I have an Active Plus Autocom – it’s the same one I installed in my ’02 VFR a few years ago. I’m trying to install it in my current ’03 VFR. Since the previous owner had torn the wires loose from the license plate light and I needed to fix it, I figured that would be a good place to get switched power. And it is - it runs the radar detector just fine, but it won’t run the Autocom. :ohmy:
The Autocom was solidly connected to the license plate light wiring, but didn’t work. The voltage is low – 10.8V when the key is switched on, but goes up to 11.9 when the bike is running. The Autocom works fine if I connect directly to the battery, so I know it’s good, and the battery is fully charged - it reads 12.6 when it’s just sitting.
I used the tail light for power on my ’02 VFR, so I thought about moving the connection to the taillight on this bike, but I checked first, and the tail light also only has 10.8 when the key’s on but the bike isn’t running. I never checked the voltage on the ’02 to see if it was lower on the taillight. I saw a few posts here where people said the connected their Autocom to the taillight, so I can try that, but does anyone have any other place they pulled switched power from near the rear of the bike? :smile:
Has anyone ever measured the voltage at the tail light? I'm curious if 10.8 with just the key on with a fully charged battery is typical -
The tail light should in theory have 12vdc but due to load on system this can drop & really has no major effect on the lights except they will be a little less bright. Depending on load this if fairly normal & you have also added detector load. The autocom might be more fussy operating & needs the higher volts to operate as most devices will allow a far power drop to occur & keep working. I would simply use your tail light as a switching for an aux relay & draw power direct from battery to power all the extras you have which is the set up on my 04.
Has anyone ever measured the voltage at the tail light? I'm curious if 10.8 with just the key on with a fully charged battery is typical -
10.8 is low, but it is quite a long run from the fuse box to the back of the bike. There may be something high resistance in the circuit, but you need to compare this voltage to the battery voltage at the same time. If your battery voltage is also 10.8, then you know what the issue is. If the battery voltage is a healthy 12.6 volts or so, then you have resistance (causing voltage drops) somewhere between the battery positive terminal and the light socket.
Note that voltage drops can be caused by resistance on the positive wire or the negative wire, or both. Some good tests are to check the voltage across the two pins at the connector, then move the black probe on your multimeter directly to battery negative to see if the voltage changes. This can help you determine where the resistance is, and go looking deeper from there.
Likely places where there is resistance are:
The running light circuit fuse (front right of bike, next to ECU)
As suggested, using a relay switched by the license plate light and powered by the battery should fix your Autocom problem. I agree the tail light voltage is a bit low. Mine ran about a volt lower than battery. This may or may not become a problem. Most likely resistance in a connector or switch caused by dirt or loose connection. If it gets worse it could cause over heated wiring. Keldek is right about how to investigate it.
Has the wiring recall been done on this bike? That could help voltage level.
Some common things to check for electrical health:
What is battery voltage engine idling and at 5k rpm?
Check 30 amp fuse next to battery for overheating.
Check plug between alternator and rectifier for overheating.
Thank you all for your great suggestions. :smile: The relay was the smart way to go, but I also appreciate the list of things to check that might cause the voltage drop I see.
The wiring recall was done, and it looks as if it might have been recent. I've only had this VFR for 2 months - I had my '02 for three yearsand it hadd all the problems that the original harness could cause. The bike shows signs of having lived outdoors, maybe under a carport near the beach. It has some corrosion, but isn't sun damaged. It makes sense to check everything listed, even though the harness is pretty new. Who knows if whoever installed the harness plugged in all the connectors tight?
I did find out my main problem - too many German vehicles in the family. A couple of VW cars, and his & hers BMW K1300Ss. I jumped to the conclusion that brown means ground in Japan too, but it doesn't. :blush: I had the polarity reversed when I first connected power to the terminal block where I'd already connected the radar detector and Autocom. The radar detector doesn't care how it's plugged in and worked fine hooked up backwards. The Autocom does care, but fortunately was protected from harm by design. Lucky me on both counts, I could've fried two expensive electronic devices. :ohmy: When the relay didn't work, I finally looked at a manual on line, and realized I'd hooked up ground on both sides of the coil because I used a direct ground from the battery and the wire I thought was positive from the license plate light. Duh
So, Autocom and radar detector are both working. Harness is new, and the 30A fuse looks perfect. Next weekend I'll check the other things listed, and the VFR will be ready to share commuting duties with the K bike.