Literally had a meltdown today

85 xj700. 11k mi. Just finished tucking the wiring back behind the rectifier. Rolled her out of the garage after doing some detail work to her, and she wouldn't fire. Ran fine yesterday. Tried to start her for 5 mins. Figured out that I wasn't getting spark on 1 and 4. Traced it to what I believe was a loose connection at the cdi. Put two zip ties around the cdi connectors and took it for a ride. She only ran on 3 cylinders...period. This from a bike that ran great on all four the day before. Come to find that the red wire that runs from the harness to the rectifier had literally fused itself in the connector. I had to remove the connector from the harness via a pair of wire cutters and then work a thin screw driver around the connectors while in a vise to get it free with two other screw drivers prying upwards.

Once I got it apart, I couldn't believe how hot this thing must have gotten. The male end of the wire coming from the rectifier was actually turned inside the connector and looked to be charred

Now, the 60k dollar question...what would cause this? I have access to another harness, but is the rectifier still any good? My first thought is no. I'm wondering if my messing with the cdi overloaded something somewhere? This bike has given me tons of fits, and I really thought I had it good to go today after doing some pretty cool detailing to it. All thoughts are appreciated.

 

I would immediately suspect the Voltage Regulator is bad. That RED WIRE Melt is THE ... #-1 ... Classic symptom of the Electrical System being introduced to more Amps that it was designed to handle ... Frying the Regulator and having more Juice applied to the system than the wiring harness has the capability of safely handling.

There isn't a "Plug-in" tester for the Voltage Regulator. It's tested buy hooking-up Jumpers and TWO Multi-meters.

Rather than "Waste Time" running the Voltage Regulator tests (with the BOLD LETTERING CAUTIONS) as prescribed in the Factory Manual; most Techs have a known GOOD Voltage Regulator they Plug-in and use to see how the machine's Electrial System -- with emphasis on System Charging ability -- is without "Going through the motions" to declare the Burned-out Voltage Regulator BAD.

This problem has become more common lately.
These days, automotive alternators are capable of generating Amperages WELL OVER the Design Limit of these Bikes.

It wasn't to much of a risk to Jump Start an XJ-Bike when the Car only had Electric windows and an AM/FM Radio.

A "Fully Loaded" Sedan or SUV has so many power-hungry options ... that hooking-up your bike to it's Battery with the 4-wheeler's engine running is like wiring a Flashlight to Hydro-electric Plant at Niagra Falls.

 

Your bike, or any other electrical device will consume only what is required to operate the device connected. I can jump my bike from a Marathon Motorcoach, if I have to. Take the biggest, High Output alternator, Let's say it is rated at 500 amps - connect it thru the regulator to a bank of 900 CCA (Cold Cranking Amps) rated batteries. Then take a little "seed bulb" from the instrument panel and wire it with tiny 22 ga wire. What happens when you connect the bulb across the terminals?? The light glows with it's rated 4 watts. Hook up your Yamaha Starter, with proper heavy gauge wire and it cranks at it's rated draw, too. Nothing is going to explode, or burn up. Try to run that starter thru the same tiny 22 ga wire, and you will see smoke! The wire will act like a fuse, because it can's supply the current.

Corrosion and loose connectors, now That will cause similar problems! Heat being one of them. Your red wire acted as a fuse, because there was something "down stream" consuming too much current, well above it's normal rating. Your regulator failed? Perhaps. More likely corroded or loose connectors

 

so what is my next step here? Can I just resplice the wires and put a known good rectifier (regulator) on it and go from there? or should I just heave the old harness and go with the other one?? I'm really curious as to what caused this...corrision is an interesting suggestion. Now the bike only runs on 3 cylinders...and it only happened when this meltdown occured. Is there a 'connection' there?

 

I would splice in new wire and connections between your alternator and the rectifier. Then see what the alternator is putting out in terms of voltage and if you can swing it, amperage.

 

sounds to me like you had too much load on the system for it's design. Hence the fused connections.

Running on 3 cylinders is another thing.

If a hot wire burned into or thru a spark plug wire then maybe that would cause 1 cylinder to drop out, but each coil serves 2 cylinders, so I wouldn't necessarily blame the coils.

When you try grounding out a spark plug on that plugwire do you have spark?
If so then you have something else going on there.
If not, I'd start looking into a bad plug wire!?
I'd suspect a fouled plug from when the CDI had the loose wire.

Good Luck

By the way, if you hooked Hoover Dam to a flashlight you would have no problem as long as you rectify the voltage to that of the flashlight.
The load is determined by the flashlight (the load) not the power source.

By the same token you could jump your xj with a big suv and be ok but you wouldn't be able to jump that same suv with your xj because it would over load the battery and if you had your bike running they it would overload the system and burn it up. did you add any extra load to the bike?

 

no extra load was put on the bike. Nothing out of the ordinary was done to the bike. It wouldn't fire but on 2 cylinders after I put the wiring back behid the rectifier. I have another rectifier, wiring harness and cdi coming, but I will certainly explore some othe roptions before I go and put all this new stuff on. I didn't do anything to the bike except look at the fused/toasted connection. Man, that thing got hot!

 

Check the MAIN Ground.

Even if its TIGHT ... there can be a real problem if the Eyelet is corroded.

I'd clean that up ... just for Shidts and Grins.*

*Another defeat of the "Auto-sensor" system!

 

I'm having an issue with my bike not charing the battery at all. I checked the voltage of the battery with the bike off and it reads 12.5V but when i crank up the bike the voltage does not increase to charge the battery. I just replaced the alternator brushes hoping that was all it was but no luck still not charging. I just ran the voltage regulator test with two multimeters and neither meter showed any increase in voltage when reving the engine over 2000rpms. The red wire off the regulator shows slight melting at the plug end to the wiring harness. I'm guessing the regulator is fried, what do you guys think?

