New SH-775 R/R, charging voltage higher than 16VDC

[Elijah Johnston]

Good afternoon everyone,
Ran into an odd issue with my partner's 1980 GS850GL.
Bought the bike, overhauled the electrical system, cleaned all contacts, fuse box, ignition, and virtually every trouble spot I could read about on the forums.
Got rid of the headlight/loop for the third stator leg, ran through all tests from the Stator Papers, determined I had a bad R/R and replaced it with a new, authentic SH-775. It has the characteristic stainless steel back, the casting lobes across the front of the fins, and the Shindingen part numbers, I have to no reason to doubt its authenticity.

Bike ran fine for a while afterwards, the charging system seemed more than capable of supporting heated grips, and a few other 'farkles,' but the last couple times I fired it up, the idle voltage spiked past 15VDC at the battery, and hit 16VDC at 4k RPM before I shut it off.

What I can find on the forums indicates that this is a result of the R/R not doing its job and regulating the electricity, I find it odd that an SH-775 with all its touted benefits would fail in basic regulation.
Is there a connection somewhere that is a likely culprit?
Something I haven't checked?
I am not at this time running a SPG, if I were to do so would that help?
Voltage drops on positive and negative R/R leads are both less than .25 VDC at 5k RPM.
Am I missing something, or did I get a dud unit?
Any help is very appreciated.

[gs11ezrydr]

What is the condition of the battery? Was it fully charged before R/R was installed? Could effect charging output..Possibly trying to charge the battery instead of maintaining it.. 16VDC should be just about maxed out...

[Elijah Johnston]

Howdy, thanks for the reply. The battery is a new AGM 12V battery, rated for 220 CCA.
It was fully charged, reading 12.8 this afternoon. I installed the SH-775 a few months ago, and the bike has been running great since then. The highest voltage I've seen is 15.1VDC at the battery posts, at cruising speed (I have a voltage monitor installed.)
My understanding at this point is that it could be a grounding issue of the R/R... so my next mitigation attempt will be installing a single point ground setup.

[Nessism]

Before going through all the wire rerouting necessary to execute a single point ground scheme I'd jumper your R/R ground straight to the battery and see if that fixes the situation.

[Elijah Johnston]

Thanks Ed, I was just reading through Jim's articles on the benefits of SPG, I'm about halfway through wrapping my head around it.
The voltage has always seemed a little high when running the SH-775, I may not have understood the importance of the ground connection from the R/R.
If it's not too much trouble, can you pass the links detailing exactly how to set up the SPG scheme? I'm sure posplayr has written something to the effect, but it would also probably take several hours for me to extract the tidbits.
Thanks for recommending the R/R negative test.

[tom203]

“Am I missing something, or did I get a dud unit?”
A year ago, I tested a seadoo sh-775 (appeared genuine/new)that I’d acquired by swapping it for the Polaris sh-775 on my bike. The voltage was 1.5 volt higher than the Polaris unit ...actually hit 16 volts @4k rpm. I ran it for an hour out of morbid curiosity...when I swapped back to the Polaris unit, voltages dropped to normal. All connections were the same.Sadly my newish battery suffered from this brief testing..it was never able to hold a decent charge again. I think the seadoo was a dud.....yours sounds similar

[Nessism]

Sorry, but I've never used Jim's single point ground scheme on any of my bikes. Below is a simplified diagram on how to hook up the unit.


SH775 Install by nessism, on Flickr

[Grimly]

Oh well, it looks like the reliability record has been tarnished.
In percentage terms it must be pretty low, given the thousands that have been re-purposed.
However, I'd not be at all surprised that the duds that show up have been put back on to the market by stock acquirers who don't actually test them.
These may have been returns under warranty that landed up back at a dealer's back shelf and were never meant to be re-sold.
I'd still be pretty confident buying from somebody like powersportsnation who checks the output before stripping the vehicle.

[Nessism]

I've tested in the neighborhood of two dozen used SH775's and haven't witnessed a dud yet. And a few of those were Seadoo units. The only thing I've noticed during testing is that if my battery was low the max output was low, about 14.0 VDC. After charging the battery the charging voltage increases to about 14.4 or 14.5 VDC.

[Brendan W]

Have you compared the monitor readings with a multimeter, just to eliminate a possibility.

[Elijah Johnston]

Good morning everyone, thanks for the replies.
Yes, I did confirm the reading with my multimeter, it was within .05 of the monitor. First step this morning once I get some coffee down is going to be directly connecting that R/R negative to the negative battery post, and seeing if my reading changes. If it does, that tells me I need to rethink my ground setup.
A takeaway from (Jim's) GS Stator contest thread is that there may be disadvantages of connecting the R/R straight to the battery as a permanent setup, as the theoretical current return path is the negative lead of the R/R. Has anyone really messed with this, or is this theoretical at this point?

If it turns out I just have a bad unit, I have another new SH-775 in my shop, I just finished installing wires and potting them in with Dow 748.
That way I can isolate the issue to the wiring, or the unit.

[tom203]

Have you stumbled across this thread?

http://www.thegsresources.com/_forum/showthread.php?152769-GS-Charging-System-Health&p=1138898#post1138898

[Nessism]

If it turns out I just have a bad unit, I have another new SH-775 in my shop, I just finished installing wires and potting them in with Dow 748.

I've snatched up a couple tube of Dow DOSIL 3145 and use it to pot the cavity after installing loose spade terminal wires on a few SH775's. In addition to being cheap, it allows the wires to turn quickly as they exit the R/R in the case of a tight fit on the bike.

[Elijah Johnston]

Hey everyone, thanks again for the help and suggestions. Ed, you were right on the money about it being a bad R/R return. I really don't like having more than one lead to my battery, but the R/R negative might just stay there for now, despite my thinking of it as a bandaid until I create a SPG for it.
So problem solved there! Fired it up, raised the RPM, saw 14.4 to 14.7 at 2500, raised it all the way up to 6k RPM for good measure, highest voltage I saw was 14.8, gave me the warm and fuzzies across the board.
Ed, I think I saw your mentioning using the Dow 3145 a while ago in another thread, that's where I got the idea of potting the SH775 connections past the spades. Unfortunately not all of us are fortunate enough to work in the aerospace industry, I think I found a mention in the same thread about using Dow 748, a RTV sealant that doesn't emit the aecetic acid harmful to wire connections.
In any case, the R/R seems fine now, the negative lead is bolted fast straight to the battery, and we'll continue to monitor.
Next project: installing a relay mod for the horn.

[salty_monk]

If you're putting a relay in for the horn... you should consider the headlight & the feed to the coils if you didn't already. SPG is pretty easy & can be done in a partial format. Pick a point on the frame where you have a convenient bolt, make it longer & move every ground within reach to it & then put a nice big one back to the battery..... I use an airbox fixing for mine as I don't have an airbox.

It won't hurt anything having it going back to the battery though in my experience.