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Mike, Jaguar Technician
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Hi, I. Have a 1972 V12 E type . The first sign of a problem

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Hi, I. Have a 1972 V12 E type . The first sign of a problem was that the volt gauge and the oil pressure gauge both became faulty. I have changed the dashboard voltage stabiliser as I had problems with the Fuel and Temp gauges before and thought that it may be relevant but no change. The volt gauge shows just out of the red but no charge and the oil gauge shows lower than normal pressure , do they share a common feed? I also can't get a sensible reading from the Alternator or Regulator. Does this point to the Alternator. Mitch .
Hello and Welcome..

My name is ***** ***** Im happy to help / advise you on this...

Before we progress - can I just ask exactly what is happening / what you are getting with the alternator - ?? What readings are you getting?

Plus - how old is the battery?

Rgds, MIKE.......................................

Customer: replied 3 years ago.
Hi Mike the exact problem is that up to a week ago , the volt gauge was showing the correct charge rate and the oil pressure gauge ,which is situated next to it on the dash, showed the correct pressure. Simultaneously they both stopped giving accurate readings. The volt gauge will only just creep out of the red so showing a fully charged battery, but not into the charge zone. The oil gauge will show 20/30 pounds less on start up than usual and then drop slightly as expected but never that low before. Making me think that the gauges are controlled by the voltage stabiliser unit that also control the fuel and water gauges , which I have changed.
Customer: replied 3 years ago.
Hi mike to continue, the reading from the alternator is very fluctuating not a steady rise as with engine revs . At 2000 revs it is showing about15 amps but fluctuating. The battery is about 6 years old but holds a charge fine, it shows 1340 volts not running and drops to about 1280 when started instead of rising. Hope this is of help. Thanks Mitch.
Hi there Mitch -

Thank you for your reply and further info..

Ok - we need to be looking at the battery / charge system first as anomalies there can / will cause electric gauge issues --

So- I notice you say, that engine not running , the batt voltage ( BV ) is 13.4 v ... and drops to 12.8 when started... This isn't right Mitch.

You need to have the battery checked - I hear what you say about it holding charge ok - but t could also be faulty in that its resisting charge etc,... this can mask alternator / charge issues - or complicate issues there.. In any event - have the battery tested at a garage or battery supply / car parts shop - or garage They will have a proper ( expensive !) battery test machine - or even a "drop tester" that deep cycles the battery -and that will show if you have faulty not necessarily failed battery ( cells )... and then go from there then... If the battery is identified as faulty , that then needs changing and then see how things are.

If the battery tests ok - then move on the alternator. Really this needs to be tested out of circuit - some garages have plug in equipment to do that - that is best because it tests the alternator out off circuit - so rules out any issues on car.. wiring and so on.. ( The other way is to remove it and bench test it - but its better as above obviously ..)

At this stage Mitch your problems look like battery and / or alternator . I dont know if you have checked - but if not, check the wiring for integrity -and espeically the earth connections - inc the main earths. Any earthing issues will cause these problems too... remove connections, clean and retest any iffy looking ones - and generally check even good looking ones are tight...

The BV should be circa 14.6 when running -just above idle... and about 12.8 standing... that gives you something to be aiming at / looking for.. Again, other than any wiring / earthing issues, its looking like alternator or battery we need to look carefully there -then go from there as / if needed...

Im very pleased to have helped / advised you - If you need anything else at all - by all means get back to me - Im always happy to help more if needed..

**** *** >> Meantime >>> Please do click on the "OK/ Excellent ratings" for me - Thank you in advance for that...

You can and are most welcome to get back to me anytime you might need - clicking the OK ratings does not close you out at all..

Kind Rgds, MIKE.

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