I always search and read before starting a thread. However, I didn't see this symptom and fix. I did break the alternator belt 3 months ago and bought a new belt which I believe to be a 5 rib prox 39" belt. I say that because when I ordered both belts I got 2 of the same with different PN's. The AC is actually 4 rib and closer to 40". Still haven't found one.

Here is the alternator behavior at present and getting worse. At start up the gauge is below 12v and stays there until I drive a minute or so AND turn at least 2000 RPM. 2 weeks ago that would kick in the charging and it would charge all during the drive. Now, same thing but any time I stop and idle, the needle drops. If I sit in neutral at 2K it stays at 14v (or more depending on how much discharge I have used starting and driving on low voltage. Now to this old hot rodder that started with regulators that had points, this smacks of a regulator problem. Seems I'm getting plenty of charge from the alt and it's not noisy.

The net tells me I can lower the alt and remove the back cover to get at the reg PCB. True? And worth the trouble? I see where buying a rebuilt unit might not be the best of all processes. I see PDB's are not very expensive. One other advantage to just R&R the PCB is to not have to move the sway bar. Unfortunately I don't have a lift, just stands.

Note: I did make a wrench to adjust the turnbuckle tensioner working from the topside. I'm 80 years old so I take what I can get.

 

I would suspect the crank damper.
They do have a history of delaminating and slipping.

 

You don't say what brand or part number the belts are.

https://www.jaguarforums.com/forum/x...ft-xjs-163573/

I found that Gates belts were longer than the OEM DAYCO I replaced. The Dayco 17380 belt is advertised as 38" for the AC belt, and 38.5 for the alternator and water pump (#5050385).

I might consider getting the Dayco branded belts and doing this again. The belts are not expensive, so I would make sure you're using what was intended.

 

Thank you, I hadn't considered belt slipping. I have had belt squeals before just like any other car and just used dressing and tightening. But they were definitely aged and cracking,. No squealing at present. I will chalk mark the alt belt and observe. Might even use an old fashioned timing light. Be back with results.

 

There is a history of both the alternator belt size ( official size dependent ) does not have enough adjustment and the other both harmonic dampener slipping driving the belt

Sqealing at any point of engine speed ?

So a easy check :

The alternator takes power to make power by a small 5 amp fuse on the right engine bay fuse box , alternator feild excitation controled by the voltage regulator inside

After the fuse the wire passes though a connector that is subject to a TSB for corrosion

From my experience the alternator comes out from the top but there is a bolt to remove from underneith

There are a few battery cable connections you can check

Beer , and will be back later with more info



Never install battery in backwards ( positive post car fwd ) and never over tighten the battery positive post bolt

Ask me how I know

 

Will check fuse and wiring connections. Still charging full 14+ V at 2K RPM and sometimes a little while below that speed. No slippage; the alt pulley is spinning at the correct speed.

 

The little 5 amp fuse should not be blown as you are getting excitation power in the alternator windings sometime ie 14 volts

The connector is one of the 2 like 13 pin square usually black or white but sometimes same color on the right chassis " rail " just behind the washer fluid fill cap

This wire goes into the alternator as the 2 small wires in the pull off round connector , clean and add some light bulb grease

Wire color X / Y

The harmonic ballancer check is to put a white paint strip across the pulleys ( no belt removal ) and after engine run with heavy electrical load the strip should line back up tegether

Could still be belt loose as hard to get difinitive proof beyond sqeel

Pics coming if they will load

 

Pics won't load , cable bill issue

If pulling alternator the long 17 mm bolt as the pivot bolt that pulls from the front and has a short shouldered bushing that stays in place

The pivot in the clevis may be pinched and the use of a long screwdriver to pry alternator out

Keep track of the 2 small wires location on the alternator other than the 2 in the round connector

The suspension cross member will be in way so alternator comes out from top

Spin up alternator at auto parts store and a preferred replacement ( for me ) is an in town alternator shop vs. purchasing a rebuild one ( they're garbage )

The VR can be changed yourself along with your diode packege if AM radio interferrence check bad , and the brushes from this brick and morter shop in Texas ( all parts in store )

Your original alternator is a Denso 120 amp

Spin up machine before installing any alternator as cheaper E - bay VRs have more faults than the broke one replaced

# IN435 Voltage Regulator for Denso Alternators, 12 Volt,On: Asuna (1993-1993) , Geo (1990-1993) , Isuzu (1990-1993) , Jaguar (1993-1997) , Jaguar - Europe (1994-1997)

 

I did read as I stated so I know rebuilt are junk. AND I have a rebuilder nearby. There used to be a couple of techs here that genuinely knew the answers beyond useable owner experiences and anecdotes. Perhaps they got tired of answering the same questions over and over. I'm sure I can pick another forum brand that uses the same alt or very close that knows what this behavior means and how to go about it. I'm leaning on replacing the regulator board but IDK where to find a good replacement. If I have to haul out the alt I might have to have a shop do this. Unfortunately I am at the point where a $500 repair is going to send this '96 XJ6 to the salvage yard. Around here in the present condition due to some rust issues around the windscreen this is a junk car. It is a great running car and has been my best car ever. Got it in 2014. Just paseed smog so I was hoping to get another year or so out of it. I'm hunting every day for my next car but after 2 Jaguars nothing is motivating me.

 

Quick wire checks


Battery cable on the top post on starter as 2 cables coming together on 1 point

You can see this through the top intack manifold between pipes 4 and 5 , A lock washer that should be sqeezed flat

Remove the battery cable on the inside of engine compartment right wheel well very near the rear firewall , wiggle with cable removed as can restrict you

These are the 2 battery cable connections aft from the alternator B + post as it goes back to battery and in parrale the rest of car fuse boxes

 

You probably need to change the ignition bulb on the dash. I bet it doesn't light up when turn the key on. The light bulb supplies field current to the alternator to start charging at low RPM.

 

That's interesting. I get a christmas array of lights when I turn the key, but which one is that exactly? I don't remember of all the icon lights which is just a "key on" indicator. If it's in one of the 2 rows, then it's good.

Well, this is weird, the new belt as of a couple months ago just snapped. I didn't hear anything but the alt wouldn't come up at all. I did smell rubber but I can't see where it slipped to where it would burn and break. I think that's end of the line for this car. Things are not going to get better.

So call this thread "SOLVED."

 

Roll the pulley and feel for ticking or roughness , this would prove the alternator insides were not running up to needed speed

Had my alternator bearing ( suddenly give up smoke ) replaced by shop real cheap for a X300 but brushes should probable need replaced also , Alternator should come out but there may be a clever way to do it on car ( ? )

At 110 K miles my brushes were as 1 / 2 wear on another X300 original Denso as a gauge

Kansasbrit , Where at in Kansas

 

I'm out by the Legends in KC.

 

What's the name of the company that buys these for parts? I got a flyer once.

 

Coparts sells them as whole cars , may not need to ship to them

Bring A Trailer , same

Trying to keep for you