Howdy everyone!

I知 the proud owner of a 1995 Jaguar XJ6 (X300) with a 4 L 6 cylinder and have a problem. It basically consists of two symptoms:

1. The battery does not charge properly: After starting the car, the voltage on the little front display shows something around 10 V. It then rises a little to about 11 V when driving, and on the highway/freeway - so at constant, higher engine speed - climbs up to right below 13 V. I think fully charged, the battery used to have around 14 V on the display, so for some reason the battery does not charge more that that. NOW: Whenever I come to a stop (eg: get of the freeway to a light) the voltage suddenly drops significantly - sometimes to 11 volts, sometimes further or less. This also happens when turning on the lights (I know a little dip is normal - but it dips a lot) and once again only recovers when driving at higher engine speeds for a while. I noticed that the drops seem to correlate with engine speed.
2. The battery slowly but surly drains when the car is turned off and standing for a while and is completely empty if I do not turn it on for 3-4 days depending on how the charge was before.

-> After testing it multiple times, I知 positive the battery is fine. Of course, I figured there was something wrong with the alternator, and so did the test at Autozone. But changing the Alternator did not help or change anything.

When having the alternator tested at Autozone, I was also told, that the starter is faulty and that a faulty starter could affect the alternator. But the car starts up perfectly fine, even with low battery charge. Does anybody know if it might actually be the starter?

One of my thoughts was, that maybe the connection from the alternator to the battery is bad, causing the alternator to struggle charging the battery. Any thoughts?

I look forward to your input and ideas! And if you have/had a similar problem - please share! I can use all the help I can get.

Thank you!

Felix

 

You may have a slipping harmonic balancer pulleys slipping from each other driving the alternator belt

Do not remove the belt for test and the marks should line back up after engine shut down , common issue with X300 from reading

The alternator belt lenght is critical and some new have been too large

there are 4 terminal post between the battery and the alternator

exactly where the instrument gauge is sensing the voltage is not clear to me

the problem with the auto parts store spin up machine is very little electrical load demand and not a warmed-up alternator like in real world.

 

Thank you Parker 7! I will definitely check that out! Do you know if there is an explanation for the battery drain, connected to that issue?

 

If as soon as the engine is rotating the voltage gauge should be above a fully charged battery of 12.75 to around 13.5 to 14.5

if the gauge is reading 10 then you have insufficient voltage to charge the battery

A still car battery drain ( parisitic drain ) can come from the security lock control module not going to sleep

a quick thing you can do is turn the rotary switch on the steering coluum to off

Do you have a stuck steering coluum movement ?

 

You have an alternator problem. As Parker says you should be seeing around 14 volts.
Testing an alternator without a suitable "dummy load" will not give you a proper indication of the alternator's serviceability.
Alternators will give full voltage right from idle to full RPM. Your alternator voltage variation with different speeds is not normal.
Because it is partially working, I suspect your alternator has failure in the diode plate.
Otherwise, a loose drive belt could be the problem.

 

As Parker 7 said there are 4 terminal post between the battery and the alternator" my problem was a short at the right front firewall post (LHD car) where the rubber insulator have deteriorated and and the posst was shorting out to the firewall.

 

Yes, the steering wheel is locked when the car is off.

Are you referring to the rotary switch on the right side of the steering column - right below the blinker?

 

Okay, that's good to know. I already changed the alternator. So the problem has to lay somewhere else. The drive belt is just a couple months old and hasn't been slipping.

 

Yeah, I will definitely check those.Thanks

 

To check the terminal post you would have the remove the heavy cable and then wiggle.

on the other side of the sheet metal is the other cable which the other has been found to be loose by wiggling the terminal post end exposed to you pointing toward the engine bay

This will be on the right front wheel well and bot the rear firewall.

The first terminal post aft of the alternator is the starter solenoid. which is 13 mm on a 3 inch ratchet extension

Someone got a really good pic of his as his was loose causing charging issues.

On the steering column it is the up and down / fore and aft extension

The column switch is the large one with the auto / off positions.

Never assume the parts you get are good out of the box