Electrical help needed

[old smokey]

My GTR has an electrical issue I could use suggestions on.
With it running and the key in position 1, I'm reading about 13.0 - 13.2 volts across the battery terminals.
If I press the rear brake for the light to come on, it drops to the low 11s.
Once I turn the key to position 2 with the headlight on, it goes down to the mid 10 volt range. If I add the back brake light to that it's in the upper 9 volt range.
The headlight switch is still gummy and only takes a little wiggling to make the headlight not work.
Could it be the headlight switch? Or the diode? The ignition switch? Or a bad ground in the lighting circuit or....?

[OldSwartout]

Could it be the headlight switch? Or the diode? The ignition switch? Or a bad ground in the lighting circuit or....?

Yes.....   

[BSOrion]

FYI, there were significant improvements to my RS-200's lighting just by a thorough go-through of all grounding points I could find.  If they looked at all corroded, I pulled them apart and checked for frayed wires then cleaned and lubed em' up with WD-40 before re-securing them.  It seems that most of my problems with electrical have come down to grounding.

If it makes you feel any better, I do most of my work in the hot, humid open air of Alexandria, VA as I'm currently without a garage.  But I do have a workshop that I managed to squeeze into the laundry room last night.  It measures 3' x 4' which means I could fit my engine or a wheel off my bike if needed   Good times!

Orion

[rocketman]

Hi,Smokey! Patience and the process of elimination will be your best friend on this one. I hope others will weigh in for you with some of what they have found to be thier particular problems solved in this regard. All connections are imediately suspect and I don't like what your saying about your switch. That said,grounds are the culprit of many a mystery electrical problem,along with frayed braided wires at connection points (wire ends and connectors),they can reduce the amperage ,etc. Bad switch contacts too. Look real good at all snap or crimp type connectors that may have been used in repairs as they are likely to give up eventually,especially if they are not done correctly and heat shrink wrapped. personally,I try to solder all repairs and ends/connectors. You can check the switches reliability by eliminating it and testing the circuits and or the switch individually. Be carefull that you don't cross anything up and know thru schematic,etc.which circuits are which before you start. Motorcyclists like to keep thier bikes clean,which means constant washings. Trouble...real trouble with a pressure washer. Have you checked things for water or corrosion,(ie generator,switches,etc.)?  Possible the gen. just isn't keeping up.  Mark.

[old smokey]

I guess I gave OldSwartout too many options.
I'll start with buying a can of contact spray cleaner to use on the headlight switch and ignition switch.
I remembered (barely) thinking that when it was parked in '86 that it had a charging problem.
My first tests this season were with the headlight off, which seems fine.
I remember some troubleshooting guidelines for a 175 on here, I'll have to see if the same applies on a GTR.

[rocketman]

I think Karls havin' a little fun with you. In the interim,I got to wondering if your getting a voltage increase as the RPM's rise. Sounds like your switches need a little attention anyway,and you got to start somewhere...good a place as any. Good luck,Mark.

[old smokey]

Oh yea, I knew what Karl meant...
I saw 2 leads on the rectifier had some corrosion, so those are cleaned now.
Tomorrow I'll get the spray and do some testing before the mosquitos come out.

[Toystoretom]

Just to add to the confusion    you can do some basic stuff first.

The good news is that GTR's have very simple electrical systems. A battery, an alternator, some coils, some lights and switches.

Check your battery first. Disconnect it from the bike and measure the volts across the terminals. It should be about 12.2 to 12.4 volts if the battery is healthy. Higher than that is great, lower than that isn't good. You can do a simple load test on it by keeping your meter connected to it and hooking up a brake light bulb to it (if you have a bulb socket this would be easy, or just strip some wires and make a harness, it doesn't have to be fancy, it just has to work. You could even hold the wires to the bulb while watching the meter.) If the volts crash with just this small load on it, your battery is toast.

With your bike running the only thing drawing current is the coils. If you turn on lights you increase the load. At an idle, your battery shoulders this load, so if your battery is weak, your volts will drop. I don't know when the alternator really starts to kick in but I'll bet it is around 1500 rpm's, or maybe higher. Possibly re-test your readings with an assistant holding the throttle open while trying to maintain 2000 rpm's and see if the alternator is keeping up with the loads.

All the above advice about dirty connections and grounds and switches is great. Clean that stuff up and your bike will be more reliable.

When you look at electrical stuff just study the circuit, see what it does and how it works. Run some tests, you can find it. Your DVOM is your buddy.

You can do voltage drop tests across connections. This proves you have a bad connection and takes the guesswork out of it. Clean the connection and retest. A bad connection is a point of high resistance and may create heat and put a large draw on the electrical system. Google "voltage drop test" if you don't know how to do it.

