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98 900ss 40amp fuse keeps blowing!

7K views 12 replies 7 participants last post by  Snoopy 
#1 ·
So after many many hours of forum surfing mixed with over 40 hours of looking for pinches, exposures ect. I'm at a breaking point. My biggest problem being I cant get to harbor freight to get a meter I can afford.
I've found posts saying people installed their battery backwards...not the case. Another saying he was stupid and connected the positive lead on his battery first then when doing the negative he got a spark and it blew the fuse. I'm having the same problem...but I thought you always connect the pos. lead first then the neg. or did I not get that memo? It sparks even when the bike is off...then pop goes the fuse.
All grounds are clean and clear, no exposures, black residue from poping or overheating from anything anywhere on the bike. Any ideas?
 
#3 ·
Set it to Ohms and disconnect the battery leads. When you have both leads free, touch the meter leads to them r-r, b-b, see if there is any continuity. Should be infinity with the key off, if you have continuity fuse will blow. You'll need a good fuse in there to check it.
After that it becomes a case of finding out what the original problem was, or what you created trying to fix the original problem.
Use the volt meter to check the polarity on the battery? Never know.
 
#4 ·
40 amps is a BIIIIGGGG fuse, so you've got a serious short circuit somewhere. The fuse is doing its job.

Negative terminal hooked up last (and disconnected first, when removing battery or disconnecting it) is correct on a negative ground bike, so don't worry about that.

Your comment about sparking when ignition is off makes me think I'd have a good luck at that switch while you're at it. Perhaps its shorting internally or some connections are touching, etc.

Lots of tutorials on multimeter use online. Once you know a bit about how to use it, you'll love it - absolutely invaluable tool.

Best of luck, and please report back as you make progress!
 
#5 ·
Feeling my way around this meter now. My battery read 13.6 as it sits, and 12.6 when starting the bike. (with no 40amp fuse ie r/r) after disconnecting the battery, then setting it to Ohms 20m it automatically goes to -1 . -
I tested the leads as well as all of the fuses, and all gave a 0.00 reading. Is that normal? And why does the meter reset at 1 . ?
 
#7 ·
If you look at the attached circuit diagram you will see that the rectifier is the only thing is connected to the battery via the main fuse when the ignition is off.

The wiring is battery positive to fuse (#25) through connector (#3) then via the red cable to the rectifier.

Therefore the problem is in this part of the circuit. I suspect that the rectifier is stuffed and allowing a short circuit to battery negative/frame.

It is simple to test this with your new meter. On the meter dial there are a series of positions that all start with 2. I.e 200, 2k, 20k, 200k, 2M, 20M and 2000M. This is from 6 o'clock to 9 o'clock. Set the meter to 200.

I can't read the cable colours on the attached diagram, but you want to test With the fuse out, test the resistance between the 2 colour cable side and battery minus. If resistance drops to zero, then the short is in that circuit. Then disconnect connector (#3) with the meter still in place. If the resistance is zero, then there is a short is between the fuse and connector #3.

That 1 . you mentioned means infinite resistance, which is what you see when the test leads are not connected to anything. Mine shows .OL, so it is just different ways manufacturers set up the reading.

If it is 1 . then fuse to connector #3 is OK, so test from the rectifier side of connector #3 to battery minus. If zero then the problem is in that part of the circuit.

I really feel your rectifier unit is stuffed. I don't have info to hand at the moment, but think you should search on how to test that unit.

Richard
 

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#8 ·
If you look at the attached circuit diagram you will see that the rectifier is the only thing is connected to the battery via the main fuse when the ignition is off.

The wiring is battery positive to fuse (#25) through connector (#3) then via the red cable to the rectifier.

Therefore the problem is in this part of the circuit. I suspect that the rectifier is stuffed and allowing a short circuit to battery negative/frame.
I agree.

Unplug the regulator, and try again.

If the fuse doesn't blow, your regulator is fried.

If it does blow, you have a short somewhere.

Tom
 
#9 ·
The above two posts are 100% correct. The rectifier diodes are short circuited and this is why the fuse blows when you connect the battery. So indeed the fuse is doing it's job of protecting the bike in the case of a failure in the RR.

Sux, that the RR is up the duff, but at least you've found your problem.

Cheers.
 
#10 ·
Hey guys, I cant thank you all enough for all the input. This being my first ground up build/first engine I've ever touched, as well as being 100 miles from any Ducati dealers this sight and your help is priceless. And yes I found the problem! Finally! Anyone know a good sight I can order my new rectifier from?
 
#11 ·
There seems to be a few options and of course opinions. Try these threads to get some informed opinions.

http://www.ducati.ms/forums/57-supe...et-regulator-rectifier-debate-answered-2.html

http://www.ducati.ms/forums/57-supersport/58290-900ss-regulator-rectifier-2.html#post551441

Electrosport 510M seems to get good reviews.

There also appears to be one from Electrex.

Rick's motorsport electrics Rick's Motorsport Electrics - Product Detail

va duc posted this link in another thread Ducati 900 904 906 907 Regulator Rectifier -

Greenmonster posted this "This Shindengen FH0012AA mod whas made recently on a 916 SPS w same good result as OP."
 
#13 ·
Hey, thanks for all the help guys. Like I said b4 this is my first ground up build, and actually a gift from the original owner. Just completed the build (with no money or tools) and road it from my hometown Louisville Kentucky, to apparently my new home Orlando Florida. Now I'm somehow enrolled at MMI...anyway got the R/R in, plugged it up, bolted it on, fires first time every time. Thanks for the help! Your time spent wasnt a waste! See you on the twisty's
 
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