Alternator internal regulator replacement
Hello auto electric experts out there. I've got a '98 SLE (Yes there was an SLE in 98, basically the same as the SE with a couple of added options as standard. Not many badged as SLE that year.)
Just got the car a month ago with 84k on it. I noticed it had a Bosch alternator while I was doing plugs and wires. Previous owner must have replaced the OEM Delco.
Anyway, the voltmeter is fluctuating when the car gets hot, even with little electrical load. Worse at idle, but noticeable while driving. Voltmeter is ok, the lights also noticeably become brighter and dimmer following the voltmeter. Never goes above 14 or below the area of the red mark. An auto mechanic friend of mine tightened all of the connections on the alternator and the battery. This did not help. He feels the Bosch probably has a bad internal regulator (heat sensitive) and the diodes are most likely ok.
He is suggesting removing the alternator and replacing the internal regulator with one available from Advanced Auto (about $43) as opposed to a remanufactured Delco Alternator at about $150. Since the Bosch alternator is not very old, this makes some savings sense to me.
However, could it be something else like a diode breaking down in the heat? Alternator output seems ok under high electrical loads, although this has not been checked professionally. I don't want to take a $43 gamble if it might be diodes or something else. Rather spend the $150 and be done with it. Advise? Thanks