Quote:
Originally Posted by Discseven
Percy... I had same odd tach readings when my alt was dying. And same ability to charge battery and start car but to no lasting avail. Way to diagnosis alternator vs voltage regulator = volt reg basically stops alt from OVERCHARGING system. So, if system is not charging sufficiently to over charge... it's alternator problem. If system is overcharging... it's voltage regulator not doing its' job.
Lack of charging could possibly be ground strap connecting engine/trans to chassis coming loose. It's a long shot but worth checking before anything else. Not 100% sure where strap is on your '88. Typically it's on right side of trans connected to bulkhead of car next to where shifter linkage enters/exits car.
Replaced my alt with this BOSCH rebuilt alt for $300 (after handing over my core.) Voltage reg is internal to this--VALEO. Will suggest return of old core and buy of new part is more economical to do locally as compared to shipping these parts due to weight. When alt was out of fan housing, had fan housing lathed so alt would fit into/out of housing with perfect slip fit.
ORANGE TAG WARNING NOTICE: when installing alt, battery should be disconnected and
"battery should be fully charged or alt may be damaged."
Another "old wives tale" that should have been put out to pasture many years ago.
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Alternators have a built-in self limiting current flow, an 80A alternator will self-limit to ~80A, but certainly no more than 100A. Once the stator(s) magnetic field created by the generated, output, current flow rises high enough to overcome the rotor magnetic field the limit is reached.
The alternator cannot produce this level of current except with engine RPM elevated well above idle in which case the cooling airflow is sufficient to cool the diodes and VR.
The diodes and VR are designed, specified, to provide and sustain the maximum rated current flow provided sufficient cooling airflow is available.
Over my MANY years of driving I have jump started many cars with a dead battery, many of my own. The Alternator CANNOT be damaged simply recharging a dead battery.
On the other hand the alternator/VR combination WILL/CAN damage a battery, boil the electrolyte away, if it is used to recharge the dead battery time after time, repetitively.
Your VR has no method of sensing the battery charge level, SOC, it will "signal" the alternator to put out the maximum current flow possible given the engine RPM limiting factor, OR a voltage maximum of ~14 volts.
https://books.google.com/books?id=kXcNH5XwNHIC&pg=PA193&lpg=PA193&dq=current+self-limiting+alternator&source=bl&ots=h4XScpjqC4&sig=qa3P7pSUfqXOopfyqTWMXt_EboY&hl=en&sa=X&ei=H-CqVLKsA8SuogTWiIH4Cw&ved=0CDAQ6AEwAzgK#v=onepage&q=current%20self-limiting%20alternator&f=false