1979 GS550N regulator/ rectifier or rectifier only?

[Vloukole]

Hi guys

Can somebody please help me identify if this unit with part number DE3804, is a reg/rec or just a rec? I seem to be getting mixed answers online.
I can not find a regulator unit on the bike.
I?m thinking it is a rec only, because I tested the voltage at the battery at 5k rpm. It read 16.5 volts.
Headlight switch was off and headlight unplug.

Thank you

[tom203]

Can?t help identifying the pn#?..but I?d guess that?s a replacement combo rectifier / regulator unit. I?m sure you read all the stuff about shunt vs series r/r units. At a minimum , I?d opt for a used Honda r/r from around 1980,, like a SH-2xx series?..your stator seems good, but you won?t really know till it?s loaded!

[Rich82GS750TZ]

16.5v is way too high and will cook your battery. A quick google leads me to be believe that the DE3804 is a Reg/Rec off of a late '70s Yamaha. Plenty of stories on here about how to fix the GS charging system for good. After doing it myself, don't know why anyone would do anything but install a SH775, clean up the grounds to a single point, and eliminate the headlamp loop.

[Vloukole]

Thanks for the response.
I will be upgrading my reg/rec and bypassing the headlight.
Do you think I got the 16v at the battery because it was basically a no-load test as described in the manual?

[Rich82GS750TZ]

I can't read that, but I'm thinking that a properly functioning regulator would never let the volts going to the battery get above the high 14's, though I am, admittedly, an electrical noob.

[Grimly]

Thanks for the response.
I will be upgrading my reg/rec and bypassing the headlight.
Do you think I got the 16v at the battery because it was basically a no-load test as described in the manual?

Nah, it was 16v because something's busted. Shouldn't ever exceed 14.8 totally max, and that would be pushing the envelope.

[Gorminrider]

+1 .It's too small to be both. Definitely funky stuff in the hestory somewhere...
yes,Rich nailed it. That tiny thing is a "Yamaha XS400 Stanley DE3804 Rectifier only"
Funnily enough it turned up here:

https://www.thegsresources.com/_forum/showthread.php?134690-Rectifier-Regulator-replacement-list

[hank2]

I don't know if this is any help but looking at the parts fiche for a '79 GS550E it does have a separate regulator and rectifier. Here's a link to a parts seller page showing the '79 parts but not where they are installed. Image is copywrited so just a link. Could the box right above the Yamaha rectifier be the regulator? #8 is regulator, #17 is rectifier.

https://www.partzilla.com/catalog/su...50e/electrical

Best to replace both with series type R/R combo as others mentioned, but if you want to get just a bike regulator, the original BMW airheads used separate units also. Euro Moto Electrics (EME) has small regulator only units for about $20.

https://www.euromotoelectrics.com/category-s/1680.htm

Near bottom of page.

[Vloukole]

I am going to replace it with a R/R unit to be safe.
Thank you all

[Vloukole]

Update:

I replaced the rectifier with a new R/R unit. Charging 14.8v at 5000rpm.
Is it fine if I just unplugged the headlight loop?

[Gorminrider]

Update:

I replaced the rectifier with a new R/R unit. Charging 14.8v at 5000rpm.
Is it fine if I just unplugged the headlight loop?

Your new R/R is working fine. You can either leave "the loop" alone or bypass it where the stator connects. It is very simple. If you just "unplug it" you will lose one third of your stator's output.

Look closely at your wiring diagram and search here for the multitude of threads about "stator loop"