Was it a big diode or a little one? The big diodes are arranged as a 3 phase full wave bridge configuration. They usually have some heat sink fins on them. They dont look like a classic diode. More of a power rectifier assembly. They are impossible to check individually without disconnecting the stator wires. If one diode in the assembly is bad, it cannot usually be replaced as a single diode.

There is also several small diodes which provide power to the voltage regulator.

So which diode (assembly) was it?

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I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k