High Voltage problem [SOLVED!]

[Trot]

Howdy,

A couple weeks ago I saw my volt gauge reading high voltage while riding, so I got it home to check it. Since that reference gauge is just an aftermarket kuyakyn I installed for reference, I put my actual voltmeter to the battery. At idle it was reading 13.2v, and at around 4-5000 RPM was a steady 15.7-16+ volts.

So since I've seen fried regulator/retifiers before, I ordered a replacement. Same problem. Ordered another, still the same. Replaced the battery since it's old (old enough I don't remember when I last replaced it), still same problem.

Could it be the alternator itself? The system is pretty simple: battery, alternator, regulator/rectifier. Usually 99 times out of 100 it's a bad R/R for voltage problems but I've ruled that out, and the alternator is obviously pumping out plenty of power to the R/R to meter out to the battery.

I'm getting mildly frustrated at this point, but before I get on eBay and start buying a new frankenstein's monster of an electrical system replacement canibalized parts I wanted to ask here. None of my usual motorcycle buddies know any more than I do regarding electrical problems. I'm usually the one they come to when they have power gremlins!

Thanks in advance!

It's on a 1991 Nighthawk 750

 

[brettp]

I've seen discussions here where people buy multiple R/Rs that fail because they were Chinese crap or simply poor quality.
The alternator/generator put out way more AC voltage than 15V, so it is unlikely it is overpowering the R/R. The R/R converts all AC power to DC and dumps the excess. I think the name of a good place for R/Rs is ricksmotorsportelectrics.com or RMStator

 

[Trot]

I've seen discussions here where people buy multiple R/Rs that fail because they were Chinese crap or simply poor quality.
The alternator/generator put out way more AC voltage than 15V, so it is unlikely it is overpowering the R/R. The R/R converts all AC power to DC and dumps the excess. I think the name of a good place for R/Rs is ricksmotorsportelectrics.com or RMStator

One of the two R/R's I got was a Rick's one. I also just did a check on the alternator and all the resistance readings seem within range, though right on the higher edge of the limit, but still within.

I agree 100% with you, the AC voltage should not be overpowering the R/R.

 

[Trot]

Ok everyone, I think I found the problem. The voltage signal going to the R/R must have had too much resistance from an old ignition switch (plus a kill switch I'd also run in line with it). So basically the R/R was doing it's job, just running off of a low reading and pumping out too much voltage. I found a video explaining the idea, which helped me think to trace my wiring and isolate where the problem (hopefully) was. Thankfully it doesn't seem to be a short somewhere in the harness or anything, just a bad switch or old wiring/connections.

After pulling it all apart, cleaning the wires, making new connections, and running a temp new universal car ignition switch straight to the ignition wires (left out the kill switch circuit) it was reading 14.7v at the terminals at 5000 RPM, so inside the 13-15v range the manual specifies.

Hopefully this helps someone else out in the future!

 

[brettp]

Outstanding! Thanks for sharing the solution! That was a great video and explanation. I assumed all R/Rs were programmed to charge at a certain level regardless of the feed voltage. Come to find out, if that feed wire has an issue in the circuit, it will look like a bad RR but it is fine.