Keeps popping main fuse....

[mrpink]

Riding home from a buddies last night, bike running very well. All of the sudden, black. Nothing. Coasted off to the side of the road and walked it to a safe place to work on it. Found the main 20A fuse blown. Got a lift to a gas station to get a replacement. Popped it in and it started right up, only now, the headlight was not working. Got it about another couple of miles up the road and it blew again, this time I was near a school with a large, well lit parking lot so I left it there for the night. Trailered it home this afternoon.

I have done zero inspection on it, just looking for a good place to start. I have little to no experience with electrical issues so use small words and talk slowly....


thanks



matt

 

[xjwmx]

The most likely thing is worn off insulation causing a short to ground. Maybe up in the headlight. Although it could be a bad component. First thing I would probably do is disconnect the battery and put a meter on the cable and the other side on the frame and move wires around until the meter flips a low resistance to ya. It's handy if the meter has a continuity test that beeps at you when it sees low resistance. You'll know the short is somewhere in that vicinity and then you can track it all the way down.

 

[TeeCat]

The most likely thing is worn off insulation causing a short to ground. Maybe up in the headlight. Although it could be a bad component. First thing I would probably do is disconnect the battery and put a meter on the cable and the other side on the frame and move wires around until the meter flips a low resistance to ya. It's handy if the meter has a continuity test that beeps at you when it sees low resistance. You'll know the short is somewhere in that vicinity and then you can track it all the way down.

Ditto. This happened to me and I traced it to missing grommets in the headlight bucket where the harness passes through. I installed grommets and have never been able to reproduce the issue since. Hopefully yours will be something similarly evident and easy to rectify.

TC

 

[mrpink]

So the headlamp and headlamp wiring should be my first suspect (only saying this because the head light did not come back on when I replaced the main fuse)





p!nK

 

[EvenmoreXS]

Was there ever a solution for this problem???? Im having this exact problem now. Ive got the bike running but the headlight doesnt come on. Scared to ride to far and be stranded again. I looked all throught he headlight bowl, its a mess, but no real smoking guns. Any help is appreciated.

 

[retiredgentleman]

Was there ever a solution for this problem???? Im having this exact problem now. Ive got the bike running but the headlight doesnt come on. Scared to ride to far and be stranded again. I looked all throught he headlight bowl, its a mess, but no real smoking guns. Any help is appreciated.

Always start trobleshooting with the simple items first. Is the headlight fuse good? Is the headlight bulb good?

The headlight is turned on via the Safety Relay. In order for the Safety Relay to turn on, it must have a strong voltage signal from the alternator. Therefore, you now want to measure the battery voltage (indicates alternator output) with engine off, engine at 1200 rpm , and engine at 3000 rpm. You should read 12.5 volts, 13.5 volts, and 14.1 to 14.5 volts if all is normal.

If your bike still has those old OEM (glass type) fuse holders...............get rid of them and use automotive, blade type, fuse holders.

 

[5twins]

There's also a safety item called the RLU (Reserve Lighting Unit). It's supposed to turn your high beam on if the low beam goes out. They go bad and can cause all sorts of weird headlight and electrical problems. Best thing to do is just eliminate the thing. It's as simple as removing it and installing a jumper wire between 2 of the wires in the remaining plug. Instructions are here .....

http://www.excess650.co.uk/tips & tricks.htm

 

[halliday77]

I had a main-fuse problem recently and I'm sorry to say it took me two full weekends of diagnostics to figure out. I too didn't have any experience with electrical gear, but the forum members were priceless in their advice.

It's about isolation and testing, and SHEDLOADS of patience.

- Check all your fuses are good first. Then go buy some replacements anyway.

- Unless you want to burn through a million replacement fuses during testing, buy a mutimeter and learn how to use it to test for 'continuity'.

