Really. These are my first days and weeks of driving this car distances after lots of work to get to this stage and things (as I expected) are popping up.

Yesterday I took a 2+ hour drive. Maybe not the best idea as I have some suspension bits that I need to get sorted, but anyway. Went see an electrician about another electrical problem with a flooded 2003 XKR. Don't even get me started, lol

They were highway miles. So, doing about 55-65 mph (88-105 kph), I would be coasting along and watching the gauges. As a person looking for signs of trouble would. I have a working volt meter (dash) and a little digital voltage display I've hooked up. For no reason, out of the blue here and there, not operating any appliances, gadgets, applying brakes - nothing - voltage would dip WAY down from 13.8 or as high as 14.2 to below 12v. Sometimes as low as 10.x and occasionally the battery warning light will begin to light dimly... It happens suddenly and disappears suddenly - returning to 'normal' 13.8 to 14.2 volts in short time... This is at a healthy and steady 2000 to 2500 RPMs at highway speed.

There is no unusual sound associated with this that I can hear.

Wondering what folks think that's all about and what I might begin to chase? I have an extra earth strap connected at the alternator harness and have spent lots of time and attention cleaning up connections... both positive and negative connections.

Bad alternator? Pully problems? Belt?
Is there a short somewhere - God forbid...?

 

Jason,

Watching the dash when driving is the problem mate.

FAITH, remember.

I suspect a loose, tired, alternator belt, simple to sort, NOT, as its the last belt off and the first belt on. 8 beers.

Alternator regulator having a female moment, NO simple cure, usually lack of use is the cause, then start using it, it has a moment. Your sparky should be able to test that in 5 minutes.

The drive pulley on the crankshaft harmonic balancer is starting to delaminate. Normal now with age. 10 beers and a few $$ for a rebuilt pulley assembly. Once all those belts are off, that pulley is a 4 minute (1 beer) task to remove. DO NOT ALLOW THAT ENGINE TO ROTATE BACKWARDS WHEN UNDOING THAT LARGE CENTRE BOLT. No amount of beer will right that wrong.

 

Thank you Grant...

I had seen this some days ago. But was getting my butt kicked by the butt end of a 1986 928... All fun and games til someone gets hurt...lol

So I looked back on the Rock Auto site just to get the specifics on the alternator I installed in the beginning of 2019. I trust Rock Auto,,, and think I can start somewhere other than the alternator, for now... At the same time is there a TEST for the regulator?

I can change the belt, no prob, and I think your right and it's due. That stupid timing cover rubber plug was leaking a little for a while,,, then a LOT for a short time. Seems a good amount of the oil ended up on the belt there and appliances...

Then last - how the HECK can I check the lamination and the condition of the pully wheel in place? Please tell me it's possible. I do have to go deeper into the belts than the alternator belt actually. I intend to run the AC compressor I don't have yet off of the crank pully directly with a very small belt. I think the V channel I'll run on it on on the the crank pully is the DEEPEST one in (of course), but still how will I know a delaminated balancer pully when I see it?

Oh and, did I say???
​​​​​​​Grant - your the Man! Word to the Mothah! Lol

 

Based on that info, and Stuttgart's involvement, I reckon the belt is your demon.

You will be lucky to "see" a delaminated pulley, until it actually seperates. A white paint mark across the outer to inner and drive for a day or 2, then inspect. If the lines still be lines, GOOD. If they be seperated, NO good.

The vulcanised section of that pulley pack is ONLY the rear "V". The rest of the "V's" are a bolt on pack to the inner section of the main pulley. I would NOT drive an A/C from that vulcanised section. Mainly *** the "V" is the narrowest of the 4. Most A/C run what is known as a "13" section belt. and the alternator is an "11" section belt. Nothing is impossible, but not for me.

 

Sounds like the crankshaft damper is shot. The test is to put a chalk or paint marker line across the centre portion, the rubber layer and then the outer ring portion that forms the alternator belt portion. Then drive the car for a while and observe the relative positions of the line; if the damper is fine then the line will be in the same place as when you marked it. If the rubber bond has deteriorated the outer pulley portion can slip and the line will no long be aligned as drawn.

