jstehman Posted September 30, 2018 Share Posted September 30, 2018 So I noticed after I rewired the 30 amp fuse and I installed a fresh battery that the volts change at idle. One minute the battery reads 13.7x or so, then it slowly declines to 12.4ish then back up to 13-14 volts for a bit. Is this normal charging behavior? Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
Member Contributer thtanner Posted September 30, 2018 Member Contributer Share Posted September 30, 2018 I would say that is abnormal behavior. Link to comment Share on other sites More sharing options...
jstehman Posted September 30, 2018 Author Share Posted September 30, 2018 Great. So am I looking at the r/r or the stator? I forgot to add the previous owner has added some xenon headlights. Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
Member Contributer thtanner Posted September 30, 2018 Member Contributer Share Posted September 30, 2018 I'd run through a full work-up. Stator Testing - Bike off - Disconnect the 3 stator wires from the R/R - Start the bike (it will be running on battery power only, so dont do this for a super extended period of time) - Test AC voltage between the legs. A to B, A to C, B to C. You should see 20-30vac @ idle and 55-60VAC+ at 5k RPM - Turn bike off - Set MM to test continuity, test continuity to ground on all 3 legs. It should be infinite. - Reconnect 3 wire connector - Start bike, let it get hot to the point the fan has turned on at least once. - Turn bike off - Repeat test steps again. The results should match your previous ones. If the voltage varies on a leg, is low, or does not raise with RPM, stator is bad. If you have any continuity to ground, stator is bad. Rectifiers can be bench tested. If all tests are clean across the board make sure wiring and all grounds are clean and secure. Link to comment Share on other sites More sharing options...
jstehman Posted September 30, 2018 Author Share Posted September 30, 2018 Looks like I've got something to do Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
jstehman Posted October 1, 2018 Author Share Posted October 1, 2018 Cold motor: Stator phases all read ~20vac at idle and increase up to ~60vac as revs rise. Stator did not get any readings to indicate it was shorted to ground. Warm engine ~215d: Stator phases all read ~20vac at idle and increase to ~60vac as revs rise. R/R passed diode test like the video showed. Got readings on all pins. I cleaned and greased all connectors on the RH side of the bike while I was there. Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
Auspanglish Posted October 1, 2018 Share Posted October 1, 2018 The tests available to the average Joe with a multimeter are not 100% conclusive. The r/r may need renewal. Check your wiring loom, especially the usual suspect connectors. This is one of them... https://r.tapatalk.com/shareLink?url=https://www.vfrdiscussion.com/index.php?/forums/topic/62525-faulty-ground-connector/&share_tid=62525&share_fid=35196&share_type=t Then there's the big blue and grey ones near LHS radiator and the ones near the battery. Link to comment Share on other sites More sharing options...
jstehman Posted October 1, 2018 Author Share Posted October 1, 2018 So the R/R can still be failing even if it passes the testing with the multimeter?Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
Member Contributer thtanner Posted October 1, 2018 Member Contributer Share Posted October 1, 2018 If it's intermittent, it could definitely be the R/R. I'd re-check the charging voltage since you've tidied connectors, etc. For peace of mind, there's always that SH847 I was speaking about 😄 Link to comment Share on other sites More sharing options...
jstehman Posted October 1, 2018 Author Share Posted October 1, 2018 Ok I'll have to pull the LH fairing in the next few days. The measurements were made after the connectors were cleaned. Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
squirrelman Posted October 2, 2018 Share Posted October 2, 2018 You removed the plug atop the starter relay and inspected/cleaned contacts ? Link to comment Share on other sites More sharing options...
Auspanglish Posted October 2, 2018 Share Posted October 2, 2018 Yes So the R/R can still be failing even if it passes the testing with the multimeter?Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
Auspanglish Posted October 2, 2018 Share Posted October 2, 2018 Are you testing the stator with the connector unplugged? I assume so. This is the correct form. If so, Stator seems good. It is always advisable to start with the most simple : have your battery load tested. Experienced suspicion say it's the r/r but this is just that, an inkling... scientific method of ruling out is the only fail safe way. Unfortunately yes, the r/r diode test isn't 100% conclusive. Link to comment Share on other sites More sharing options...