- Try and re-create the blown fuse. If it does it as soon as you switch the key, then it's either a permanent short to ground or a bad component. If it doesn't blow immediately, do stuff until it does: blow your horn, turn the signals, hit the brakes, physically turn the bars side to side, shit, rattle the bike side to side! One of those things should blow your fuse. Work out which.

- If the fuse is blown by using a component, remove it, and either test that component with your multimeter, or just try to blow the fuse again with the component out. If the fuse lives - your component has problems - fix or replace. If not - onto the next component.

Mine turned out to be my automatic signal canceler. I don't even fucking NEED IT!! What's worse - is it's the last bloody thing you'd think of, and it's tucked away under the tank - thus two whole weekends of testing.

Good luck mate.
Let us know how you go.
The forum members love problem solving and are plenty helpful and patient.
Worst case scenario - you'll learn some new stuff!

 

[EvenmoreXS]

First off, Thanks everyone for the help. Heres is where i am now and my symptoms. On sunday I traced everything i could with the lighting system and no shorts to be found other than a intermitent short in the tail light which seems to not be the problem. I can make the tail light short and blink on and off by tapping the wires coming out of the tail light, bad bulb socket, but it doesnt affect the bike running or the fuse operation. Cant make it blow the fuse. Cant reproduce the issue by shaking the wiring harness anywhere. I have double and tripple checked the ugliness that is the inside of my headlight bowl and no problems.

I will be replacing the tail light soon. So thats that.

But here is what I did:

Removed the reserve lighting device. Not necessary for me.

Removed the starter/lighting relay. Starter button not working so I cant even use the starter now anyway. I prefer the lights come on with the switch now anyway until I wire an on/off switch on the bars.

Wired the headlight to come on with the switch, like the tail light,... Turned on switch and BOOM, there was light. Bike crunk right up. Very happy camper......

Rode the bike for 20 mins around my neighborhood with no issues. YEAAAAAA.

Rode 9.5 miles to work in traffic with no issues, YEAAAAAA.

Left work and rode one block and blew the fuse. Replace fuse. Turn switch and blow fuse. Replace fuse. Turn switch and everything is fine. Crank bike and ride 5 miles and blow fuse. Replace fuse. Bike cranks fine and I finish my ride home.

To me, the odd part is this. .....I blow a fuse. Replace the fuse, turn the switch and blow the next fuse. That should happen everytime if I have a short. Why then, when I put in the next fuse and do absolutely nothing different, does it not blow the fuse and let me drive off. If it was a short, it should blow the fuse everytime.

Regulator Rectifier problem??????? Any good ways of testing this device??????

Slap test is good, still going to put on new brushes though soon.

Gonna do some more volt meter testing tonight.


Thanks everyone.

 

[XSLeo]

In the stock harness, the tail light runs straight off the main fuse. It often gets a short on the hot wire to ground, This can be an intermittent short. Intetmittent electrical problems are the worst.
The rectifier is a bucnh of diodes hooked up to convert AC from the alternator to DC to run the bike. If one or two of the diodes are bad you can get a short from battery hot to ground, but this will be there key on or off.
To test the reg/rec your repair manual tells how.
On your safety relay that controlls the starter and headlights. To remove it and still have the starter work jumper the two red/white wires together. This sends power to the starter relay so the starter will work.
Also if you put your bikes info in your signature we could do a better job of helping. Things did change over the years.
Put your bikes year,model and any mods done.
Leo

 

[5twins]

These are old bikes. When you get one, you really need to go through the wiring and make it right. Start at the tail light and work your way up into the headlight. Clean, inspect, repair the wires and connections. I found 3 or 4 rubbed bare wires on mine, problems just waiting to happen. I've had no major electrical problems since I put the bike in service a bit over 6 years ago. I have had a couple minor electrical glitches but nothing that stopped the bike or blew a fuse. My self canceling unit does sometimes, doesn't at other times. My brake light indicator on the dash stopped working for a while but is now back. Same with my TS indicator on the dash. Lately it's been indicating sometimes, sometimes not. The signals flash fine, just the indicator is on the fritz. Like I said, none of these things are killing the bike, so I haven't investigated them further.

