I am now looking to eliminate my air pump and replace that with
another alternator; so far my Bosch alternator seems different from
the GM that Kirby recommends.
Well, yeah. The OEM Bosch fits in the OEM location. A GM CS130 fits
better in the air pump location.
I am also concerned about replacing the
flat groved belt with the V belt.
Part of the point is using the V belt, because the air pump serves as
the belt tensioner for the A/C compressor belt. The OEM alt serves
only as a belt tensioner for itself. By installing a CS130 in place
of the air pump, you eliminate one belt – in the case of later Bosch
alt cars, the ribbed belt – and you eliminate any and all drive off
the crank damper. The CS130 in the air pump location is driven off
the pulley, not the damper; the damper shouldn’t ever fail again.
I do, however, recommend using a fairly large V-belt pulley on the
CS130. For one thing, the A/C compressor uses a thick V belt, not a
thin one. If you buy a suitable pulley for the CS130 (any alt shop
should be able to provide one), it’s a bit larger in diameter than
you are accustomed to seeing on an alt. Doesn’t hurt anything; the
CS130 turns a bit slower than it would with a conventional size
pulley, but it charges so well anyway that it’s not a problem. It
also prevents overrevving the alt at redline.
Bosch alt owners should note that the Bosch alt is 115 amp while the
CS130 is only 105 amp. I don’t believe this would pose a problem,
since the earlier Lucas alt was only 75 amp and I don’t believe the
XJ-S gained any significant electrical loads when the Bosch alt was
introduced. With the notable exception of the convertible top, of
course, but that’s what seems to cause the sheared dampers and
squealing so convertible owners will probably be happy to switch to
The CS130 can be rebuilt to 140 amp, but I wouldn’t recommend it.
The load issues all seem to happen at idle, and increasing the alt
rating usually decreases the output at idle.
There are “heavy duty” rebuild kits for the CS130 that apparently
include a larger rear bearing and a bigger heat sink for the diodes.
That probably would be a good idea, if it’s not too expensive an
option wherever you acquire your alt.
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