s-type 4.0 v8 problem with bat/Alt?

[andysv8]

I bought the car not long ago and the battery light was on, when I bought the car the bloke said that he has put a new 110 battery on rather than the 100, when driving the car few days later all electrics cut off e.g windows radio, all dash, window wipers and sat nav. I found out that the alt was overcharging the bat so electrics cut off for safety, I changed the alt and still have the same problem, had battery checked and its only holding 47% but completely died today, could this possibly be the battery causing all this chew and why is the alt still reading that its overcharging? any help id be very grateful!

 

 

 

 

[Old Peter]

Hi Andy, and Welcome to the club.

 

Apparently batteries nowadays don't just gently die, but just go quickly.

 

I would guess that it is the battery.

 

Regards,

 

Peter.

[andysv8]

Thanks peter, and cheers for the welcome! :) ill change the battery and go from there, hopefully it solves the problem.

[Jaguar Owners Club]

Hi Andy...and welcome to the club!

 

Peter may be correct with his diagnosis of the battery.

If the battery is not suitable for the car then it could cause an overcharge situation but there are other variables as well.

Generally, a battery does just one job...hold a charge whilst the alternator is not recharging it (e.g. engine off).

I would look at what is coming out of the alternator (amps, volts) they should be within 12.8 and 14.4 volts ideally and the current will alter depending on the load applied to the electrical system (e.g. headlamps, heater all on) and should not be outside of the specified range.

 

Regards    Trevor

[andysv8]

Hi Trevor, thanks for the info, the alternator is reading at 15 and goes up to 17 when I give it a rev but so did the old one and the same thing happened that all the electrics are on when I start the car and as soon as I start to drive or put my foot down they cut off and the lights go really bright, with the first alt overcharging I thought that it was that causing the problem but now Iv changed it its doing the same thing, it has me baffled to be honest.

 

thanks for your help and time, Andy.

[Jaguar Owners Club]

If the alternator is reading 15 to 17 volts then I would be very concerned...that would indicate an overcharging situation.

[andysv8]

That's what I cant get my head round, with me changing the alternator it should be ok but its still overcharging

[Jaguar Owners Club]

I would probably advise you to get it check by an auto electrician before any real damage occurs to the electronics.