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JagDoc, European Shop Owner
Category: Jaguar
Satisfied Customers: 6457
Experience:  20 years of experience working with Jaguars. Independent European shop owner and technician.
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new battery new alternator still not charging where do i look

Customer Question

new battery new alternator still not charging where do i look next
Submitted: 8 years ago.
Category: Jaguar
Expert:  JagDoc replied 8 years ago.
Please connect a jumper cable ground between a good engine ground a good chassis ground and tell me if that helps the problem.
Customer: replied 8 years ago.
Made sure i had a good ground no difference
Expert:  JagDoc replied 8 years ago.

Have you tested directly between the alternator positive post and engine ground? We're trying to determine if

1) the alternator is functioning


2) if we have a ground or wiring problem somewhere along the way.


What are you using to test for voltage?

Customer: replied 8 years ago.
here is what i know: i traded a car i had for the jag it drove fine when we took it for a test drive. On the way home the guage on the dash of the car indicated that the battery was no longer charging. by the time we got home(about 15 miles)the battery symbol on the dash was incircled with a red box. The owners manual told me this ment a charging problem or a bad battery. I have since replaced both(battery & alternator) with no improvement. I don't know what to check for next. As it was working when we got the car i was guessing it was a component failure, so i've replaced what i know to replace. I talked to a jag guy here he told me to check the "dump valve" i don't know what that is or where to find it on the car. that is the full extent of my knowledge of this car.
Expert:  JagDoc replied 8 years ago.

I'm not quite sure what the dump valve is that he's referring to either, but vehicle electrical systems all have certain commonalities.


First point of order:

Get a multimeter, and hook one lead to the large terminal on the alternator, and one to a good engine ground. If you have a good 14.5v or so while running, then you've got yourself a ground problem between engine and chassis. If you don't, then it's possible that you have an engine wiring issue, but more likely that you have a faulty alternator.


Please check this, and let me know what you find.

Customer: replied 8 years ago.
Checked voltage its fine i also added a ground strap between engine and chasis to rule that out as a possibility. as the car was running fine when i got it i don't seee how it could be a engine wiring issue. what wiring could it be
Expert:  JagDoc replied 8 years ago.
So what you're saying is that the alternator is functioning, but you're not seeing that same voltage at the battery?
Customer: replied 8 years ago.
What i'm saying is that the gauge on the dashboard shows a red box surrounding the battey icon and the voltage indicator shows a "9" volt output. Giving the car more gas to speed up the engine dose not affect the "9" and if i drive the car the battery drains . I can charge the battery with a charger but the car repeats the above sequence. That is why i thought it was the alternator, but to be sure it wasn't the battery i replaced it first then the alternator. Still no change. I was wondering if there is a fuseable link or perhaps a relay that I'm overlooking