Posted last year about a intermittent charging problem. Sometimes the voltmeter on the dash read the very low and the voltage at the battery was 12.6 while running. Other times a volt meter on dash was 13 and voltage at battery was 13.6. Took it to two mechanics, both times battery was fine they couldn’t see anything wrong. I put the car away for the winter running it every two or three weeks to stop flat spotting while I was driving it battery wasn’t charging but when I took it up to 5000 RPM in second I heard a long screech , and then the alternator was charging. Yesterday starting it up in the garage battery wasn’t charging lots of noise from the engine compartment car was running rough it would almost stop and then kick back up to 7500 RPM then down then up finally a long screech battery was charging engine was running fine belts or pulleys I’m sure, but which ones
Mike,
Your harmonic balancer (crankshaft damper) has failed and it needs to be removed and replaced. This is a common problem. Search the archives for “harmonic balancer squeal” and you will find lots of posts, including some from me when this happened to our 1990 XJ-S convertible.
I removed and replaced it maybe 15 years ago and no problems since.
Paul
Thanks so much for the reply. The crankshaft balancer hopefully is not the crankshaft position sensor because that failed a few months ago stopped me dead in my tracks and I had it replaced.
Mike, I know it sounds silly, but first - you should start from increasing alternator’s drive belt tension.
I have no ide how you’ve started from voltage and ended up on harmonic balancer…
In AJ6 engine for example - that’s the classic drive belt issue.
It seems ok, it seems tensioned, it may be inspected by ehm"professionals", it won’t give any symptoms apart from voltage drop f.eg on cold… The alternator’s worn bearings will give you similar sound…
Get a white out pen and mark the two parts of the harmonic balancer, start the engine and after it screeches turn it off and check the marks, odds on they will not be in line now.
Mike,
The crankshaft damper (a large heavy metal and rubber pulley bolted to the front of the crankshaft) is an entirely different part than the crankshaft position sensor (an inductive sensor on a wire harness that is mounted beneath the crankshaft damper with a cable that runs up the front of the engine to a connector on top of the engine near the A/C compressor).
Paul
XjsBanger,
Mike has a 5.3L V12 XJ-S with a Marelli ignition system and not an AJ6 car. The telltale symptom of the crankshaft failure is the squealing sound it makes sometimes along with charging issues. This is a classic example.
I agree with Robin that drawing a white line on the metal to rubber interface on the crankshft damper will conclusively prove this once the engine is started and the squealing occurs. The white line will no longer be aligned. This is how I determined that the crankshaft damper had failed in our 1990 XJ-S convertible and many others have as documented in the archives.
Paul
Mike,
This is a picture of the front of a 5.3L Jaguar V12 engine with the Marelli ignition. The crankshaft damper is shown circled in blue and the Crankshaft Position Sensor is shown circled in red.
Paul
Hi Paul
Congrats. You are the winner of the
Why is my car intermittently not charging. It is the harmonic balancer.
Thanks for the suggestion
Mike
91 v12 coupe
Mike,
Thank you for posting back with the good news. This adds to the collective knowledge about caring for these cars. I am glad that my posts were helpful in getting your problem fixed.
Paul