If you don't have a DVOM buy one, you can get a nice one at Wally World for $20. Buy some wire and some alligator clips (get those at Radio Shack) and make up some test jumper cables. Buy some "T" pins to probe wires and connectors (to hook your jumper cables to and attach those to your meter leads.) "T" pins can be had at beauty supply stores and are also known as wig pins. If you are bald and ask the girl behind the counter where the wig pins are at she will laugh at you, so be prepared. You must do this to fix your GTR.....

[old smokey]

photo of rectifier taken from left side of bike, towards the right is the back of the bike.
I did the light bulb test described in the manual.
The bulb did light up so that says the rectifier is bad.
However when I switched polarity of the 12v leads, the bulb didn't light.
I thought maybe the bulb would light when tested both ways if the rectifier was bad.
So before I contact Richard for a new rectifier, can someone verify that the negative lead to the rectifier for normal operation goes to the back of the rectifier and the positive lead is towards the front of the bike?

[old smokey]

I re-read Karls advice for testing in the 175 category. It seems like the first test I did would be good results for the rectifier, but I need to head out to the garage to test the 3 other ways he listed.

[old smokey]

Testing the rectifier by the 4 ways Karl described my rectifier tests good.
I checked a few connections, spray cleaned the headlight and key switches and ran it for another voltage check.
Measuring across the battery terminals, while in key 1 position at 3000 rpm I'm getting about 13.8-14.0 volts. Then when I click over to key position 2 (headlight on) I'm getting 12.0 volts at 3000 rpm.
The charts in the service manual show that each of those values should be about 2 volts higher.

Which leads would I measure the voltage output of the dynamo itself?

And is the voltage regulator something that can adjusted?

[BSOrion]

Old Smokey,

If the harness is the same as on the 200, you'll have a brown, yellow, and blue wire.  Those are the three outputs of the 3-phase dynamo.  If I remember correctly, I've got about 5-7 AC volts coming from each of the 3-wires on mine.  If the wiring is not the same, just see if you have AC volts coming from any of them.  Black and white wires will typically go to the coils so that should help narrow it down a bit.

Best of luck, Orion

[reed]

Old smokey
If your rectifier checked out and your wiring is good it must be in dynamo.
Look at your wiring diagram check output on brown yellow white blue.
Yes you can adjust the regulator usually its when its over charging
The part no of the dynamo assy is 1703-9000.
Thanks.
Reed.

[old smokey]

thanks for the input. I hope to do some testing one of these weeknights.

[old smokey]

The voltage regulator definitely suffered from days in an unheated garage, so I sanded the points clean and knocked rust off the other parts.
I increased the gap on the points. Here's where I left it.
Running at about 3000 rpm with the headlight on, I read 5.0 volts on the white lead at the rectifier.
The blue lead reads about 5.8 volts and the yellow lead had about 6.0 volts as measured where they connect to the rectifier.
Measuring voltage across the battery terminals I get about 14.7 volts when the headlight is OFF at 3000 rpm.
With the headlight ON I read about 12.0 volts at 3000 rpm.
I see from my Aug 21 post that the voltage across the battery terminals didn't change any after messing with the voltage regulator.


Although reading the numbers from my original post they have gone up from the combined things I've cleaned.
The large voltage drop when the brake light was applied seemed to be the blue lead from the brake switch not being fully seated in the harness connection.
Thank goodness it's easy to pull the tank off these things.

[reed]

Old smokey
I still think its in your dynamo assy.
My output readings are higher on my dynamo
than yours!
Thanks.
Reed.

[BSOrion]

Steve, I'm curious if the 350GTR is similar to my 200 where only two of the wires carrying AC go directly to the rectifier and the third goes to the switch where it is only engaged when the main switch is turned to the light position.  If so, it's possible that Old Smokey isn't getting the third AC input to the rectifier due to a failing switch.  I suppose he could try a bypass to test.

Orion

[OldSwartout]

You're right.  The brown wire from the dynamo goes to the switch, then comes back to the rectifier as a white wire.  That circuit is used when the lights are on, just like the 175/200.  Old Smokey can try pulling the brown wire apart at a connector somewhere and use a jumper wire to connect directly to the white terminal at the rectifier.

Another possibility is that the headlight has a different bulb than stock in it.  It is supposed to be a 35/35W bulb.  However, I believe a 65/65W H4 will fit.  Someone may have put a different bulb in it to get more light, but the alternator won't keep up with that except at very high RPM.

[reed]

Karl
I agree with you but i would like to know the output of the brown before the switch!
Because if the output is low on the brown before the switch there is your problem.
Thanks.
Reed.

[old smokey]

That's plenty of more good troubleshooting ideas.
I think the headlight bulb is an original style, I think it says Hirose or Mirose 35W on it.
Next chance I get some garage time I'll try to find a spot to check the dynamo output on the brown wire before the switch where it changes to blue. Thanks!