 

[EvenmoreXS]

Thanks for the advice. I figured out how to put my info in my signature. That should help in the future.

I will check for any additional shorts between my tail light, headlight, and battery tonight. One additional note about my symptoms BEFORE removing the reserve lighting module and the starter/lighting relay..........

When my fuse did blow, and I replaced it, the bike would crank but the headlight would not come on. Thats why I originaly took the relay out, not that i particularly wanted it anyway. Thought the relay was bad. After removing and rewiring, things seemed to work fine, and I was happy, but then blew a fuse again. Just riding, no particular BEHAVIOR that I can account for. I've read that this could be a issue with my charging system. Maybe I need new brushes. That would acct for the headlight issue, but not necessarily the fuse being blown. Brushes are cheap, doing that anyway. Could bad brushes cause me to have this recuring problem?

P.S. I love my bike. Not frustrated at all with it. Im going to know everything there is to know about it. This is how I will get there.

I appreciate everyones help. This is a great forum.

Thanks.



1981 XS650

 

[XSLeo]

The safety relay was originally to protect the gear of the starter to engine system. When you first turn the bike on the safety relay is set to let the starter work. When the engine starts, the alternastor starts to produce electricity.
Some of this electricity is sent to the safety relay. When the engine starts the voltage of the electricity increases rapidly. When it reaches about 4.5 volt the safety relay trips to cut the power to the starter, this protects the gears from being damaged by over run from the engine.
On the later 78 or 79 they incorporated the headlight turn on into the safety relay. This was to keep the headlight off so more power went to the starter and ignition. Once the engine was running the headlight comes on.
No matter how fast your thumb is it is not as fast as the safety relay is at protecting the gears.
On the headlight turning on, if the alternator is not putting out enough voltage it can't trip the relay to turn the headlight on. So yes, a no charge situation can keep the headlight from working.
Check the brushes first. If to short, about 3/8 inch, you need new ones.
Once they are in check for charge. At idle around 12.5 to 13 volts or so, at above 2500 should be around 14.5 and never go over 14.5 at any rpms.
Be sure the battery is fully charged and use the kick starter when testing. This saves on battery power.
If no charge then you need to go through Curly's charging guide. The folks on here went through it and added a bunch of pics to help with the process. It's on here somewhere.
Leo

 

[EvenmoreXS]

I think I got all that. BUT>>.......Would that blow my fuse?????? That being worn brushes....

I am planning on replacing the brushes regardless of the answer.

Not currently using the starter at all. Hell, it isnt that hard to kick. Even cold, ususally no more than 2-3 kicks. Great bike, just gotta find my gremlin. Maybe its on the wing.??

Did my signature twice now and it still isnt showing up in my post. I'll get there.

 

[EvenmoreXS]

Signature.......

Check !!!

 

[EvenmoreXS]

So. I traced the wire that keeps blowing the fuse. I have a theory. I hate probing, but i had to. Didnt want to open the harness, but i had to. Wire goes directly from the battery to the ignition switch. It runs under the gas tank and loops back to the switch. Weird, but anyway. Couldnt find a short. My bike has metal battery covers with numbers painted on them, my brothers racing number, and I believe that it must be possible that the cover was contacting a terminal and shorting to ground and blowing the fuse. Just a theory. I CANT REPLICATE THE FAILURE. I HAVE TRIED EVERYTHING.. But I dont want to test it by touching the wrong thing and frying everything. SEE photos. Two show you the cover. The other shows the terminal i believe made contact randomly to blow the fuse. Please tell me in your opinions if my metal, grounded, battery cover made contact with the terminal in question ( the one in the red circle with the red arrow ) Would it blow the fuse???? The yellow arrow points to the wire in question that is directly connected to the fuse im blowing. Appears to be nothing else on it.

