Good morning
I just got a 1990 xjs v12. Driving home it died on me and upon diagnosis found the crank sensor damaged by the reflector on the harmonic balancer. Didn’t thought nothing about it when the car started right up. Noticed the battery was dead at the time it died so when had it running again, checked the alternator and found it was charging 11.6 volts. Replaced the alternator and still charging 11.6. When went to check voltage at back of alternator noticed the harmonic balancer broken.
Will this cause the alternator to charge low?
Raymond,
Welcome to Jag-Lovers.
Yes, a failed harmonic balancer will cause problems with battery charging. This is a common problem with the Marelli ignition cars and there are lots of posts about this in the archives and info about it in Kirby Palm’s “Experience in a Book” that can be downloaded for free on Jag-Lovers.
The harmonic balancer in my wife’s 1990 XJ-S convertible started to fail and it squealed on start up sounding like a slipping fan belt. The rubber had separated from the metal in the harmonic balancer causing the squeal. I removed and replaced it myself about 10 years ago or so and haven’t had a problem with it since then.
Paul
Thanks Paul,
Mine is completely separated and even when it does not squeal, it’s free spinning with the belt
Raymond,
The belt to the alternator goes around the harmonic balancer so if it has separated it is not turning the alternator as it should. You may have removed and replaced a perfectly good alternator because the problem was a failing harmonic balancer. Hopefully you didn’t throw the old alternator out.
Paul