Intermittent loss of power

[dbeardslee]

The light bulb use is mainly for automotive (12V) bulbs. However, it works GREAT on 120V bulbs too. I do agree that regular maintenance that includes flushing and re-application would be a good idea though. You never know what kind of conductive boogers might get caught in the stuff.

Reason I keep mentioning the voltage test at the TCI is because of what I noticed when I redid all my connectors on Betsy. I had voltage about what you're showing before I started, and I'd recheck the voltages after redoing connectors. I got a tenth of a volt here, and two tenths of a volt there, and by the time I was done I was up to the full 12v at the TCI. If you're back up to 12V after cleaning that connector you might be able to use the TCI voltage test as a yard stick for measuring when it's time to redo the dielectric. JAT

[CatatonicBug]

Good idea. I'll take a look at it.

[CatatonicBug]

Problem is back, this time, reliably.

I extra-cleaned the midway connector, but the problem persists.
No spark on plugs 2&3.

All of this is with a hot engine.

Voltage at the battery with ignition off: 12.2v
Voltage at the battery while cranking: 10.6v
Voltage immediately after cranking (not running): 11.8v
Voltage 5 seconds after cranking: 12.2v

Pickup coil ohm readings:
Ohms from the midway connector, through the pickups and back, key ON: 780 & 812
Same reading, with key OFF: 805 & 810
Ohms fron TCI 4-pin connector, key on: 760 & 807
Same reading, with key off: 807 & 807

Voltage on coil wires at the TCI, key on, not running: 10.6v

I do realize that the voltage on the battery is a bit low, and is likely due to the fact that I let it get low on water over the summer. However, I don't see how that would be giving me the symptoms I am seeing, just losing spark on ONE coil.

These were measured both at the TCI and the coil connectors:
Ohms on red/white wire: 0 ohms
Voltage from the TCI to coil 1&4 while running: 0.3 to 2.0v (the higher the rpm, the lower the voltage)
Voltage from the TCI to coil 2&3 while running: 0v

I don't know, but after all of this, it really seems that the TCI is just deciding not to send voltage to the gray wire to feed the 2&3 coil.

[dbeardslee]

Voltage on coil wires at the TCI, key on, not running: 10.6v

The TCI requires a minimum of 10.5V to operate properly. According to 3Phase, as the voltage approaches 10.5V it will run, but "it won't be happy."

I would go through and clean all the connectors and see if you can recover the voltage that's being lost between your battery and the TCI.

I'm betting on a bad battery or connections robbing voltage, or a bit of both.

[bikerphil]

I extra-cleaned the midway connector, but the problem persists.
No spark on plugs 2&3.

Did you extra-clean the 4 wire connector at the TCI?

[CatatonicBug]

Did you extra-clean the 4 wire connector at the TCI?

Yes. The only thing I have not done is replace the metal terminals on the wires.

[CaptonZap]

Problem is back, this time, reliably.


Voltage from the TCI to coil 1&4 while running: 0.3 to 2.0v (the higher the rpm, the lower the voltage)
Voltage from the TCI to coil 2&3 while running: 0v

I don't know, but after all of this, it really seems that the TCI is just deciding not to send voltage to the gray wire to feed the 2&3 coil.

I have not reverse engineered an '81 TCI, but from the DaVinci pictures I have seen of the boards, the two ('80 and '81) TCI's were alike in the major components and the way they were engineered. With that said, and drawing on the schematic of the TID-14, (2H7-10), the grey wire from the coil to the TCI is what completes the circuit through the primary from the red/wht wire on the coils, (12V+), to ground, thereby building a magnetic field in the coil. The current flow is FROM the coil through the grey wire to the TCI, and it gets grounded inside the TCI. When the TCI gets a pulse from the pickup coils, it breaks the ground, by shutting off current flow through a power transistor. The reason you get a voltage reading on the grey wire from the coil, when running, to the TCI, is that the current is not flowing constantly, but in pulses. Your meter is taking an average, if you will, of the voltage pulses present. The more pulses per unit time, the more number of electrons get through, and the voltage, (pressure in the wire) goes down.
Imagine a hose, (wire), water in the hose, (electrons) pressure on the water, (voltage), and a pulsating on/ off valve, ( rotating plate with holes in it), in front of the nozzle on the hose. The pressure is highest when the nozzle is closed. As the rotating plate starts to rotate, it lets some water through, and the pressure at the inlet to the nozzle goes down a little. The faster the plate rotates, the more water gets through, and the lower the pressure gets.
The fact that you get no voltage at 2&3 indicates that either there is no pressure, (voltage ) through the primary coil, there is a break in the wire between the coil and TCI, there is a bad connection some where between the measuring points, or the transistor or traces in the TCI are having a break down.
Substitution would be the quickest way to test the theory. An O-scope on the transistors terminals would be another.
Good luck, CZ

