Hello all,
My alternator light stays on while the engine is running. Voltage gauge reads 13 volts.
Using my DVOM I have a reading of 17-18 volts at the double brown wires coming off the alternator to the firewall on the drivers side.
At the battery I also have 17-18 volts between the terminals.
As everyone knows, alternator removal is a PITA. I read a post from someone who stated that this could be the voltage regulator and I concur. However, are there any other checks I should do before replacing the alternator or is there the possibility of obtaining the voltage regulator and replacing it myself. I believe it is held by screws behind the black cover on the alternator. If so, where can I purchase the regulator rather than purchasing the complete alternator.
frank

 

On the how:
Jaguar voltage regulator XJ6

Not sure about where to get the part though.

 

Have a look at this link... For my XJ type III it contains a diagram and guide how to disassemble the alternator: https://www.jaguarforums.com/forum/x...ams-faq-34885/

 

Clever about replacing the regulator without removing the alternator.

However, also very misleading. The a/c compressor and air injection pump absolutely do not need to be removed to get the alternator out of the car!

Cheers
DD

 

Good corrective note; I have yet to attempt such a procedure but remember coming across it in my reading.

Frank, you may try everydayxj or Welsch Enterprises online to see if they have any.

 

Doug, you are quite correct.
I am just going to do it the way I did before, by disconnecting the drivers' side sway bar link and just loosening the passenger side. if the regulator is available, I will remove the alternator from the car and do a complete service. Just checked and the asking price for a re-manufactured bosch alternator with no pulley is about $240.00. Made a contact with a guy who has a couple of used alternators for $75.00 each. I had taken out this alternator before because the brown wires shorted out and burnt up (melted)the auxiliary fan relay connector. It was oil soaked and I took it apart cleaned it up and it worked properly for about six months until this problem started. I will call Welsh and see what they have then make a decision as to what to do.
Thank you guys
Frank

 

Im tracking a rebuilt alternator for a Series III for 125.00 on E-Bay.

 

I installed two alternators today with the same result;
Original Lucas: Battery light ON voltage at firewall and battery 17.5 volts
Motorola NEW: Installed on car: Result 17.5 volts at firewall and battery. Battery light on dash OFF
Lucas USED: Tested good.Installed on car: Result 17.5 volts at firewall and battery. Battery light on dash OFF
Am I nuts or do I have three bad alternators.
I am taking all three to an Alternator shop to have them tested.

 

Hmmmm.

I can't think of anything the *car* can do to drive voltage that high. But having three units with the exact same 17.5 voltage is surely weird.

Have to do some mulling.....


Cheers
DD

 

Depending on what the regulator circuit is like for this model, the problem is likely external to the alternator/regulator assembly. The regulator may not be getting all the signals it needs to regulate the voltage, so you need to check all the wires aside from the B+.

 

I am returning the Motorola Alternator to the parts store for a refund. The output on both Lucas Alternators when tested at the rebuilder shop is averaging 14.7 volts. so, both my alternators are good. On the car the output is 17.5 volts. I am in the process of looking at the wiring from the switch, battery light and the 10 gauge wires to the firewall. Could a faulty ground cause this? I am also going to rebuild the original Lucas alternator. I found a place in Brewster New York that sells the parts for the Lucas Alternator. For those interested in the regulator and brushes, Go to classicgarage.com. The phone number is 845-940-1900. The physical address is 945 Route 22, Brewster, New York 10509.
Regulator $30.00 Brushes $22.00.
Will keep you all informed of my progress.

 

Yes a faulty ground could be a problem because the internal regulator wants to regulate to 14.x volts above ground. If the ground floats, then the ground reference is not accurate.

 

Which on these cars is easy, as only two wires are involved, the brown excitor wire and the large B+ wire.

There have been a few cases where the B+ wire has developed excessive resistance....although this typically results in a low voltage reading at the battery.

There have been many cases of loose/broken/otherwise faulty excitor wires. Not sure if that would cause very high output, though.

Cheers
DD

 

hedging here due to unfamiliarity with the particular system ... but some regulator designs default to 16V if they lose the signal from what is apparently the "L" lead on this alternator. Others default to 13.5V.

Is the alternator lamp the correct size bulb? Some regulators are dependent on the bulb being in spec.

 

A possibly stupid question as well, if using a multimeter are you sure you have the dial on the right setting? Can't be you have 3 bad alternators.

 

RESOLVED: <I am so pleased right now>
So plums was right. Having exhausted all options, I decided to look at every single ground point on the car. I cleaned and replaced any cable/wire that did not look shiny copper. Some were green and some were black. I also found a braided wire hanging below the intake, which should have been connected with the multiple grounds at the rear of the intake manifold. I added an extra ground from the battery to the engine block. When done, I started the car and magically my alternator output is now 14.5-14.7 volts. I had a slight engine misfire which has also disappeared. I have never had this engine working this smooth. Lights that I was going to work on suddenly lit up. Car now starts within a second or two of cranking. MEMO TO ALL: Check and replace/service all grounds on your car. I am going to continue to look at all the ground points inside the car. I have been working on cars for the last fifty years and never saw anything like this.I am totally in awe at the results. THANK YOU ALL FOR YOUR INPUT ESPECIALLY 'PLUMS' who hit the nail on the head. Hooray to all at the JAGUAR FORUM. You guys are great. Who would have thought that the grounding system, even though it was "FUNCTIONAL" would be the cause of so many problems.
PS: I am even hoping that by tomorrow it will fix the slow leak I have on my right rear tire. LOL> Kudos to all

 

Great work !

Good suggestion, Plums!

Cheers
DD

 

There is one more ground you're going to love getting at again ...

... the alternator mountings are effectively the companion side to your B+ cable.

Ideally you need the faces of the mounting ears and the mating surfaces on the mounting points to be bright and shiny before you bolt them up. On some cars, this joint has never seen the light of day since it left the factory and no one thinks of cleaning it because it does not dawn on them that it anything other than a mechanical connection. The electrical function just does not come to mind.

 

Plums, dedraden, Doug, and any others who could possibly help:

This exact problem has crept up on me now in my XJ6. Alternator light comes on full strength then goes off then returns dimly almost immediately and then waivers in brightness according to my use of electrical devices. These symptoms are occurring in addition to the ones you outline and unless I'm mistaken they all point me directly in the same direction of cleaning the ground points. However, I'm not familiar with the process of cleaning these ground points and I'm not sure what you all are referencing as the B+ and brown exciter wires. Any pictures or descriptions of exactly where the wires should be grounded would be incredibly helpful as I mentioned I have not done this before and it appears my car could benefit greatly from this simple procedure.

Edit:
I should've noted - the alternator is successfully charging the battery after both short and long drives and the belt is not broken.