Mikes xs reg/rectifier getting hot once battery is connected

[BRok13]

1972 xs with pamco , bikes been running fine until the other day came out of work and the battery was almost dead. I noticed the reg/rec was hot to touch while the key was off. Thought it may be the ignition switch tried a generic sportster switch same problem as soon as the battery is hooked up gets hot almost instantly , bad ground ?

 

[retiredgentleman]

I'd suspect the rectifier portion of the rec/reg has a shorted out diode.

Charge your battery so its in a fully charged state. Leave the battery cables disconnected. Connect a VOM to read battery voltage, and note the reading. Unplug the rec/reg. Now connect the battery cables. If the battery voltage does not decrease, you have confirmed that your rectifier is defective. If the battery voltage does decrease, then you have a short circuit in your wiring somewhere??

 

[BRok13]

retiredgentleman , I have the wired for the reg/rec soldered together not connected through a harness. I guess I will just disonnect each one and give it a shot, I know when is does crank over my light does brighten when throttle is given so i know the charging portion is working , my guess is since I have been riding it like this for the last couple months without touching the reg/rec that could possibly made it worse ...

 

[BRok13]

Ok Retiredgentleman when i unhook the fuse going from the battery to the red power line on the reg/rec the reg/rec cools down and doesnt , get hot would that be the because the diode you were speaking about is bad? thanks in advance

 

[jd750ace]

Yes. This is a common type of failure with a regulator/rectifier. The one on my SV650 did the same thing.

 

[retiredgentleman]

For sure, it appears you have a bad rectifier diode.

I recommend you don't buy another combo rec/reg from Mikesxs. For your 1972 with a stock alternator, its better to use a separate rectifier and a separate regulator. With individual devices, its easier and cheaper to replace if one fails.

You can buy a NOS VR-115 automotive regulator (E-bay). You can buy a 3 phase rectifier, also from E-bay. Use the Google custom Search in the upper left corner. Lots of threads telling you how to do this.

 

[BRok13]

Ok I had a couple loose connections and fixed those , its not super hot to the touch
When off anymore but is still a little warm , I'm trying every route possible
Since I just bought this reg/rec back in march . Gonna leave it connected and check
The voltage in a while and see if its still draining , it shouldn't be warm sitting though
Should it?

 

[BRok13]

Also I notice some of the diagrams for miles reg rec have a seperate wire coming off the green wire to a ground , I didn't do that could that be my problem ?

 

[retiredgentleman]

Also I notice some of the diagrams for miles reg rec have a seperate wire coming off the green wire to a ground , I didn't do that could that be my problem ?

Where I used to work, we had a saying," If all else fails, follow the instructions".

Here's a pic of the wiring instructions from Mikesxs. You should have those same instructions, and you should have followed them.

Yes, the green wire from Mikesxs rec/reg needs to go to a good ground. Actually its supposed to connect to the right (inner) brush on the alternator, which is grounded to the alternator steel frame.

With key off, there should be zero heat coming from the rec/reg.

 

[BRok13]

Alright well everything is hooked up correctly and with the test light and the key switch off nothing is getting power to it with the key switch on the brushes and everything is getting power so it seems to be working correctly and its charging just still getting hot when sitting, so it must be the diode ... What would cause that to go bad ?

 

[jd750ace]

Diodes and capacitors are all made in China now and the quality is highly random. I have aircraft parts that cost tens of thousands of dollars laying down on shitty diodes and capacitors.
Probably more components than that, but I've had plenty of experience with both lately.