[bikerphil]

I replaced that connector with good quality one from geezer, and it doesn't wobble around in the TCI anymore. The old terminals were stretched and the dielectric grease in there didn't help any. My bike hasn't missed a tick since replacing that.

[CatatonicBug]

Very nice description CZ! I did notice that the gray and orange wires are negative, and the red/white is positive.

I did not repeat this test again, but I already tried switching the coils, and the problem follows the circuit, not the physical coil. So, at this point, we're pointing at a fault in the TCI somewhere?

[CatatonicBug]

I replaced that connector with good quality one from geezer, and it doesn't wobble around in the TCI anymore. The old terminals were stretched and the dielectric grease in there didn't help any. My bike hasn't missed a tick since replacing that.

No wobbling on any of the connectors. The individual terminal connections are solid too, since I manually pressed spade terminals into them to connect the alligator clips.

[CaptonZap]

Very nice description CZ! I did notice that the gray and orange wires are negative, and the red/white is positive.

I did not repeat this test again, but I already tried switching the coils, and the problem follows the circuit, not the physical coil. So, at this point, we're pointing at a fault in the TCI somewhere?

That would be my take on it. The switching transistor is getting hot and shorting out?
How long after it starts missing does it take to start running again, and do you have to shut it off and let it cool down before it will heal its self?
Here is another test you might try.
Leave the seat loose, so you can get to the TCI quickly. Take your meter with you, and go ride, until it misfires. Shut off the bike. Dis mount, remove the seat, unplug the TCI connector, and measure Ohms from pin 1 (grey wire pin) to ground (pin 8). There should be no continuity. If there is, it is definitely the TCI is bad. If there isn't, the TCI could still be bad, but be failing under running conditions, which would require you to set up a more elaborate test procedure than I think you want to indulge in. Find a know good one to swap.
If you try this test, let me know the results, please.
CZ

[CaptonZap]

For those following at home, without a program, the pins are numbered left to right, when looking at the TCI spades, top row left is one, next one right is two, and so forth. The bottom row left is 5 etc.

CZ

[dbeardslee]

I do realize that the voltage on the battery is a bit low, and is likely due to the fact that I let it get low on water over the summer.

How low did you let the water level get? If you let the water drop to the point that it exposed the plates it may have damaged the battery. Exposed plates will sulfate quickly, and once that happens the plates become inactive.

With it only showing 10.6V at the TCI my question for CZ, who seems to know a LOT about the way they operate is this - how is that low voltage going to affect the way the TCI operates?

[CaptonZap]

With it only showing 10.6V at the TCI my question for CZ, who seems to know a LOT about the way they operate is this - how is that low voltage going to affect the way the TCI operates?

The problem with low voltage is not with the TCI, but with the coils. The voltage to run the solid state circuits in the TCI is regulated down to 6 v, and I have run a '78-80 TCI down to 7 volts input, and it still does it's thing.
The 10.5 V that folks talk about, is about the minimum voltage that will drive the coils reliably, unless the ballast resister is removed, and the 1.5 ohm coils are fed directly from the battery. Next time you have your gas tank off, and are messing with the carbs, check the voltage at the R/W wire at the coils and see what voltage they are at with the engine running.

CZ

[dbeardslee]

The problem with low voltage is not with the TCI, but with the coils. The voltage to run the solid state circuits in the TCI is regulated down to 6 v, and I have run a '78-80 TCI down to 7 volts input, and it still does it's thing.
The 10.5 V that folks talk about, is about the minimum voltage that will drive the coils reliably, unless the ballast resister is removed, and the 1.5 ohm coils are fed directly from the battery. Next time you have your gas tank off, and are messing with the carbs, check the voltage at the R/W wire at the coils and see what voltage they are at with the engine running.

CZ

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?