Electrical nightmare

[MArk Jensen]

So... first time posting, but you all have helped a lot in past projects, so thank you. I have a 1979 XS650 special. And I have some serious gremlins in the electrical system. The most obvious being the battery doesn't charge. So I pulled the rectifier from under the battery box and gave it a test, sure enough it was bad. I also did the "slap test" and that came back good. So I ordered a new tectifier from mikes and put it in. Still did not charge. Pulled the rectifier again and tested it, it's still good but had a lose connection. Got better terminal connectors reinstalled it all and fired it up. Now this is where it gets interesting. The neutral light that I thought burnt out a month ago came on for about ten seconds and then went back out. And my left blinker only wants to work sometimes now, and the brake light on the dash is always on, and my headlight doesn't want to work. I found all this out of course during my test ride after I had the battery on the charger. Stopped for gas, and it didn't have enough charge to turn it over. I was close to home, so I kick started it and got it back, however it completely died coasting into my drive was, "the only good luck I seem to of had". So... now I'm out of ideas. Any help would be appreciated!

 

[DanielBlack]

Mark, it seems like you have more than a few Gremlins. Have you gone through every connector on the bike? Clean, shiney, tight? Have you done continuity tests on every wire in the harness? With all those various intermittent problems, I'd concentrate on the common denominator first; the harness and all its connections.

 

[xjwmx]

I've often thought it would be good to get one of those complete harnesses from Mike's, especially if you were new to electrics. The old wires can break inside the insulation, the wire connection at the connector can go bad and look like a bad component, or worse yet be intermittent. I think daddygcycles makes harnesses too.

 

[MArk Jensen]

@DanielBlack, short answer no. I have tested the ones I have easy access to, others are completely buried. I just pulled the head light off and am about to test those. I'm a little concerned that I have a host of new issues after reinstalling a working rectifier. Do the three white wires coming off the rectifier and going to the stator need to be in a specific sequence?? The witting guide didn't say so.

 

[xjwmx]

Do the three white wires coming off the rectifier and going to the stator need to be in a specific sequence??

Short answer, no.

 

[DanielBlack]

No specific sequence for the white stator wires.

Sussing out your harness is most definitely your next step. Until you do so there are too many unknowns to successfully troubleshoot systems.

There are many threads that touch on this. Those, an appropriate wiring diagram, and a VOM are your best friends as you move forward.

 

[member3480]

Well first of all you need to test to see if bike is charging at all. Buying a REG/REC may only be one issue. Brushes could be bad or even alternator just bad. Grounds are also important. You need to buy or borrow a test meter put it on DC volts and hook it up to your fully charged battery. Battery should read 12to12.5 volts with bike off and when you rev motor passed 1500 rpm you should see the meter go up to 13.5 to 14 volts charging if not you need STATOR or ALTERNATOR. I had a bike do the slap test but still did not charge. Changed out both and all good.

 

[MArk Jensen]

I have a multi meter from Harbor Fright, but have not done to much testing after the new rectifier has been installed. I really wanted to take this on vacation with me next week, not sure she will be trustworthy by then.

 

[MArk Jensen]

Welp charged the battery, installed it, meter had it at 12.8. Started the bike let it warm up for a second, rev'd it up and the volts went down, let off the gas and it went back to 12.5. My concern is I have a more problems after installing the rectifier, I've lost continuity in my headlight, left blinker and neutral light, god knows what else,

 

[DanielBlack]

What became of your checking and cleaning of every connector? Checking each wire is solid and continuous? Each wire connected to where it should be? Until you rule out the 40yo wiring it remains highly suspect. In my experience, intermittent issues make wiring and connections doubly suspect.

My guess: You very well might have an issue with a charging component or two, but your loss of headlight and other lights prove the existence of problems in two separate systems. Best to start with fixes that might affect both. The wiring harness.

god knows what else,

Exactly. Start a methodical search to root them out.

 

[Mailman]

Mark, it seems like you have more than a few Gremlins. Have you gone through every connector on the bike? Clean, shiney, tight? Have you done continuity tests on every wire in the harness? With all those various intermittent problems, I'd concentrate on the common denominator first; the harness and all its connections.

What he said.
Often times , wonky , erratic and intermittent lights are suffering from bad grounds , corroded connectors, broken or pinched wires or all the above. You won't know until you get in there. Start at one end and work your way to the other. It's tedious but necessary.

 

[fredintoon]

Hi Mark,
you didn't say how badly has the dreaded PO treated the bike's wiring harness.
While much of the wiring is plastic-wrapped every connection onto every mystery module can be got at to be cleaned, inspected and re-assembled.
OTOH if the dreaded PO has cut the harness open and meddled, you could be in a world of hurt.
Note that the stock rotor is an electromagnet. Do an Ohms reading between the rotor's slip-rings.
If there's LESS than 5 Ohms resistance the slap test will still work but the rotor will suck more power out of the battery than the alternator puts in so there's nothing left to charge the battery.

 

[MArk Jensen]

Luckily the previous owner didn't do anything to the bike. It only has about 17,000mi on it. I'm curently looking at a wiring diagram, and formularizing myself with it. I will definitely check the slip rings when I get back from vacation. God Bless America.

 

[Bob Kelly III]

I would suspect the brushes in the alternator, when they go bad they quite often take out the rectifier because the terminals often touch ground periodically,,, which means it will take out the Rectifier again if you don't make sure the Brushes in the alternator are long enough to work properly... they ware out over time and need to be replaced .
it's obviously not charging now ...
there is a technical reference section here under.... forums/Garage/ xs650 technical reference with a real good section on electrical problems
check it out !
.....
Bob......

 

[MArk Jensen]

The brushes are about 1/2 to 3/4 of and inch long. How long should they be? I found a great electrical diagram what shows what each electrical connector goes to.... so now I know why I'm testing.

 

[member3480]

OK well you are not charging. Now you have new REG/REC so its either the rotor or the alternator
What are you running POINTS / TCI / PAMCO ????
You are right in NY I do have a spare test alternator from a 1980 without plug so you would have to match up the colors and push the pins on your plug (it has push pins on end) I use it to test bad bikes like yours. I can ship it to you on Monday if that would help. That way you know if alternator is bad. If you want to try it PM me your address and if that fixes it tape it up go on your vacation and you can send it back when you come back. If it doesn't work then yours is good and you need a rotor . I have had a rotor do the slap test but not charge NEED 4 OHM or more or bad.

 

[MArk Jensen]

2.5 OHM on the rotor, think I found the major problem gentlemen. I know I have a couple other bugs to stomp out, but found my major issue.

 

[MArk Jensen]

Ordered rotor and puller from Mikes XS. Just put them in and still getting about 12.8 when rev'ed up. I know the rotor was no good and I know the rectifier was no good. I guess I need to keep crossing things off the list. Any suggestions on what I should be looking at next?

 

[5twins]

As long as you're getting some voltage increase when revving and you have the original mechanical voltage regulator, it may need to be adjusted. Here's some info .....

Even if that works, I still recommend replacing that antiquated unit with an automotive one. The output is all over the place with that old original. The auto unit will give you a nice, steady output.

 

[retiredgentleman]

Previously you said the slap test was good. Perform that same test again, and confirm that the rotor still produces a strong magnetic field.
If the slap test is good, you can test for AC voltage at the 3 whites wires coming out of the alternator. Select AC volts on your VOM. You can push your 2 meter probes into the back of the plastic multi pin connector. Test the 3 different combinations of white wires while the engine is idling at 1200 rpm.
There should be around 12.5 to 13 volts AC. If you see that, you can also rev the engine and watch the AC voltage.