Intermittent loss of power

[CatatonicBug]

Where would you put the probes to check the voltage at the coils with the motor running - one on the orange or grey and the other on the red/white...?

That's what I did.

[dbeardslee]

That's what I did.

Is that where you got the 10.6 volt reading?

[CatatonicBug]

Yes, but not while it was running. The 10.6v was measured while NOT running.

[dbeardslee]

You might want to think about taking your battery to an auto parts store that has battery test equipment and get 'em to hook it up. They can do a more comprehensive test than what you can do at home, and given that the acid level has gotten low and the five second recovery time when you load tested it... JAT

[CatatonicBug]

You might want to think about taking your battery to an auto parts store that has battery test equipment and get 'em to hook it up. They can do a more comprehensive test than what you can do at home, and given that the acid level has gotten low and the five second recovery time when you load tested it... JAT

The "recovery time" isn't the battery. There is a relay somewhere that clicks, changing the voltage. I put the battery on a trickle last night, and the charger was green this morning. I left it charging all day, and will check voltages again tonight. I will likely just go get a new battery this weekend (after pay day), since I know the one I have has been at least slightly compromised. Its a few years old anyway, so its due to be replaced. I did buy a plug wire set, and had to order the NGK screw-on plug caps from ebay (Oreilly wanted to charge me an extra $13 to ship them in from CA!). I'll get that installed when the caps arrive.

[dbeardslee]

JOOC - what kind of plug wire set did you get?

[CatatonicBug]

The one you suggested earlier - Omni-Spark 4-cyl version.

[CaptonZap]

This is what CBug said - "voltage on coil wires at the TCI, key on, not running: 10.6v" Could it be that the coils just aren't getting enough juice from the TCI to fire them reliably? He doesn't have the 1.5 ohm coils - he's got 3 ohm Accel coils, and even the stock coils on an '81 are 3 ohms, if that makes a difference. Where would you put the probes to check the voltage at the coils with the motor running - one on the orange or grey and the other on the red/white, or just red/white to ground?

What I was trying to show was that in the early TCI's, the voltage to the coil after the ballast resistor is lowered, after the starter bypass was turned off. The stock coils use around 9 V, if I remember correctly, when running.
The Accel coils may require a full 12 volts for good output. IDK. The no voltage at the grey wire, when running, indicates that the grey wire is shorted to ground, either external to the TCI, or internally, or the coil or grey wire is opening up between the measuring point and the input to the coil. The fact that it seems to be heat related would argue for the coil winding, or, if that is not the case, a short in the power transistor in the TCI.

With the engine running, from the R/W to ground at the coil should read battery voltage or close to it, if there is no ballast resister. From the grey or orange to ground, while it is running, you should get the voltages CBug measured.
CZ

[CatatonicBug]

I took a few more readings tonight. I put the battery on a charger for about 20 hours. It had dropped to trickle by the time I got up this morning, but I left it on till this evening.

Right after removing the charger, the battery read 13.6v
2 hours later, the battery read 12.82v
At that point, the gray and orange wires at the TCI both read 10.96v

Started the bike, and the problem is still there, cold, so it's not heat related.

Red/white @ idle: 13.6v
Red/white @ 2k+ rpm: 14.2v
Red/white with engine stopped: 11.6v
Battery still read 12.8v

One thing that is twisting my brain a bit - the gray and orange wires at the coils are negative leads, while the red/white is positive. At the TCI, all 3 are positive? I get the readings by putting the red lead on the gray or orange wire, and the black lead on the negative battery terminal. However, if I reverse the leads, and put the black lead on the gray or orange wire, and the red lead on the positive battery terminal, I get 0.96v. How is that possible??

[dbeardslee]

I'm still wondering where the voltage is going to. You're supposed to get a reading of 12V at the TCI, and where you had been getting 11.2v now you're getting 10.96v if I'm understanding you correctly. And with 12.82V at the battery that should certainly be enough to give you a 12V reading at the TCI. It seems the voltage on the battery has gone up since your first test, but the voltage showing at the TCI has dropped. Too bad you don't have a spare 4R0 TCI to either confirm a problem with the TCI or eliminate it.

