79sf Electrical Help, Please

[Shuriken]

In my testing I have found some interesting things and apparently caused some problems.

Now I can't get ignition coil #1 to fire. I've tested the coils. When I connect coil #1 to coil#2's input wires, I get spark. It seems only the side of the ignition that controls coil #2 is working.

I've got a bunch of problems with the bike electrically, but I need the engine to run so I can diagnose the other problems.

I got a replacement voltage reg/rect unit and will soon get a headlight relay, so I have some things to try, but I need spark, now.

What I want to know is how much voltage should be present at each coil input? Also, how much AC generator voltage should be generated on the white wires and yellow wires?

The coils receive their input from the TCI unit. It's possible I have a bad TCI. But it's also possible I have bad wiring, too. But how much voltage does the TCI send the coils when the key is on and the engine is not running? And how much voltage should the the coils get from the generator?

Thanks,
Ben

[randy]

OK, Ben.

Let's start with the coils.

The coils get direct battery voltage through the ballast resistor when the key is on. The ballast resistor drops the voltage to about 10 - 11V DC.

The coils are then connected to the TCI. In the TCI, the switching in the TCI GROUNDS the coils. Abruptly breaking that ground creates the spark.

Visit my website for a simple test of the TCI and Pickups. You won't have to disconnect anything to do this test and it will verify that your pickups and TCI are (or are not) working.

Randy's XS11 page

The white wires from the alternator should give you around 5V AC EACH WHILE RUNNING ABOVE 3000 RPM. This can be tricky to test, have the meter set right.

Let us know what you find

[Shuriken]

Well, thanks all for the help. I have not found the problem yet. I still cannot get spark out of coil #1 so I can move on to other problems.

As per Randy's web page testing procedure, at the disconnected TCI connector, I connected the meter between orange and black, and then gray and black and tested each separately. With the key on, voltage is 11 volts on each. When cranking, the voltage drops to 8 and alternates between 8 and 11. I would think this indicates that the pickup coils are good. I also tested OHMS for each pickup coil and one was 749 ohms and the other was 772 ohms, with the Yamaha factory manual stating 750 ohms. Unless 772 is out of spec (taking into account variance allowance), I think the pickups are good.

The ballast resistor tested at 2.1 ohms, with factory manual stating it should be 1.6 ohms. This seems to be outside of tolerance, but bypassing the resistor does not produce spark on the #1 coil.

My problem seems to be isolated to the orange wire feeding coil #1. If I connect coil #1 to the gray feed wire, I get spark out of coil #1. If I connect the orange wire to coil #2, it ceases to spark.

The red/white wire that feeds both coils shows 12v when the key is on. I cannot determine voltage on either the gray OR orange coil feed wires while cranking the engine.

I tested continuity between the TCI unit connector and the orange bullet connector at the coil and also the gray bullet connector. I have continuity, so I know there is continuity between the TCI and coils on those wires.

Per factory manual test procedure on page 6-11 under TCI voltage checks, everything checks fine except for #3 test, which tests for voltage between the black/white wire and ground, and which should be 6v. I have 0 volts.

I did not have time to check AC voltage from the generator, but I checked it a week ago on the yellow wire and it was around 5 volts AC while turning the engine over.

So, these checks should point me to the problem circuit but I need help interpreting the test results.

As I mentioned above, I should get 6v on black/white to ground and get no volts. The wiring diagram shows the black/white wire as going to the emergency stop switch. If I bypass the switch I then get 12 volts at the black/white wire to ground and the manual states I should have 6.

What gives?

Ben

[Shuriken]

Now I have to correct myself in clarification.

I mentioned I used Randy's test procedure on the TCI. Well, I did it wrong. I went out and tested correctly (with the TCI connectors connected normally to the unit) and fed the multi-tester leads in between the blades and plastic. I said I got 0 volts between the black/white wire to ground. But with the connectors connected, I see the 6 volts. I also get 11 volts on both orange and gray wires. However, I noticed a difference while cranking. The gray (good coil) wire varies between 11 volts and 5 volts when cranking. The orange (bad coil) wire only varies between 11 volts and 8 volts.

I also tested the pickup coils again with my digital multimeter and found that pickup coil #1 is 746 ohms and coil #2 is 770 ohms. Earlier I misstated that factory manual states 750 is acceptable. The correct acceptable value per my factory manual is 720 ohms + or - 20%. So by my figures the pickup coils could vary as high as 864 ohms and as low as 576 ohms.

So with my above testing in mind, it appears to me that the voltage is not dropping enough on coil #1 to produce the spark, right? Yet pickup coil resistance seems to be within tolerances. If insufficient voltage drop is the problem, how do I fix it?

Are we getting close?

Thanks,
Ben

[randy]

Ben, you are very close.

It sounds from your testing that the TCI is working, although it may need the "solder fix", which is also explained on my web page. There are three failure points between the coil and the TCI:

1. Bullet connector at the coil (Gray or Orange)

2. 8-pin connector on the TCI

3. Inside the TCI, on the circuit board where the TCI connector is soldered to the board. This is accesible by removing the cover, no need to even remove the TCI from the bike.

