wiring melted to rectifier on 79 special

[sbtm]

This happened a few years ago, so I can't supply the details of what happened, but here is the jist. I have a 79 special (all stock) that's has some melted wiring. The black wire from the rectifier (I am assuming this is the right part, mounted on the underside of the stock battery box) is melted all the way up to where is is joined with a couple other black wires, near the junction to the fusebox.

The bike still runs (I started it last spring but decided I didn't have the time or patience to dig in) but what is the cause of the problem? Bad rectifier I am assuming, bit I'd like to make sure.

Cheers,
Dylan

 

[sbtm]

After a little more searching i figured I'd test the rectifier and it seems to test good. here are my results:

I used the Diode test setting on my multimeter, black probe (b) on the COM port , red probe (r) on the other. these combinations are the only ones with current flow. reversing the polarity shows no flow, meaning the diode is in fact working.

b - r Voltage drop
R 1 .536
R 2 .536
R 3 .535
4 G .539
5 G .535
6 G .535
R G 1.187

Time to test the voltage regulator i suppose?

 

[retiredgentleman]

Welcome to the forum;

Wiring problems are just part of owning these classic bikes. You are going to have to spend some time, disconnecting the connectors on the bike and cleaning the bullet connectors so they are bright and shiney.

Here's a few recommendations:

Replace the 4 position fuse panel (glass fuses) with automotive blade type fuse holders. Solder all connections and use heat shrink insulation.

Replace the old rectifier (hiding under the battery box) with 2 new bridge rectifiers.

Replace the old relay type regulator with a NOS solid state regulator that was used on 1970's autos.

 

[sbtm]

Thanks retiredgentleman,

I read a post earlier about replacing the rectifier, sounds like a good idea.

Come to think of it, my main fuse holder broke when i last rode the bike, it would cut out intermittently, id have to roll over to the side of the road and fumble with the fusebox. Could that have been the cause of the melted wire?
I rewired it with an inline blade fuse holder, but the other 3 fuses are still the old glass type.

 

[jayel]

the black wires are the grounds if they melted I would think you should check frame grounds (loose engine bolts), battery to frame ground, battery box is rubber mounted so it is not a reliable ground point.... all connector(s) clean and tight

 

[XSLeo]

The way you are trying to test the rectifier isn't the proper procedure. To test the rectifier you test at the plug. Meter on the Diode check. Touch the red probe to the red wire, touch the black probe to the three white wires. Now reverse the probes.
Do the same with the black wire.
You should get about the opposite reading on the second test as the first. As long as the high readings one way througfh the diode is 10 times as much or more than the low. The good one I have reads about .600 one way and infinite the other way.
The Clymer book covers this test on page 39.
Leo