Need Help! Yet another Charging Problem! - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 4 (permalink) Old 06-08-2008, 11:43 PM Thread Starter
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Unhappy Need Help! Yet another Charging Problem!

I apologize up front for the long post, but I want to make sure I communicate all of the info I have at this point! Also, I am a newbie at wrenching; in fact this is the first real mechanical project I have undertaken beyond simple maintenance, so I apologize for possibly stating the obvious. I really need help to get this beast back on the road!! Okay, so I identify a bad R/R and stator about 2 weeks after I bought my '89 750. Bummer! I replaced them both. The stator had three posts completely melted and fused. Once finished, I used the Electrosport Fault Finding Guide and everything checked out. No oil leaks, and the new VOM lights up like a Christmas tree, I am truly a happy camper at this point. So I take the bike to work, and about 10 minutes into the ride I notice that the VOM is indicating that the battery is not charging as it was when I started out. Got to work, a 25 mile ride, and the VOM indicates that although charging seems to be happening, I am not getting nearly the voltage I am expecting. On the way home I get about 2 miles from home, while stopped at the gas station, it starts to idle poorly, drops from 1100+ down to around 750 RPM, responds a bit to the throttle, but runs badly with backfiring. Then the engine cuts out completely. $#!& Okay so now I am not a happy campre anymore! I put in a couple of gallons, and the bike starts up, still. running poorly, doesn't seem to be getting any power, backfires a little. Then I notice that the VOM (Kury LED) gets the second greeen light and the bike seems to return to normal. Great, now I can get home; Sucks, cause it looks like I still have a charging problem.

So, back home in the garage, up on the center stand, the seat and the side covers come off, and my multimeter goes on. Initial readings at the battery: @2500 RPM shows 13.5 VDC, and @5000 RPM shows 14.5 VDC exactly as it should. I let the bike idle for a few minutes, then the idle drops again, and the bike cuts out. Now after restarting the bike, the meter shows VDC struggling, only getting 13 and change even up to 5000 rpm; slowly increases, but the bike starts to backfire if I hold the tach at 5000 for a few seconds. So although the readings were absolutely fine when the bike was initially started they seem to be going into the toilet after a few minutes when the bike warms up. So I let it sit for a few minutes. When I restart the bike the readings are back to spec, 13.5 through 14.5 as I increase revs. I notice at this point that when the fan comes on the VDC again starts to struggle. I recharged the battery using my battery tender overnight, and reran the diagnostics on a full charge. Same behavior, all okay at first, fan comes on VDC does not rise significantly revving to 5000. I checked the fan leads and all tested fine.

Back to the drawing board! I disconnected the stator and checked VAC and resistance; all fine. I ran the diode test on the RR; all fine. However, I am out of spec on the RR resistance according to the chart in Clymer's and the Kaw repair manual. Bothers me that some of the readings are out of spec, but I read in the threads that some folks are also getting readings out of spec, and the charging system is operating just fine. Also, it is a brand new RR and the diode tests all check out fine, so I am assuming that the RR is okay. I then start at the top of the fault finding guide, ignoring the initial readings that all is well in my charging system, and discover that I am 2 to three times higher than expected on voltage at the switched power lead on the RR (Brown wire). The guide says that I should be under .2 VDC, I am getting between .5 and .8 volts. The guide says I probably have an open somewhere in the switched power circuit, it also benignly inform me that this is the most difficult fault to identify; just #$^%*@! great! Ther remainder of the tests check out ok.

I studied the wiring diagram, then I disconnected the VOM and the Stebel horn that I installed, and I pulled the accessory, headlight and taillight fuses, to isolate the ignition system and re-took the readings. Everything read well within expected ranges. The fan had no impact at all. Installed accessory fuse, readings still okay. Installed taillight fuse, back to .5 to .8 VDC on switched power. I disconnected all of the turn signals, the lic plate light, and the taillight, and started to take readings after connecting one thing at a time. Everything okay, even when operating the turn signals and hazards, until I plug in the taillight. So I jumped only the brake light without connecting the running light (the red lead from the ignition sw) all okay when brake light is powered by both the front and rear brakes. So I am thinking bad ignition sw like I have read in the threads; jumped the running light from a switched power lead to isolate it from the ignition sw circuit to be sure, and the readings are still bad. I pulled apart the taillight housing figuring that I found the culprit, but can't find any problems in the wiring. I even used new wires and bulbs to be sure. I also noticed that if I install the headlight fuse, while leaving the taillight fuse out, I also get the bad readings on the switched power lead on the RR. Finally reinstalling the VOM and the horn, which are both getting switched power to their relays from the taillight circuit, as long as the running light is disconnected, the VDC stays well below .2 as the guide says it should.