However, also check the belt and it's tension with a proper belt tension gauge. Rock auto sells the Gates kricket gauge cheaply and it works well.

 

Hmm...

What is this? And importantly, what on the alternator should it be connected to? I think I had it connected to the wrong spot... This is a little black box that sits on the RH side, held down by two screws and runs to the rounding point on the RH side by the radiator. I had/have it connected to the alt,,, along with a brown wire which I think talks to the voltage gauge on the dash... Any pointers are greatly appreciated as I am under the hood now.

Thanks peeps!

 

Well! This can't be good for D voltage...
This is that YELLOW relay on the LH wall under the bonnet...
Chasing the blower relays now.

 

Is there anything that can be done to decrease the amount of current being drawn by the blower motors?

Anyone have any luck?

 

That looks like the "Load Dump Module".

I have had zero to do with them, other that what I have read over the years. Most delete them, and there are articles of how to in here I would think.

 

NOPE.

Generally an electric motor drawing excess current is a dying motor. Just like the fuel pump, usually 6amps, but I have sen sad pumps drawing 15+ before they die.

A melted re;lay is a serious short mostly.

 

Hello Grant...
Yeah, that yellow relay under the hood on the (US car) LH side. Is that the ABS relay? There is a blue and a black relay there as well. They look fine - then that big old silver one which i think is headlights - going to look "into" that one today.

When I turn my hvac blowers on they draw lots. Seems like everything does. I have to see what I can do about that...

Question - are all relays that share that 86,30, 87 & 85 (I think it is) configuration the same? I replaced the yellow with a relay (I have them all over the place) with one of those "53" relays that are used on my 86 Porsche. Seems to be working fine. I guess its the trigger or "active" side of the relay that is in question with that?

Then there's my fuel pump relay in the boot that had a mishap somewhere in this cars life time. The wire/plug/harness end (which I can splice in replacement) seems fragile. Again, wondering about relays and there inter-changablity. I cant be spending $$$$$ money like that on super specific jag relays and Im wondering what will work.

 

Where's my doggone white out pen???
I'm not out of the woods, YIT!

Although I haven't drawn the LINE across those pully-z at the front crank to check a slipping balancer and delamination, it's either that,,, or a funky battery that must be the problem...? Maybe both?

Today I drove the car over to the local big box auto supply house and the voltage on the car was acting sooo erratically, that for fear of it not cranking over due to a low battery if I shut it off, I took the door key off the ring, locked the door car running, and went inside... Them good folks are going to honor my battery warranty past the 3 yrs and allow me to UPGRADE to an AGM battery and take oft the cost of the old battery. Will have the new AGM battery tomorrow.

Anyways, went back out to the car to find it running but weirdly. The voltage at the gauge was DOWN to nothing readable and the digital gauge read 7v!!! I tried to put the car in gear and get myself home. At the moment the lights were off, no HVAC blowers, nothing - and she stalled. Wouldn't restart. No voltage, dead. I got a jump and made it home...

Earlier in the day I was working on the car trying to figure out the deal with the rear defrost (which I've needed as the back window COMPLETELY fogs in the rain) not working. Somehow or another I turned the car off for a sec with the heater blowers on for literally 10-20 seconds only, with the key at position iii lights on on the dash, blowers turning. Killed battery. It was this that made me make the trip over to the auto house FOR a replacement battery...

So, when the car is running and idling I get voltage that varies up and down, the battery isn't taking and holding a strong charge - and when I rev the car the voltage (both gauges) will go up to 13.8 up to 14.2-3 volts...

Because of the new learning (Grant) of the delaminated crank pully possibility,,, or a battery with a huge dead spot in it - or both - it must be one of them 2 things...?

Alternator is fairly new and will produce 14+volts...

Interested in what folks think. Will/can voltage be all over the place if a battery has a dead spot/cell? The battery will always start the car, holds a fair charge over time.

I have no clear answer. I got fed up today, but will go back and remove that 8mm bolt or somehow take a reading offt the alternator while it's running...?

I will paint a line over the pullies. Will use some of that good Trump money for a re-laminated pully with one of the groups mentioned here that do re-laminate-ing.

