Ducati Monster Forum

Hi everyone, it's been a while :)

Bikes s2r 800 2005.

About 6 months ago I replaced regulator rectifier as my OEM one had a burnt diode. I purchased second hand reg/rec, "never used", it's not OEM, could be Chinese for all I know. Worked fine for 6 months until today. Battery was flat and found melted reg/rec connector upon inspection (the 3 yellow wires). I've been riding in a rain every now and then, hoping a wet connector caused that - did a diode test on said reg/rec and it gives me perfect readings on all pins, so I take it as the unit itself is still working fine.

I've decided to replace connectors and keep an eye on it (unless you think it's better to replace the unit?). Now, the 3 yellow wires coming out of reg/rec are the ones with melted connector. Apparently, you connect each wire to one of the yellow wires on the bike, doesn't matter which to which as they all go to the unit where is changed and regulated - is this right? It would make sense as they aren't color coded differently, but I want to make sure because frankly, I've no idea [roll]

I've some spare tyco amp 3 pin connectors. These are waterproof and I think I'm gonna use them.

It doesn't matter which wire goes where. Many people hardwire that connection as it has always been problematic on Ducs.

A quality connector will last longer.

Is the R/R still in the same location (as stock set up)?

Then, it (the location of R/R) is most likely the cause.

R/R doesn't get any air flow in that under seat location.
Including myself, a lot of S4R/S2R owners got stranded because of dead R/R.

(Don't think it won't happen just because it hasn't happened yet.
And when it happens, you may get stranded in unpleasant location at very inconvenient time.)

I'd recommend relocating the R/R.

I took mine and flipped it upside down so the fins face the wheel. But I also dont have a oil catch anymore. Ive always heard of the RR exploding on the newer bikes but im still running the stock RR on my 06 S2R1000 and its been salt water sprayed for gods know how long.

My 1995 M944 on the other hand, the RR was up front by the oil cooler and it ended up catching fire and burned the whole bike down, so ya, YMMV.

If you do not relocate the regulator, even if you do, an upgrade to a MOSFET like https://ricksmotorsportelectrics.com/Hot-Shot-Ducati-Rectifier-Regulator-10_029H

Never thought about turning it upside down.  Great idea!

For you lithium battery folk  https://ricksmotorsportelectrics.com/Rectifier-Regulator-Lithium-Compatible-14_029H

I did the Mosfet upgrade on my S2R using the the Super Mosfet kit from roadstercycle.com and put it pretty much back where it was except I moved it back two inches to make room for the new harness using their mounting plate.  That was two years ago I haven't had any issues from under the seat

Thanks everyone and sorry it took me a while to get back, been busy.

I replaced the connectors on 3 yellow wires, charged the battery and it was fine for a couple of weeks until my battery died again. I've tested stator and reg again and found no issues. Turned out one of the new connectors on said wire snapped (I used spade connectors as didn't have anything else at the time). I'll use bullet connectors now and when it gets warm I'll just solder the wires.

I don't think location of regulator itself has anything to do with it? But even if it's that, there's nowhere to mount it safely so it has to be under the seat.

Right, here's an update. Voltage (checked on battery terminals) doesn't go over 13.5 no matter what rpm.

What I've done:
- replaced the connectors on 3 yellow wires (generator to regulator) and made sure there's a good connection
- 40 amp fuse good
- checked the connection between said fuse and battery, and between fuse and 2 red wires in regulator - all good
- stator isn't grounding
- performed a diode test on 3 yellow wires, same correct readings (both on alternator and regulator side)
- stator AC voltage output is 30 at 2k rpm and 80 at 6k rpm which is what it should be according to the manual

The good news is that the stator works correctly. I think it's safe to say my regulator rectifier is knackered, it doesn't output enough voltage to charge the battery. I'm ordering a new one.

Have you chosen a brand/type?

I highly recommend Rick's Mosfet regulators.

I haven't yet but won't be a cheap one again, thanks I'll check them out :)

FWIW I replaced the R/R in my 96 over 20 years ago with a Rick's, and it's still going strong. Full disclosure, I haven't ridden the bike much for the last 10 years, but it has over 20K on it.

Looks like these are not availible in UK unfortunately so will have to go with something else. In fact, I can't find any decent reg rec here in UK. There are few with mosfet but they're unbranded, and one made by elextrex but people say it outputs too much voltage. I might have to stick with OEM :f

I just found mosfet reg rec made by RMStator. It has good opinions so I think I'm gonna go for it - £115

Rick's won't ship to the UK?

ETA...he'll ship overseas if you use paypal... https://ricksmotorsportelectrics.com/l/rectifier-regulators

Yeah thats correct but it makes no sense to me to order from US, especially now that we left EU, postage delays can be horrendous. Ive recently ordered a zippo lighter insert from US an waited over 2 months. That, plus in case I need to send the item back for warranty, it'd cost me more time and money.

From what Ive read both RMStator and Rick's mosfter regulators are considered top quality units. Ive ordered the former in the end as I couldn't find anything better.