• Advertisement
Xclusively Jaguar
SNG Barratt
David Marks Garages
Make a donation to XJ40.com

Faulty Alternator??

Meeting room
Chris Barney
Snr Member
Posts: 357
Joined: Mon Jun 30, 2014 8:15 pm
Location: Leicestershire

Faulty Alternator??

Postby Chris Barney » Mon Dec 23, 2019 1:29 pm

Nice sunny day so took the old girl out for a good run. About 19 miles in, noticed charge had dropped from 13v down to around 10v. Got her home multi meter on with engine running on 11.40. I assume my first point of call is replacement Alternator??
Changed both auxiliary belts 3 weeks ago and things been ok up to now. In the past the gauge has dropped before, but gone back to normal 13v charge on restarting.
Advice please. Naki have you got one for a 3.6??
88 Sovereign 3.6 Auto vin 556271
2010 Q5 2.0 TDI SE
2008 A4 1.8T S Line (DSG)

naki_k
Super Moderator
Posts: 28912
Joined: Sun Feb 21, 2010 9:25 pm
Location: Kirton, nr Boston, Lincolnshire

Re: Faulty Alternator??

Postby naki_k » Mon Dec 23, 2019 5:44 pm

Check the belt tension is still ok. Especially since the belts have just been changed.
Then can slacken off/ stretch a little as they settle in.
88 3.6 XJ6 PDH/CEM
90 Range Rover Vogue SE 3.9 V8 LPG
91 4.0 XJ6 Manual
92 4.0 XJR Manual
92 4.0 XJR
93 3.2s - 4.0 Manual conv
93 4.0 Sovereign
93 6.0 XJ81 DD6 x2
93 6.0 XJ81 XJ12
94 4.0 XJR
94 4.0 Daimler
96 4.0 X306 XJR
96 4.0 X300 D6
97 4.0 X300 Sport Manual
2000 LR Discovery ES TD5 A
Breaking 40/ 300

Brake buster
Snr Member
Posts: 724
Joined: Sun Jul 03, 2016 8:18 pm
Location: Gloucester UK

Re: Faulty Alternator??

Postby Brake buster » Mon Dec 23, 2019 6:03 pm

also the grounding strap etc , and the battery terminals are not corroded

they you can confirm the alternator is at fault

BB
1994 3.2S in Morocco red and Doeskin/Ruby red interior
1989 V12 XJS White with Mulberry interior
2015 XF Sportbrake Luxury 2.2D Turbo in British Racing Green Metallic

Chris Barney
Snr Member
Posts: 357
Joined: Mon Jun 30, 2014 8:15 pm
Location: Leicestershire

Re: Faulty Alternator??

Postby Chris Barney » Mon Dec 23, 2019 6:43 pm

The belt seems tight, if anything too tight. Battery terminals clean, will check grounding strap. My instinct is alternator, possibly voltage regulator. Has it has done this before but normally on start up then increases to 13v
88 Sovereign 3.6 Auto vin 556271
2010 Q5 2.0 TDI SE
2008 A4 1.8T S Line (DSG)

naki_k
Super Moderator
Posts: 28912
Joined: Sun Feb 21, 2010 9:25 pm
Location: Kirton, nr Boston, Lincolnshire

Re: Faulty Alternator??

Postby naki_k » Mon Dec 23, 2019 6:44 pm

You could try the voltage Reg first, as it’s easier to access.
You can also put a multimeter off the back of the Alt, to see what’s coming directly out of the terminals
88 3.6 XJ6 PDH/CEM
90 Range Rover Vogue SE 3.9 V8 LPG
91 4.0 XJ6 Manual
92 4.0 XJR Manual
92 4.0 XJR
93 3.2s - 4.0 Manual conv
93 4.0 Sovereign
93 6.0 XJ81 DD6 x2
93 6.0 XJ81 XJ12
94 4.0 XJR
94 4.0 Daimler
96 4.0 X306 XJR
96 4.0 X300 D6
97 4.0 X300 Sport Manual
2000 LR Discovery ES TD5 A
Breaking 40/ 300

Chris Barney
Snr Member
Posts: 357
Joined: Mon Jun 30, 2014 8:15 pm
Location: Leicestershire

Re: Faulty Alternator??

