Originally Posted by TRBO2NR
So do the Rectifiers actually go bad? Or do they just cause the battery to go bad when they overheat? The reason I ask is, if I replace the battery and make a heat shield would that be fine? Orrrr would the rectifier be bad so even with a heat shield it would wreck the battery?
I'm sure regulator/rectifiers can and do go bad but I'd be more inclined to suspect that maybe it's just your battery. Even properly maintained batteries have a limited service life, and it can be damaged if it has drained for a long time. Here's a quote from the service manual:
Battery voltage may recover after battery charging, but under heavy load, battery voltage will drop quickly and eventually die out. For this reason, the charging system is often suspected as the problem. Battery overcharge often results from problems in the battery itself, which may appear to be an overcharging symptom. If one of the battery cells is shorted and battery voltage does not increase, the regulator/rectifier supplies excess voltage to the battery. Under these conditions the electrolyte level goes down quickly.
I installed the new regulator/rectifier last night and rode my RR this morning to work but have not had a chance to do any diagnostics yet. No problems so far but I think in my case that I need a new battery. Right after I bought my RR used a year ago the battery went dead. I just had it charged back and went on my merry way but I never have done any other maintenance on it.
Here's some things you can check (from the service manual):
Battery: A fully charged battery will measure 13.0v-13.2v, undercharged will show less than 12.3v.
Charging voltage (regulated voltage):
Run the engine to 5000rpm and measure across the battery. It should show between 13.2v and 15.5v.
Alternator charging coil:
At the regulator/rectifier disconnect the 3-pin connector (it has 3 yellow wires). Measure the resistance between the 3 yellow wires, it should measure 0.1-1.0 ohms. Check the continuity between each yellow wire and ground, there should be NO continuity. If the resistance is way off or there is any continuity to ground then the alternator stator may need to be replaced.
Disconnect the two connectors at the regulator/rectifier. One is a 3-pin (3 yellow wires), the other a 4-pin (2 red +, 2 green - (ground) wires). Check for any loose contacts or corroded terminals. If the regulated voltage reading is out of spec then measure the voltage between terminals on the connectors (wire harness side, not the regulator side) as follows: a)battery voltage should appear between the red + and green - (ground) wires b)resistance between each yellow wire terminal should be 0.1-1.0 ohms c)continuity should exist between green wires and ground.
If all components of the charging system are normal and there are not loose connections at the regulator/rectifier then the regulator/rectifier may be bad.