I am figuring that I must be doing something wrong here, or making a series of mistakes based on bad assumptions. I hope this is the case, and there is an easy fix that I am overlooking. I thought that the problem must be in the headlight or taillight circuit, but nothing is panning out as I narrow down the possibilities. I am very frustrated, and would sincerely appreciate guidance from you folks. I have many, many hours into this, and I seem to have reached the limit of my very narrow abilities! I feel like I am wandering in the dark at this point.

I should also mention that I bypassed the bad headlight relay in the junction box by moving the blue wire to the open position in the connector, and I bypassed the RLU by jumplig the Blue and Blue/Yellow wires going into the connector after removing the RLU itself. I also installed 15A fuses on the stator leads. No other electrical system mods. Again, any/all help is greatly appreciated!! Thanks.

Chris
Wayne, NJ
1989 VN750-A5
VROC #27781
-Replaced/Fused Stator & Replaced/Relocated R/R (15K mi.)
-MF Battery
-De-Goated/Re-goated
-Coastered
-Splines Lubed
-Stebel Nautilus Horn
-AutoMeter 2" VOM
-Silverstar Headlight
-Refinished Gauge Rings and Mirrors(Flat Black)
-Refinished Swingarm/Lubed Pivots
-K&S Turn Signals Clear Cover/Amber Bulb
-Kenda Kruz 110/90-19 front 170/80-15 rear
-Clear Alternatives LED tail light
-Plexifairing III
-Willie & Max Saddlebags and SissyBar Bag
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post #2 of 4 (permalink) Old 06-09-2008, 12:32 PM
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Wow, I'm impressed. You have a whole lot more patience than I do. And I like how you're working to find the problem area. Anyway, I noticed that the license light is attached to the running light. How's that look? Since the problem started after you got on the road, I'd think there's a corroded connection somewhere that has vibrated loose. One of those nasty faults that you can't see. It sounds like the taillight assembly. There are two lights in there(three if you count the license light). Can you pull one at a time and see if that makes a difference? Can you rig up something to hold and power the taillights and brake lights without using the taillight assembly in order to get the old bulb sockets out of the equation?

'04 750A- and loving it!
VROC 13864
Using a Purlator One PL14610
"Sixth gear? I don't need no stinkin sixth gear!"
If someone throws you under the bus-remember to tuck and roll
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post #3 of 4 (permalink) Old 06-09-2008, 02:09 PM Thread Starter
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The license light was ok. I powered that separate from the tail light and had no problem. I will try to eliminate the bulb sockets tonight. Thanks for the input. I'll post back the results.

Chris
Wayne, NJ
1989 VN750-A5
VROC #27781
-Replaced/Fused Stator & Replaced/Relocated R/R (15K mi.)
-MF Battery
-De-Goated/Re-goated
-Coastered
-Splines Lubed
-Stebel Nautilus Horn
-AutoMeter 2" VOM
-Silverstar Headlight
-Refinished Gauge Rings and Mirrors(Flat Black)
-Refinished Swingarm/Lubed Pivots
-K&S Turn Signals Clear Cover/Amber Bulb
-Kenda Kruz 110/90-19 front 170/80-15 rear
-Clear Alternatives LED tail light
-Plexifairing III
-Willie & Max Saddlebags and SissyBar Bag
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post #4 of 4 (permalink) Old 06-09-2008, 07:49 PM
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Sounds like you have a wire that is chafed and is partially shorting which causes a high drain on the switched power lead thus giving you high readings. Since the bike started to run poorly once warmed up, the wire may be near a heat source that causes the short when warm but covers it when cold.
We once had a tailight assembly on an F-14 that would blow the cockpit breakers when turned on. We couldn't find the problem internally even though we knew it was in there somewhere. We ended up simply replacing the assembly and let AIMD worry about the short. This may also be the easiest solution for you as well.

Jim W
93 VN 750 "Ursula"
Moved R/R 08Sep06
R/R rewire 17Feb07
New R/R, Installed 14Jun08
New Stator installed 10 Jun08
Maintenance Free Battery 12Jan08
21480 Miles
VROC #8542
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