one fine summer day, when my 95riv engine was "awakened",
the instrument panel said “ALTERNATOR”. This was a first.
These generation8 Riv alternators are v powerful and they are expensive.
I have a friend who was head mechanic at a CarMax and because he could get me the maximum
discounts at NAPA/autozone/Advance, we were most respectful.
Upon hearing of this problem my “certified master mechanic” pal announced that the
Riv's charging system is very simple, and he opined that I needed a new alternator.
[ about $150 ] He stated that the alternator itself was the only thing that could go wrong.
further investigation revealed that, even though the instrument panel was illuminating the
ALTERNATOR lamp, it turned out that, at idle, the battery voltage indicated 14.1 volts.
Idling output of 14 volts did not seem like a big crisis, so I got out the trusty Buick Service Manuals,
[ they were 2 volumes, printed by General Motors, and,
the pair was bought on ebay for $100]
they are exactly what Buick mechanics used for reference when working on 8th-gen Rivs back in the day ]
Image – Buick factory service manualshttps://s279.photobucket.com/user/Lmckinley99/media/riv_service_manuals_1416.jpg.html?sort=3&o=5
page from GM manual here:https://s279.photobucket.com/user/Lmckinley99/media/riv_diagnose_alternator_manual.jpeg.html?sort=3&o=0
turns out there is a diagnostic tree for alternator problems. Also, it turns our that the info is
difficult to discover because the Buick service manual calls this device a “generator”, which is a charming anachronism, but not an accurate name for the Riviera's dynamo. Grrrr....
so, I began to figure out this “thermistor”.
Rivs have them. otherwise, only Caddy Eldorados use this part number.
It is a device that senses heat and translates that to varying resistance [ like a temp gauge sending unit ].
this thermistor is no longer available as a GM part. There are none in the GM system now. [year 2014]
image: thermistor collectionhttps://s279.photobucket.com/user/Lmckinley99/media/riv_thermister_collection.jpeg.html?sort=3&o=3
What the thermistor does for a gen8 Riv:
this device is clamped onto the battery positive terminal.
It senses how warm the battery is.
[ when the alternator pushes a lot of amps into the battery, the battery heats up ]
because the battery lives inside the passenger cabin, the system carefully monitors
the rate of charge. A runaway battery would be no fun for the backseat passengers.
The thermistor dials back the charger rate if necc.
The thermistor performs the monitoring mission and it sends temp data to the
alternator, and thus dials back the output of the alternator if the battery gets hot.
if the thermistor fails, the charging system gets confused.
This is what caused this 1995 Riv's “Alternator” lamp to turn itself “on”,
even though the alternator was constantly producing it's maximum output.
The 1995 Riv's thermistor quit sending info to the alternator. This was caused by corrosion
on the pins inside the small white electrical connector leads which send info upline.
[ the corrosion was caused by H2O in the battery well, but that's another story ]
cut off the excellent GM Delphi plastic 2-pin connector and simply re-connected
the wires using high quality squeeze crimp units.
Thermistors were rarely used by GM.
New ones cannot be had.
Whenever I see a gen8 Riv at the junkyards, the back seat gets lifted and the thermistor
is removed. At checkout, the cashier usually has no idea what she is attempting to
put a price on, so the cost is often $2 or, sometimes, free.
The very fact that I have 4 thermistors under the workbench guarantees that i'll never have
a failure of the one which was installed in my RIV at Lake Orion, Michigan in 1995.
moral of this story:
the thermistors in our Rivs are rare and made of a “element” on the periodic table named
As a service to our community, whenever any one of has the opportunity, these devices should
be harvested. [ if anybody requires one of these thermistors, contact me ]
my original alternator continues to hum along after 130,000 miles.
Repairing the 2 wire connections extinguished the ALTERNATOR lamp.
The expensive GM service manuals paid for themselves then and there.
EDIT: the previous (this) post named the offending lamp as "alternator" but that was a mistake. the red lamp which illuminated had no written word description.
it is a little image of a battery located within the left-most circular "idiot light" gauge
and it is located directly above the headlamp switch.