The fact that the TCI is swinging the voltage is a good sign. I know this is a tired theme, but what I would do at this point is take apart the orange terminal at the TCI plug and either solder on a new one or carefully remove the old one, clean it up and re-solder it on. Crimp the ears down so it makes a tight connection on the TCI pin. Take a 1/2" off the wire so you're sure have good continuity. Do the same at the coil end on the orange wire. Clean all of the other pins and the pins on the TCI.

Then remove the fuse block plate. Behind it is an inline connector that connects the pickups into the wiring harness. It's the four-pin one. Clean all of the pins and sockets. The pickups put out a very small voltage, so any corrosion here can cause problems.

Because I'm anal about these things,what I would do next is reset the gap at both pickups. You see, any help you can give the pickups to put out a stronger signal will make the whole ignition system work better, ie hotter longer spark. The gap is the key. The recommended gap is .7 millimeters. I have mine set at .5 and she starts with just a touch of the button hot or cold.

If you do all of these things, I'll bet you'll be running in no time!

[Shuriken]

Randy,

I went through the wiring. Cleaned all the pins again, moved wiggled wires, etc. Nothing. Again. Nothing.

Inserted a spare spark plug in coil #1 lead, grounded it, and cranked the engine. Then I pushed on the wiring near the TCI while cranking and saw a spark.

Couldn't get it to return so I cleaned and checked all the pins again, and with the bike gutted, I was able to get spark. I carefully put everything together, rode it around the block.

Got back into the garage and lost spark on #1 coil again. VERY frustrating. That's the status now.

I am not sure what to do at this point because all the connectors are clean. I made sure they all fit snug as well. I think at this point I am going to cut the connectors off the bike and permanently solder the wiring. If I remove the engine at some point or something like that, I can always resolder.

I know I can buy some replacement connectors but at this point I don't know if I trust them. Mine are all cracking and crumbling at this point, whether or not their condition has anything to do with the bike's problems.

The only good thing that came out of all of my time yesterday is that I found the problem that was causing my oil/brake/tail light to flicker, even though I knew I had a good brake light and oil pressure. I found 2 bullet connectors I thought I had cleaned once before - coming from the rear brake switch - that were rusted and corroded badly. I cleaned them up shiny and the oil/brake/tail light warning bulb no longer flickers on.

Also, in trying to troubleshoot the tachometer, the manual says I should have 5~7v AC between the white and black wires from the main harness, and 12v DC between brown and black. Well, I have 12v DC between brown and black but well over 12v AC between white and black. My factory manual does not indicate a flowchart procedure for overvoltage - only for situations where AC is less than 5~7 AC or not present. = Thoroughly confused about that.

So here I am again. But I'm going to get nasty and make some permanent connections....

My headlight still does not work. A guy in another post mentioned an auto relay for the headlight? Hmm...

Ben

[Shuriken]

Today I soldered wires to bypass the plastic connectors where the pickups connect to the main wiring harness. I did the same at the AC generator connector. I can always solder in new connectors or the old ones, but I wanted to eliminate those points as problems.

However, doing the above did not produce spark again in #1 coil.

Also, I checked/set the pickup gaps. Still no spark on coil #1. I know both coils are good because switching the gray and orange wires in separate tests produces very good spark on both coils. It's just the orange wire for some reason.

I've also tested pickup coil resistance and they seem to be within tolerances so I think they are working.

Bypassing the ballast resistor produces no difference in results.

So I think I have eliminated from the problem:
- the pickup coils
- pickup coil gap
- the ignition coils
- the ballast resistor
- pickup coil quick connector (eliminated)

The only thing that's left should be the wiring and connectors between the TCI and ignition coil, and the wiring between the pickup coils and the TCI unit, and/or the TCI unit itself.

I can't test the TCI unit other than what we have. It would be nice to swap it on to another XS11 to see if the problem duplicates.

I have another wire harness coming that I can use or that I can use plastic connectors from. In the meantime, I think the only thing left is the wiring/connector right at the TCI box and/or the wiring/connector at the ignition coil.

I did the solder fix on a TCI unit I had a year ago and it worked fine. I resoldered this TCI box also. I had a spare kicking around I was going to send off for repair and lost the box.

One thing I am absolutely sure of after testing voltage is that on the gray wire at the TCI box the voltage is going from 13 down to around 6 volts and I can watch the needle show the field coil breakdown that causes the spark. On the orange wire the voltage drops but not low enough. It is indicative that the field coil is not dropping out on the orange wire for some reason.

What causes the field coil to drop? The TCI unit or the design of the ignition coil? I think therein lies my problem.

I still don't know why I am seeing 15v ac on the wire to the tachometer when I should be seeing 5~7v....

Ben

[LoserShoes]

AC volts can be kinda hard to measure sometimes, depends on what your meter is measureing. Some measure peak, some RMS, and some average. RMS is the most useful. Your can, and probably are picking up noise which throws it all off anyway. The best way is with an oscilloscope, but you probably don't have access to one.

