Amp Meter

PAUL MORRIS · Post by **PAUL MORRIS** » Thu May 20, 2010 8:31 am

Dear All,
I have just a small question on the Amp meter of a 4.2 of 64.
While driving without the lights on its in middle position after some time
but if headlamps are on its about 3/4 to the Decharged level.
Is this normal or should I change the battery or something.
Thks

Post by **Heuer** » Thu May 20, 2010 9:35 am

Yes that is normal. To be honest the Ammeter is no great help with an alternator equipped car - it is a hangover from the dynamo on the 3.8 and Jaguar did not bother to fit the more appropriate Voltmeter until the S2. You can fit a Voltmeter if you want: http://etypeuk.com/forum/viewtopic.php?t=166

PAUL MORRIS · Post by **PAUL MORRIS** » Thu May 20, 2010 12:12 pm

Dear David,
Thks for the detailed Reply & Excellent Link, your Forum is just excellent.
Paul

S12+2 · Post by **S12+2** » Wed May 26, 2010 3:14 pm

Many thanks for posting this information. I have purchased a Voltmeter and will be carrying out the change shortly. Before I do, I have one query about my standard Ammeter setup.

I've just returned from a trip to France and the Ammeter reading has been odder than normal. Usually on a journey it flicks over to 75% charge and then after a while returns to near the centre and so on throughout the journey.

On this trip it flicked over to 75% charge after about 10 minutes running and then stayed there until the engine returned to idle. The battery is on an Accumate in the garage so was fully charged.

Has something in the voltage regulator/alternator failed and should I worry about it? Is the battery being overcharged? I can't see any problem with it and it doesn't seem to get hot. Any tips would be greatly appreciated.

Many thanks

Nick Morgan

Post by **Heuer** » Wed May 26, 2010 3:52 pm

Nick

Did you have any lights or heater fan working because anything switched on will draw power and the voltage regulator will ask for charge to compensate. On an alternator equipped car the ammeter will just show 'charging' and will not tell you if there is another problem. An overcharged battery will get very warm and the acid level will quickly drop through evaporation of the distilled water. In extreme cases acid will bubble through the vent holes. Easiest test is to put a voltmeter across the battery terminals with the engine running - it should read about 14 volts.

I always carry one of these in the car toolkit as it can quickly tell you if and where you have a problem: http://tinyurl.com/2vwj2g2

S12+2 · Post by **S12+2** » Wed May 26, 2010 7:00 pm

Thanks for the reply David. The only thing using current was the satnav but I guess that wouldn't use much. I'll borrow a voltmeter from my neighbour and report back.

S12+2 · Post by **S12+2** » Thu May 27, 2010 4:36 pm

Hi David

I tested the charging circuit as you suggested and obtained the following:

Engine off - battery reading 13.7V and normal water level.

Engine running - reading 14.2V at 2000 rpm.

The ammeter was showing it's normal one quarter on the charging side.

Nick

Post by **Heuer** » Thu May 27, 2010 4:56 pm

Nick

Your charging system seems spot on at 14.2v so it does not seem you have a problem.

Nick · Post by **Nick** » Thu May 27, 2010 8:05 pm

Another Nick experiencing a similar problem !

My ammeter (s1 4.2) has been showing half full charge whilst driving with no load from lights etc. The battery electrolyte level was mostly at 'good' (1.275) with 2 cells at 'fair' (1.25) but the no-load battery voltage is only 12.6volts. The voltage with engine running at idle is 16.3V. Electrolyte has been coming out through the overflow pipe.

Presumably if the battery voltage doesn't rise towards 14V, the 4TR regulator continues to charge the battery. I might try another battery to see what happens. The 4TR looks like it is original. I read that the 4TR voltage can be adjusted - worth trying ?

Sorry to hijack your thread Nick !

Nick L.

Post by **Heuer** » Thu May 27, 2010 8:22 pm

Nick L

Sounds like your 4TR is knackered and overcharging the battery which is not good. Overspilled acid will destroy your paintwork and the fumes produced are explosive and highly corrosive. You should replace both the regulator and the battery, the latter will have been permanently damaged.

I would not bother trying to adjust the regulator as it is sealed and requires specialist equipment to set it correctly.

S12+2 · Post by **S12+2** » Fri May 28, 2010 8:02 am

Thanks David, I'll do the Voltmeter conversion and keep an eye on it

Nick No.1

Nick · Post by **Nick** » Thu Jun 03, 2010 8:30 pm

David - sensible advice as usual. A new 4TR seems to have cured the overcharging:down to 14V now and ammeter on centre. I'll see how the old battery responds to some TLC.

Nick L.

christopher storey · Post by **christopher storey** » Thu Jun 03, 2010 9:15 pm

The definitive answers to these problems are given on this site :

http://www.mez.co.uk/lucas.html

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