Haven't driven the car for a while, drove it for a day went to park put it in reverse All of a sudden dashboards flickering Car is running, set in reverse but cant change gears. Shut down the car restart, everything's fine. Next day go for a long trip 3 hours away on the way back home about an hour and a half left I get a charging system warning light. Plug in an OBD2 monitor voltage they are a 12.7 And keep going down, at some points voltages started going up to 14 and back down. long story short was a nerve-wracking experience, made it home at 11.4 volts and driving without headlights for the last 30 minutes 😆. Let the car rest overnight started up alternator seems to be working fine again.
You guys think the alternators failing or can it be anything else such as battery issue! Replaced the battery couple months back, now thinking maybe the alternator was failing slowly.

 

Check the battery terminal for lose connection, but this is a long shot. Either your alternator are going or your serpentine belt is slipping.

 

Something strange is going on for sure

 

Check for oil leaks damaging the alternator.

 

Update:
I replaced the voltage regulator that sits in the trunk quarter panel, since it was cheap on eBay for around 20 bucks.
This did not help at all.
The car seems to be at minimum of 14 volts coming from the alternator when car is running.and then it goes up to 16 then 0, lights on dash and temporarily flicker and engine speed slightly changes, goes back to 14 and then keeps on going back to 16 and repeating the cycle. Noticed some oil leaking on right side of the engine around the alternator area and I think it might have oil on it and maybe that's part of the culprit probably damage the alternator.

 

Do you have anything plugged into the OBDII port? If so, unplug it after you shut off the engine. Leave it unplugged until you need to use that device again. My dashboard went bonkers because I left my ELM327 dongle plugged in to run the Torque app to display oil pressure and water temperature gauges. My dealer's Service Advisor told me to unplug it when I shut off the engine.

If that's not the cause, my bet is that your battery is low.

 

Alex, my tech confirmed leaking valve cover gaskets killed my alternator. I got a new one relatively inexpensively from FCP Euro for under 260 - OE Denso, with lifetime warranty.
https://www.fcpeuro.com/products/lan...1g#description

Still, I've kept the old alternator to see if it can repaired...

 

Thanks yeah I'm suspecting this is the case here as well.
Did you get your oil leak fixed and what did that run you?

 

Yep I'm aware sometimes this can be the case, unfortunately not in mine

 

If you have a working SDD I would suspect problems with the BMS. Hard to say as this is just a guess without any codes to guide us?
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Good question, Alex. Getting to the valve cover gaskets is not cheap as the supercharger and so much else is in the way. One tech quoted me 3,000; another said he would have to think about it and never got back to me but said "that's a big job", and my tech quoted me 500, but when he saw it was supercharged he called and said that should be 1500 but as I said 500, I'll do it for 800 and threw in an oil change. Great guy. So it was 800 + price of gaskets. I would strongly recommend you consider replacing the plastic coolant pipes and water pump with A) metal and B) 7th edition water pump, while you are in there. One way you can find out if your tech is any good is to see if he has the right tool to remove the injectors.... (not everyone does) Also, some alternators can be cleaned up and repaired. But mine, I am adivised, could not. Good luck...!

 

Update!
So after replacing the BMS that didn't fix the issue ,got to the alternator l,ocal repair shop took off and repaired and put back for $500. Alternator was full of oil.
Now everything is running like it should but the output voltage started dropping below 14 as low as 12.4 if the car is idling and I put high load on like heated seats climate control fully on and lights on. Is this normal or is the alternator running weaker than it should? When the RPMs go up the alternator goes over 14.

 

FWIW my Alternator could not be repaired as I was told it had shorted due to the oil. You can get a new DENSO alternator from the link I posted for $240 or so.

Did you find the source of the oil leak and repair it?

 

Source is the valve cover and no not repsired yet is it appears it's a very expensive procedure. So far everything is running good it's just drop a voltage at idle that I wasn't sure if it was normal but otherwise as soon as the RPM goes up voltage is passed 14 which is good

 

Hard to say but I have a volt meter in the console so I watch the car's voltage regularly. With the BMS the voltage is all over the place! Goes to 15+ VDC for a bit after starting and then comes back down to 12-13 VDC. But does vary quite a bit more than I would have thought.
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Yes getting to the valve covers, as I had to do, can be very expensive, but if you don't stop that leak your alternator will / may well get fried again. I know San Diego pretty well. Go see Michel at Exclusive motors up near Miramar, (I know he works Mercedes) but he knows all the best indies and may well know someone who can do it for you for less than a days labor. Feel free to PM me for more info. IMHO, you gotta get those valve cover gaskets replaced and use that same opportunity to change the crappy plastic coolant pipes to metal, and perhaps put in a new DELSO alternator with lifetime warranty from FCP Euro for 230. https://www.fcpeuro.com/products/lan...1g#description

 

Thanks for the tips , I'll check with him! I need other things I like cooling lines and supercharger coupler as well. Was just hoping to get someone that can do these things for a reasonable price but might have to tackle myself instead, just got to find the time.
By the way if you haven't tuned your XJ , can help you out! they are a thrill to drive remaped, mine has the crank pulley and tune over 650 horsepower daily driver.

 

no BMS warning = just drive

lots of smart charging systems will command no alternator field at all when the battery is charged up. it confuses a lot of techs when they see 12.something while running but that's how it works

 

That sounds very agreeable. What is your torque up to??

 

Torque numbers are very similar to hp on these , power of good amount south over 600