[TopCatGr58]

One thing that is twisting my brain a bit - the gray and orange wires at the coils are negative leads, while the red/white is positive. At the TCI, all 3 are positive? I get the readings by putting the red lead on the gray or orange wire, and the black lead on the negative battery terminal. However, if I reverse the leads, and put the black lead on the gray or orange wire, and the red lead on the positive battery terminal, I get 0.96v. How is that possible??

Hey Bug,

It's late, but I wanted to "try" to answer this. Okay, basic electrical DC current, starts at power source=battery + terminal...then goes thru wires to the LOAD source....then back to the battery via the (-) terminal. But the (-) terminal is still carrying voltage/power/electricity....it's just that it's usually a bit LESS than right at the battery because some of it is being used by the "LOAD" device. The Spark Plug coils are a very densely wrapped COIL of wire....the 12V's goes into it via the Red/White wire....then because there is so much wire/distance...it generates a load and resistance(3 ohms), which will drop the voltage some when it finally comes out the (-) terminal on it's way back to the battery.... but it's really still (+) Voltage....it's just being measured now AFTER the load device, and with the circuit still connected all the way around....when you tap into the (-) side of the coil....you are still able to read (+) voltage....but should be less since it's after the load source....the COIL. Isn't Electrickery fun!?

T.C.

[CaptonZap]

One thing that is twisting my brain a bit - the gray and orange wires at the coils are negative leads, while the red/white is positive. At the TCI, all 3 are positive? I get the readings by putting the red lead on the gray or orange wire, and the black lead on the negative battery terminal. However, if I reverse the leads, and put the black lead on the gray or orange wire, and the red lead on the positive battery terminal, I get 0.96v. How is that possible??

Look at it this way. The red wire comes off the battery + post, so it is positive in relation to ground. The red wire goes up to the switch, changes to brown and back to the fuse block, and at that point, it is still positive in relationship to ground, (PIRTG). At the fuse block, it changes to R/W, and is still PIRTG. The wire goes to the TCI, and also to the coil terminal, through the coil, and comes out at the grey terminal, and at that point, it is still PIRTG. The grey wire goes to terminal one on the TCI, and the potential there is still PIRTG. All of this is with no current flow. The R/W wire is feeding the TCI, the Gry and Org are the end of a continuous circuit from the battery + post, so they are still PIRTG. As soon as the engine runs, they become a pulsating extension of the battery neg post, or ground. At that point, they are neg in relationship to the R/W wire at the TCI. Until the engine runs, they are at the same potential (volts), as the R/W wire, PIRTG.
To look at it another way, until the engine runs, the Gry, Org and R/W wires, at the TCI, are just three legs fed off of the kill switch on the handle bar.
All of this makes a little more sense if viewed with a colored wiring diagram, so you can follow along the R/W wired road.

All of the above is predicated on an 80G wiring diagram, and may or may not bear any resemblance to an 81 color code. (My lawyer made me type that)

CZ

[CatatonicBug]

Ok, I think I get it...

Now, back to our regularly scheduled program.

Just now, 4.5 hours after removing the charger, the battery reads 12.4v with the key off. 12.2v with the key on. And all 3 (gray, orange, and red/white) at the TCI read 11.2v with the key on, not running.

So, I guess I'm losing a full volt somewhere, but that really doesn't explain why I'm not getting power to the gray wire while running.

[CatatonicBug]

As suggested earlier, I just checked the ohms from the gray and orange wires to the Black wire in the TCI plug (also tested at the negative battery terminal). I get 18 ohms on both. I guess that means they are both shorting to ground?

[CaptonZap]

As suggested earlier, I just checked the ohms from the gray and orange wires to the Black wire in the TCI plug (also tested at the negative battery terminal). I get 18 ohms on both. I guess that means they are both shorting to ground?

I take it that this was with the TCI connecter out, but in that case you should not have had any sort of reading back to the battery, since the black ground wire to the TCI was disconnected . Huuum. Unless there is an internal ground to mounting lug on the TCI that the early TCI's did not have. Or are you saying that you measured the wireing end of the TCI connection? Measuring that would be measuring the circuit resistance back through the coils and ignition wiring.
With the 8 pin connecter out, measure the resistance between the grey and black terminals on the TCI. You shoud have NO reading on either the grey or orange to black.
It sounds more and more like a faulty TCI.

CZ