Postby Chris Barney » Mon Dec 23, 2019 6:54 pm

Will our meter on alternator as suggested. Not sure how to access regulator or test it. Will drop it down to local garage when I’m back and get them to check it. Then if it’s the alternator can get you to courier one and they can fit it. Is the courier 48hr
88 Sovereign 3.6 Auto vin 556271
2010 Q5 2.0 TDI SE
2008 A4 1.8T S Line (DSG)

Chris Barney
Snr Member
Posts: 357
Joined: Mon Jun 30, 2014 8:15 pm
Location: Leicestershire

Re: Faulty Alternator??

Postby Chris Barney » Tue Dec 24, 2019 4:31 pm

Naki, BB, ‘law of sod’ disconnected battery, reconnected, fired her up. Guess what 14.4v. Left her running 15mins, no change.
I really should have faith in the old girl.
Naki be in touch new year for a later version CPS to bastardise with my original multi plug.
Thanks again for advice
88 Sovereign 3.6 Auto vin 556271
2010 Q5 2.0 TDI SE
2008 A4 1.8T S Line (DSG)

naki_k
Super Moderator
Posts: 28912
Joined: Sun Feb 21, 2010 9:25 pm
Location: Kirton, nr Boston, Lincolnshire

Re: Faulty Alternator??

Postby naki_k » Tue Dec 24, 2019 11:21 pm

Chris Barney wrote:Naki, BB, ‘law of sod’ disconnected battery, reconnected, fired her up. Guess what 14.4v. Left her running 15mins, no change.
I really should have faith in the old girl.
Naki be in touch new year for a later version CPS to bastardise with my original multi plug.
Thanks again for advice


Ok good news.
The early model Bosch alternators are usually pretty reliable really. Unlike the post 92 Denso units.
CPS- best to buy a new one. Rather than another used part.
88 3.6 XJ6 PDH/CEM
90 Range Rover Vogue SE 3.9 V8 LPG
91 4.0 XJ6 Manual
92 4.0 XJR Manual
92 4.0 XJR
93 3.2s - 4.0 Manual conv
93 4.0 Sovereign
93 6.0 XJ81 DD6 x2
93 6.0 XJ81 XJ12
94 4.0 XJR
94 4.0 Daimler
96 4.0 X306 XJR
96 4.0 X300 D6
97 4.0 X300 Sport Manual
2000 LR Discovery ES TD5 A
Breaking 40/ 300

Chris Barney
Snr Member
Posts: 357
Joined: Mon Jun 30, 2014 8:15 pm
Location: Leicestershire

Re: Faulty Alternator??

Postby Chris Barney » Tue Dec 24, 2019 11:29 pm

Ok I’ll buy a new CPS. But still need to replace front headlights modules, so will be in touch
88 Sovereign 3.6 Auto vin 556271
2010 Q5 2.0 TDI SE
2008 A4 1.8T S Line (DSG)

naki_k
Super Moderator
Posts: 28912
Joined: Sun Feb 21, 2010 9:25 pm
Location: Kirton, nr Boston, Lincolnshire

Re: Faulty Alternator??

Postby naki_k » Wed Dec 25, 2019 12:14 am

Chris Barney wrote:Ok I’ll buy a new CPS. But still need to replace front headlights modules, so will be in touch


Ok. There’s always the next thing.
I have front modules no problem.
88 3.6 XJ6 PDH/CEM
90 Range Rover Vogue SE 3.9 V8 LPG
91 4.0 XJ6 Manual
92 4.0 XJR Manual
92 4.0 XJR
93 3.2s - 4.0 Manual conv
93 4.0 Sovereign
93 6.0 XJ81 DD6 x2
93 6.0 XJ81 XJ12
94 4.0 XJR
94 4.0 Daimler
96 4.0 X306 XJR
96 4.0 X300 D6
97 4.0 X300 Sport Manual
2000 LR Discovery ES TD5 A
Breaking 40/ 300


Return to “General Chat”

Who is online

Users browsing this forum: No registered users and 1 guest