Basically if you are measuring any ac your probably ok there.

[DiverRay]

Ben;
Go back to what Randy was trying to tell you. The TCI has a few screws holding the cover on. take off the screws and cover, and re-solder all the wire connections on the board. From what you have said, you have one wire that may be broken internally.
Check the wires with an ohm meter from the TCI, with the cover off, to the "bad" coil. If there is no continuity, work your way back one connector at a time to the TCI box. This should take less than 10 minutes. I would bet that the problem is inside the TCI, just a bad solder joint.

[Shuriken]

Thanks everyone for the help. Thanks diverray for the reply.

I have done everything mentioned and have still come up with no spark. I have continuity from the pickup coils to the TCI unit, and from the TCI unit to the ignition coils, including the non-firing coil. I have resoldered the connections on the TCI board. I have taken the screws off and tested continuity from the solder connections to the ignition coils and have continuity. I have tested the pickup coil resistance ratings and they are within limits. I can produce spark on both ignition coils with or without the ballast resistor in place.

Anybody wanna take my 79sf TCI box and test it on their 79sf to see if the problem is reproduced? Unless it's a TCI unit problem I've definitely missed something. Until then, I still have no spark and can't ride.

Also, thanks Losershoes for the info. It is possible my meter is measuring 7.5 volts AC on one side of the wave and 7.5 on the other side of the wave for a total of 15v ac. But the generator output seemed to be correct for each winding when I measured AC output, so I really think my tach could have burned out from being fed 15v AC. Even if I get a replacement, it may blow too.



Ben

[Shuriken]

I have the TCI guts in front of me. I would like to test the transistors. Maybe I can get a working replacement TCI somewhere but for now, how should I go about testing the board?

Ben

[Shuriken]

Got a known-good loaner TCI from a great guy (thanks Buck). Plugged it in and what 'dya know - no spark.

At that point I was chapped but I had a spare 79sf wiring harness I bought a month ago or so. Spent a bunch of time today to swap it in and the existing one out. In the end, I plugged in the loaner TCI and got spark. I rode the bike around the block.

So - whatever it was, I never found it, but it was in the wiring of course. I had gone over and over the connectors, testing, etc., and couldn't find anything.

I still have no headlight and no tachometer. I'm right back where I started testing before when spark vanished. Hopefully I can find and resolve the headlight / tach problem without killing spark again.

I have only 3-4 volts AC to the tach where the manual says should be 5-7. Might have a weak ACG output or ... gasp ... crappy connections.

Here we go again. Any advice is helpful. By the way, if anybody has a 79sf and can look at the wiring by the fuse panel for me ... There are 2 wires to complete my harness swap that I'm wondering about.... one comes out of the harness and heads to the fusebox area - it is only a single bullet connector - red with a yellow stripe, male connector. What does it connect into? Also, the thicker green wire (female bullet) coming off of the big relay to the left of the fuse panel - where does it go?

Ben

[Shuriken]

Well, I dug up a grand total of 3 headlight relays. It turns out that 2 of them were bad. So now I have a working headlight. Each relay clicks when the engine starts to run, but only 1 actually works. Perhaps I could dissasemble and clean the other two somehow...

This far in the game I did not think I had an A.C.G. problem because of the testing I performed. I had 12-15+ VAC on each winding output and charging voltage was 14-14.5 VDC. That's when I discovered the relay problem. Sometimes you get spare parts that are bad.

So far then, I have replaced a wiring harness, a voltage regulator/rectifier (although I haven't determined %100 if the old one is bad), and a headlight relay.

For those still reading this ream, my tachometer still does not work. Most recent test shows 12 VDC where it should be but only 3-4 VAC where I should have 5-7. Not exactly sure how accurate my testing is. It would be great to be able to swap with a known-good loaner to see. But alas, I don't have a spare. Most of my spare parts went with the 80g when I sold it. Not even sure if an 80g tach would work on the 79sf.

I still can't figure out (near the fusebox) the red wire with a yellow stripe (male bullet) coming out of the wiring harness. Not sure to which other connector it is supposed to be connected to. And I don't know where the fat green wire (female bullet) coming from the starter relay should connect to. Those two items and the tach are all that's left for now.

Ben

[TopCatGr58]

Hey Ben,

You didn't say if you used an exact same model/year wiring harness as your 79SF? The Red with yellow striped wire is supposed to be the main power from the fuse block to the headlight relay, however you've got headlights now with that wire NOT connected!?

According to the wiring diagram, the only green (dark)wire is the right turn signal wires. There's a light green wire that's connecting the Reg/Rect with the Alt.

Any year(78-81) tach will work on any XS, just that the plug may or may not be the same due to fuel gauge/light differences.
T.C.

[Shuriken]

Headlight died again. Has anyone replaced the headlight relay with a standard el-cheapo replacement?

I replaced my old tach with an ebay replacement and my tach works. I think my ACG is good but have been fighting with a bad tach and bad relay.

Ben