWFyY2hfY XRm&psc=1

​​​​​​​​​​​​​​Paul​​​​​​​