Fuses blowing on 1980 GS550

[Anonymous]

I own a 1980 GS550 (106K mi.) that?s still running great however; I have some ongoing ?quirks? with the electrical system (no surprise). I have replaced the stator and regulator/rectifier once after a spectacular all-at-once every bulb and fuse blow out but until recently reading your Stator Papers I wasn?t aware of the $250 upgrade that is available from Electrex so these were replaced with stock Suzuki parts. The main problem is that every 1500 to 2500 miles either the 10amp headlight fuse or the 15amp main fuse will blow. I?ve never been able to connect this with any other contributing factors. Electrical checks of the stator (73 volts each phase) and regulator seem to be normal other than the fact that as RPM?s increase, voltage at the battery decreased from 14.2V at 1600 RPM to 12.8V at 4000 RPM. This is with the lights on. The battery holds a charge well and doesn?t need charging during the season. Here?s the questions; when I check the fuses I see that some of them are 32V and some are 250V what is the difference and what?s correct? Any ideas on what?s causing them to go? Also, if I ever get this problem figured out, I would like to run a 55w/100w low/high beam halogen headlight rather than the current 55w/60w (I converted from the original sealed beam years ago). Will the current stator/regulator and wiring systems handle this?

Update: Sorry for the incorrect info. Voltage at the battery is as following: 2000RPM = 13.7v, 3000RPM = 13.3v, 4000RPM = 13.25v, 5000RPM = 13.15v. Reading voltage at the head light fuse never exceedes 12.3v.

[Anonymous]

Well, there must be something that creates a shortcircuit somewhere.
My first guess would be damaged insulation somewhere in the wiring harness.
Most likely would be worn insulation near the steering head, where the wiring comes from under the fuel tank and goes to the headlight and handlebars.

[nert]

are there any extra tail lights, marker lights, etc. like a truck or saddlebags? Is the fuse burnt/popped "black" in the center, or melted slightly, or melted towards one of the ends?

[Anonymous]

Thanks for the replies. I'll be taking a closer look at wiring and connections today. After reading other forum letters I checked to see if the head light fuse was getting hot and infact it is getting hot, only on the left end of the fuse (as you look at the fuse block). I honestly don't recall how the fuse looked when it went last since it's been a few months but I will watch that now. There are no additional lights or equipment.

[nert]

if you have localized "heat" its usually caused right there at the connection and is failing due to heat, (loose fuse holder or corroded/poor connection) not because of a short. That may also explain the inconsistant failure. A short will usually give a blackened break in the element, (and/or a piece missing from the element.)

[Anonymous]

Well, I disassembled the light switch and cleaned the contacts for both the on/off and high/low switches. Both were heavily oxidized and dirty but no real corrosion. I also cleaned the clip connections on the fuse holder. Again some oxidation but no corrosion. While doing this I did notice however that there is a discrepancy between what the sticker on the fuse cover says as to the order of the circuits and required fuses and the wiring diagram in the Clymer Service Manual I have. First off, the order of the fuses (top to bottom in the fuse block) doesn?t match what the Clymer shows and the color of the wires in the Clymer manual don?t match with what I have either. Secondly, according to the Clymer, the headlight fuse is a 15 amp. The fuse cover on the bike calls for a 10 amp. Do you think this would account for the heat build up I mentioned earlier on the one end (power to the fuse side) of the headlight fuse? Perhaps a larger fuse should have accompanied the change over from the old sealed beam with a 40w/50w bulb to the halogen unit with a 55w/60w bulb? Does anyone know where I could obtain a accurate wiring diagram?

[vapourman]

if it blows again look at the fuse and check if it appears to have had a mini explosion or if it looks like a piece of the link has melted off. If there is heat in the connection it will melt the fuse. All fuses have a thermal break point and a current break point. It is easy to check amps draw, get some old blown fuses and shave the plastic back. use alligator clips to attach meter probes to exposed links on blown fuse. Set meter to high current, start bike then reduce amps range for best accuracy.

[jimcor]

Nert might have this nailed for you, Doug. Check that fuse box, mine had dirty/loose contacts and was causing a high resistance situation which was causing a LOT of excess heat. The solder in the fuses was melting rather than 'blowing' the filament.(correct term?) Clean all the contacts in the fuse box. Replace all the fuses, mine are 250V rated, they're cheap enough. Also if you're feeling energetic you mihgt check and clean all chasis ground contacts and the connectors on the wiring harness.

Headlight bulb: If you go to the hi watt bulb you will generate enough excess heat to melt the stock zooki headlight connector. NAPA auto parts sells this connector in a hi temp material. Unfortunately I no longer have the part #. Might ride your bike to the parts house and if it's a slow day get the counterman to look and see if he can match one up for you.

Hang in there Sparky! 8O The 80 550 is a bike that builds character! :? :?

[Anonymous]

JIMCOR, I see you have experience, as I do, with the melted headlight connector. It only took a short trial with a 100 watt high beam bulb to discover this. Thanks for the NAPA tip. I'll check it out. All connections are cleaned up and I'm heading out for an all day ride. I'll let you know if there are any developments. By the way, what type of headlamp are you using and what amperage fuse?

[jimcor]

Doug, I went the cheap route and just put my old 55/60 watt bulb back in. My high watt bulb is in my tool box as a spare! Standard fuse (as called for on the fuse box).

[Anonymous]

Re: Fuses blowing on 1980 GS550

Update: Sorry for the incorrect info. Voltage at the battery is as following: 2000RPM = 13.7v, 3000RPM = 13.3v, 4000RPM = 13.25v, 5000RPM = 13.15v. Reading voltage at the head light fuse never exceedes 12.3v.

I think those voltages are not good. It's supposed to be higher than that. My RR was putting out less than correct voltages and, while my battery never went dead, it wasn't good either. Perhaps on rare occasion your RR puts out very high voltage rather than kinda low. This will cause your electical accessories to draw extra current. The biggest one of these is the headlight, so I'm gonna say that I think your headlight fuse problem is related to a bad charging system. If you upgrade now you may be able to save the stator and only replace the RR before the stator goes down with it.

Of course, it's all speculation.

Michael

[Anonymous]

While checking voltages and resistance throughout the system I discovered that there was quite a bit of resistance through the ignition switch when it was in the on position. The red output from the RR goes directly to the ignition switch and comes back as orange to supply all three fused circuits (head light, ignition, turn signal). I took the switch apart and discovered that the copper contact was virtually gone. I replaced it and the resistance dropped as well as the heat at the fuses. I?m waiting to hear back from ELECTREX USA as they are testing my RR .