 

MGM...If you are not going over 12.5V, then your regulator is fine. However, not going over 12.5V when over 2000rpms indicates that your alternator is not charging the system. If changing the brushes did not work, you may have a bad stator and will have to replace that. FIRST, check the wiring from the alternator to make sure it is all in good condition. Then time to look for another stator for the alternator.

 

That would be a good guess.

You ought to be able to find one without any trouble. The Voltage Regulator is an Outsourced Part that is Common to a wide range of Models over a number of years.

Scoop-up a used Regulator and plug it in. If you show a bit above 14-Volts (14.2~14.5 @ +2K rpm's ) you're back in business.

 

A bad regulator can cause the alternator to output 0 volts.

The way the system works: Current is run through the rotor causing a magnetic field. Because the rotor is spinning it induces a current in the stator.

The voltage regulator controls the voltage on the rotor which adjusts the voltage out of the stator.

Stator seems the least likely thing to be bad - it pretty much just sits there. AND, since it has 3 outputs you'd need 3 failures in it to get the output to 0.

I'd pull the plug for the rotor. Check the resistance of the rotor and make sure it is in spec.

Then, check harness side of the plug. With the key on measure the resistance from the teal wire to ground, should be pretty close to zero. If it is open pull the connector off the regulator/rectifier. Measure the resistance in the teal wire from the alternator plug to the retulator/rectifier plug - should be 0. If not, there is a break in the teal wire.

Ok, the harness side of the rotor plug again. With key on check voltage from brown wire to ground. Should measure 12.5 volts or so. Just for grins measure the resistance from the brown wire to the + battery post. Resistance should be very low. If it's more than an ohm or so you've got a problem with power supply to the rotor.

Everything ok so far? Measure the resistance of the black lead on the regulator/rectifier to ground. Should be 0. If not, you have a problem with the ground for the regulator/rectifier.

Everything OK so far? Starting to look like the regulator/rectifier.

Does the headlight come on when you start the bike? If so, I think it's actually the rectifier that is bad.

Last check, plug everything back in. Find a way to get a test lead into the teal wire (at the back of one of the connectors). Start the Motorcycle. Put your voltmeter on the battery. With the bike idling ground the test lead you've got into the teal wire. Voltage come up? If so alternator is working, replace the regulator/rectifier.

 

This is why having a Known-to-be-good Voltage Regulator is swapped-in for one suspected of being bad.

Testing is reduced to running the bike up to 3-Thousand Revs a minute and Monitoring the Voltage. If Charging Current happens you're done in under 10-Minutes.

If NOT ... you go looking elsewhere.

Even the prescribed Regulator Testing, using 2-Meters, is seldom done when a Plug-In Test reveals whether the Unit is or isn't seeing a Current load from the Alternator, Generator, Dynamo or what-have-you.

But, that doesn't mean you can't have a Multi-Meter Festival if you really want too.

 

Well I think i found my problem, it's our good friend Corrosion! Along with the corrosion it seems the wires got a good jolt of juice somewhere along the way, the connectors were black and brittle. Evidently this was a problem for the PO as the original 3 wire connector was gone and the wires had been re-spliced and taped together. I found this when I was looking for the 3 wire connector from the stator to the wiring harness so i could check to see if the stator was putting out any juice. My question now is of the 3 white wires that come from the stator, can I connect any of the 3 wires from the stator to the 3 wires in the wiring harness? Or do they need to be in the correct order?

And yes that's the original fuse box, although 2 of the fuses have been re-wired into inline fuses but they are tucked away under the rear of the tank so you can't see them in this picture. Just need to order a nice new box to redo the whole mess.

 

That'll do it. The heating was probably because of the resistance due to corrosion. Somehow I missed that in my troubleshooting routine. Shouldn't have, you're not the first one with this problem.

On the white wires from the stator to the harness: Any-> Any. AC current between any two. It's all the same no matter how you hook them up!

Looks to me like you may need to clean the wires back a bit. You might need to put an extension in there. I'd solder them, then seal with liquid electrical tape.

FOR ANYONE READING THIS: This is stator to harness. Hook any 2 stator wires together and you will cook something!

 

you, my friend, have one of those electrical nightmares. Before you ever fire that up again, that harness needs to be cleaned up and SOLDERED. Do not use any crimp connections as the vibrations of the bike will loosen them over time. Crimp connections are also very prone to corrosion and then you will have a repeat. Clean all the connectors and apply a dab of dielectric grease to all of them. This will also help keep moisture out of there.

Good luck

 

Well i fixed those 3 wires today and i'm finally getting a charge from the alternator, but I still have some work to do looking for loose, corroded, or burnt wires. When i first started up the bike after fixing the stator wires, i still was not getting charge to the battery so i started poking around at the reg/rect and TCI connections. I guess I found a loose connection on one of those because when i checked the voltage at the battery i was finally getting juice from the alternator! I feel fortunate that my corroded and burnt stator wires didn't cause my regulator to get fried. I've got the battery on the charger so i'll take it out for a spin tomorrow and see how it goes. And for those that need to know, i did solder those wires together and temporarily wrapped them with electrical tape. I have some liquid electrical tape to apply to those wires to finish off the job. Next on my list is more and more wires to fix, and oh yeah replace the stock fuse box.

Thanks for all the info and advice, as usual you guys are on your game!

 

I kinda like heatshrink better than liquid tape but, thats what makes the world go round!!??

Different strokes for different folks!

Guess that's why I ride an XJ and not a hog

 

I vote Heat-shrink; too.

 

Environmental heat shrink is your friend. Use it anywhere out-of-doors to protect connections.