jstehman Posted October 2, 2018 Author Share Posted October 2, 2018 Yes the stator test was done with the harness unplugged.Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
jstehman Posted October 2, 2018 Author Share Posted October 2, 2018 No I haven't cleaned the starter relay. YetSent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
Member Contributer MarkDetroit Posted October 4, 2018 Member Contributer Share Posted October 4, 2018 On 9/30/2018 at 6:49 PM, jstehman said: So I noticed after I rewired the 30 amp fuse and I installed a fresh battery that the volts change at idle. One minute the battery reads 13.7x or so, then it slowly declines to 12.4ish then back up to 13-14 volts for a bit. Is this normal charging behavior? Voltage output at idle is never very impressive. Is this like 1300 RPM? What's it like above idle - like 3000 and above? How many miles on your bike? Link to comment Share on other sites More sharing options...
Member Contributer thtanner Posted October 4, 2018 Member Contributer Share Posted October 4, 2018 17 minutes ago, MarkDetroit said: Voltage output at idle is never very impressive. Is this like 1300 RPM? What's it like above idle - like 3000 and above? How many miles on your bike? He posted a full charging work up a few posts back. While charging at idle is not the best, it shouldn't be doing that big of a dip intermittently. Link to comment Share on other sites More sharing options...
Tightwad Posted October 10, 2018 Share Posted October 10, 2018 Charging at idle may not occur at all, depending on where your "idle" is. At 1100 RPM voltage from the stator can be 18 VAC...when rectified it may resolve as <13V easily, especially with lights on and possibly the cooling fan etc. If by 1500 RPM you aren't over 13V then you need to look deeper. I see nothing wrong with your results, what voltage are you getting at 5K rpm? Link to comment Share on other sites More sharing options...
jstehman Posted October 10, 2018 Author Share Posted October 10, 2018 Charging at idle may not occur at all, depending on where your "idle" is. At 1100 RPM voltage from the stator can be 18 VAC...when rectified it may resolve as Voltage is approximately 13.7v above idle.I did not rev the motor to 5000. Only about 3500. The voltage increased to 13.7 as soon as the revs rise past idle.The voltage drops to about 12.4, 12.5 with the fan running at idle. After the fan shuts off, the voltage starts to climb back.Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
Tightwad Posted October 10, 2018 Share Posted October 10, 2018 13.7V is on the low side, but acceptable. If your parts are all OEM it may be "normal". Aftermarket R/R is set to 14.6V (Ricks is) and the Shingeden ones I believe are 14.4/14.5 or so. I'm not a fan of throwing parts at a bike or a car...I'd make a horrible paid mechanic... If 13.7V makes you nervous, you can change out the Stator and R/R and bolster the wiring, you will get 14.4V + Link to comment Share on other sites More sharing options...
jstehman Posted October 10, 2018 Author Share Posted October 10, 2018 Parts are OEM from what I can tell. I'm not having any charging issues at the moment. Battery is a few weeks old, bike has been sitting for about a week because of rain and low temps and the battery reads 12.8v Previous owner had a battery that left standing after charging was 12.4v so I was double checking the charging system if I'm going to put in a new battery. Sent from my SM-N950U using Tapatalk Link to comment Share on other sites More sharing options...
Member Contributer Hingley Posted March 23, 2019 Member Contributer Share Posted March 23, 2019 Well guys I am into my 1990 VFR750 wiring/charging system ( dump as a post with wiring/voltage ) I was having a hard time getting the bike to fire up after sitting for a few days ( not sure if the fuel pump is 100% or the float valves in the carbs are leaking by ) anyway when I was trying to get her to pick up the fuel the starter would only engage for a cycle of two and then disengage After looking around I found the starter relay wires were cooked so I fixed that and at the same time checked and cleaned all the grounds I could find So I finally got her to fire up ( starter would still only engage for a cycle of two and then disengage ) after all this I started to check voltage readings Battery sitting 13.6 volts Battery after short engine crank drops to 12.6 volts Bike running at 1200rpm 14.6 volts Bike running at 5000rpm 14.1 volts Do these numbers sound like they are in the ball park? At 5000rpm I would have thought the voltage would be steady or rise a little, not drop I should add the bike has a cheap aftermarket ( Tour Max ) voltage regulator, and the bike has roughly 10,000 miles on it Link to comment Share on other sites More sharing options...
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