Something's gotta give!
​​​​​​

 

YES to the battery reeking havoc, followed very closely by dirty/cruddy battery cable connections, and earth point integrity.

 

No, not all the same.

Some have diodes, some have resistors, some have neither.

Some have a single "87" post, some have two "87 posts", some have an "87 post and an 87A" post.

Usually those "cube" relays have an actual circuit diagram on the case that shows what's inside.

The most common configurations are 85-86-87-30 and 85-86-87-87A-30...without diodes and/or resistors. But there are just enough exceptions to make it dangerous to assume. You gotta double check.

Cheers
DD

 

Yup.

Gotta begin with a known-good battery and good connections and grounds. Without those every test/check you perform can be (and probably will be) skewed......and down the rabbit holes you go !

Cheers
DD

 

Many many thanks!

Recently I replaced both battery cable post clamps,,, trimmed of the exposed copper,,, cut both cable covings back 1 inch back to expose new copper to clamp into the battery clamps, and removed the crud and paint down to bare metal on the ground point(s) in the boot... Thought it might but didn't solve the problem.

I'll have the battery today but don't believe it's necessarily going to be the cure to this problem.
​​​
I'm very interested in the results of the white line across the front pully (I think this is the problem) and Honestly, I'm kind of excited about doing the job of shipping it out and replacing the pully! Until Grant talked about it I had NEVER heard of delamination. My alt always "squeaked" at start up, voltage hanging reaaaly low for a good while at first (this has been getting progressively worse) and I thought it was the alt or belt (and 1000 bad connections),,, never suspecting a delaminated pully, OMG. If it wasn't for y'all,,, I would have never ever considered it.

I'll replace the pully... Unlike other machines, I LOVE working on the XJS. Solidly built and not always having to worry about bolts stripping (even though I have the issue with the 2 of 4 ball joint bolts right now), shearing and rounding... Love working on it AND it seems like a piece of art. Anywho

Understood about the relays, thank you... I didn't think ANY old relay was a plug and play necessarily, but was needing clarity on the more common 4 and 5 pronged 30, 85, 86 and 87 (a) type. I need to understand MUCH more about electrical stuff. I am lost when it comes to electrical and I get frustrated and boggled.

ps... Speaking of stripping. One of the nutts on one pin on my rear wishbones would not completely torque down, back when I dropped the cage. I'm keeping my eye on it. I have two new pins, am waiting for 1/2 20 nutts, and will be replacing those. I'm NOT looking so forward to that job! Sheeesh!

 

It's certainly possible that your front pulley is the problem, but it that were the cause I would also expect your power steering to operate intermittently and very possibly have overheating problems because the front pulley drives the water pump and power steering pump also. I am more suspicious of the alternator itself or a poor connection in the B+ wiring between the alternator and the battery. I think, but am not sure, that the alternator B+ wire goes to the starter and connects to the battery cable there. This is one likely place to have a loose or corroded connection that could cause the intermittent lack of charge.

 

Thanks D...

I will certainly check all that B+ next time I'm under the car. Soon!

And, take a reading from the alt once I learn how...
YouTube here I come.

Maybe it's different year to year? My inner most pully wheel, the one in question, has 2 belt runs. One is for the alt,,, which is ribbed and the other is the AC and blower pump (deleted). The other appliances, water pump, PS and fan are run on the outermost bolt on pullies. I just checked and DREW MY LINE... We shall see...

 

I think you answered your own question.

Its been "sqealing" and getting worse, is either of 2 things.

1) Delaminating pulley
2) Alt belt waaaaay past its use by date.

NOTHING to do with steer etc as the alternator belt on the V12 is for the alternator ONLY. OK, the went Serpentine on the later engines, but we are talking the basic engine with 4 "V" belts as factory.

 

Yup. Got ya... It's gotta be.

Good morning to ya!

Just getting ready for an overnight shift here, scraping up any hours I can get with the global pandemic fiasco! SMH. What a PITA. Looking for the Trump money...

To one other point you'd made about driving the AC (or to NOT) on the laminated pully,,, the AC and the the old (now removed) blower/air pump was driven off of the laminated pully. The second rung out from the alt belt.

I'm looking forward to the job...
I appreciate ya, Brother. Really!