What ive done. Wraped the terminal in several layers of electrical tape and zip tied the tape on to the terminal, imagine an electrical tape cap......, temporary fix, also, there is as you will see in the photos, a layer of thermal .....stuff....the silver stuff on the inside of the cover in the photo, put there by the PO to prevent contact. Obvious wear there. I have an additional layer there now also, folded, double thick. Rode it for 10 mins or so with no issues.

Let me know what you think.

Gonna ride it to work tomorrow. How do you know if its fixed if you dont ride it?????

Thanks

 

[kenintn]

To me, the odd part is this. .....I blow a fuse. Replace the fuse, turn the switch and blow the next fuse. That should happen everytime if I have a short. Why then, when I put in the next fuse and do absolutely nothing different, does it not blow the fuse and let me drive off. If it was a short, it should blow the fuse everytime.

From what you noted you most likely have what's called a threshold current failure of the main fuse. SAY WHAT???
Fuses are designed to blow at a certain current within a certain time. The time required to blow the fuse once it reaches its failure rating is inversely proportional to the current the fuse is seeing. Simply stated, the more current the fuse see past it rated value the quicker it will blow. A 20 amp fuse will actually not blow as soon as the current reaches 20 amps. It might last 1 or 2 minutes depending on things like the ambient temp and such.. But kick the current up to say 30 amps and it will blow fairly quick.. ( To those that know fuses don't misconstrue this info with a time delay fuse since they are rated to fail at a much higher percent over current rate.)

Back to the threshold current statement.. Your fuse is could be seeing current hovering just below or right around its failure value. You start your bike up, take off, all seems OK. But then you apply the brakes, or turn on the turn signals, this throws 3-4 amps more on the fuse and it finally melts. Or maybe just the headlight coming on puts it on the edge. (I will note that from your comments on the randomness of it blowing there could be other issues but I'd at least check this)

So how can I tell if this is happening? Simple, connect an amp meter in series with your main fuse. With the bike running the current should be below 8-9 amps or so depending on if your headlight is on/off, and such. If you're seeing upwards of 17-20 amps you've got a problem. And if you do, where is it at???

There are only 2-3 things on the 650 that can draw this kind of current and not go up in smoke. The rotor is one and it has been my experience it's the #1 culprit behind problems such as this. If it's shorted it can draw upwards of 20 amps itself. And with due respect to the slap test, a shorted rotor will still create a magnetic field even while drawing major current. Once again, it might not be the rotor but its a simple test to rule it out by measuring its current. No need to run the bike, just connect your amp meter in series with the hot brush lead and turn on the key, read the amps. It should be right around 2.25 amps. More than 3 amps and you've got rotor problems, time for a replacement

If your rotor checks good and your current looks normal look at the grommets going through the headlight can and see it they've cut through and if any wires have rubbed through and are touching the can. Note there are some more checks you can do if the above doesn't uncover your problem.

Good luck and lets us know what you find. Inquiring minds want to know.

Ken


http://tinyurl.com/45ywb6a

 

[kenintn]

My bike has metal battery covers with numbers painted on them, my brothers racing number, and I believe that it must be possible that the cover was contacting a terminal and shorting to ground and blowing the fuse. Just a theory.

FWIW the terminal you have circled is the starter solenoid terminal that feeds power to the starter motor and it is never hot unless you are trying to electric start the bike.
If this lug is your concern its not likely this is the problem.

Ken

http://tinyurl.com/45ywb6a

 

[nj1639]

Take your voltmeter and check that starter wire (circled in red) to see if it's got voltage with the key off and then on. There should be a rubber boot on there just like the battery lead coming down to the solenoid.....

 

[EvenmoreXS]

Thanks. I will check the voltage at the starter solenoid and the positive brush on the rotor tonight. I will try to get a rubber boot for that terminal too. I did ride to work this morning, risky i guess, but it rode great. No worries. I dont want to replace a rotor, but I will if i have to.

Hey Ken,

Could badly worn brushes cause this???

I'll let you know what happens tonight.