Tci Test

[boyat68]

Recently I have read a thread on testing the TCI. I want to post the readings from my test following the test procedure outlined in the Yamaha Manual “XS 1100 Models 1978-1980 Service Manual.”

Battery voltage before test = 12.68 Switch off
Battery voltage before test = 12.05 Switch on
Battery voltage before test = 12.45 Switch off

4 - Prong Connector:
White/Red to White/Green:
No 1 pick-up coil = 750 ohms Book says 720 ohms +/- 20%
Yellow/Green to Yellow/Red:
No 2 pick-up coil = 753 ohms Book says 720 +/- 20%

TCI unit voltage checks
With all components connected

Switch on

Gray to ground =11.30v Book says 12v
White/Red to ground. = 11.11v Book say 12v
Black/White to ground. = 6.15v Book says 6.0v
Orange to ground. = 11.12v Book says 12v
Red/White to ground. = 11.13 Book says 12v

Battery voltage after test = 12.05 Switch on
Battery voltage after test = 12.42 Switch off
Battery voltage after test = 12.58 Switch off 5 min. later

Started Bike

Battery voltage = 13.20 with full choke
Battery voltage = 13.25 with half choke
Battery voltage = 12.09 after 5min with no choke

Couple of things to remember:
Batteries on our bikes are starting batteries; therefore they have very thin plates, and deliver their full load for just a few minutes and then charge back up with sufficient supply and regulation.
When you switch on the key, you have a large resistive load slurping up that amps/voltage satisfying Ohms Law, therefore the battery voltage drops and continues to drop as long as the key is on, and over time without the key on, parasitic drain will drop the voltage.

Lead Acid batteries have a voltage level fully charged of 2.2 volts per cell. 6 cells times 2.2 volts = 13.2 volts
A depleted battery has a voltage of 1.75 volts per cell. 6 times 1.75 = 10.50 volts. What this means is the operating voltage of a lead acid battery is between 10.50 volts and 13.2 volts. If you allow the battery voltage to fall further than 20% below this operating voltage, sulphation takes place. This is where a layer of lead sulphate forms on the plates blocking replenishment of the voltage.

In order to charge a battery, the supply voltage has to be greater than the operating voltage, but not too great as to cause boiling of the liquid and undue heat.

Note that the “Book” says if the tests do not meet the specifications, replace the TCI. That is of course subject to “common sense” as what your battery voltage was to begin with and if your meter is accurate and the difference between the readings of each leg. My TCI is working sufficiently.

[egsols]

Awesome work Boyat68,

I t would appear that the you have about 92% of battery voltage at the box, Crazcnuk's test showed a similar reading, that is 10.85 volts off a 11.8 volt battery!

I wonder if the specs in the manual are just rounding to infer that the voltage should be that of the battery?

[boyat68]

egsols:

Yes, the voltage at the TCI entrance has to be less than the battery voltage since there is resistance in the connections and wire. The big voltage drop with the key on is the head light as well as the other coils that present resistance to the battery.

[Crazcnuk]

Question is: Is the 92% enough to make the system work correctly?

I assume, too, that my battery is getting weak. It should not be at 11.8v at the START of the testing. I would think it should be somehwere between 12 and 12.8v nominally?

[egsols]

Hey Craz,

I would think that your battery being at 11.8v is starting to get weak.

I can only assume that if it was trickled back up that the TCI readings would increase accordingly.

Based on your readings and Boyat68's it would seem that you are both getting about 92%. If the book calls for a spec of 12v and I reverse the equation I could safely say that a battery outputing 13.2v (fully charged as per Boyat68's post) would give a 12.1v reading at the TCI.

I think one need to be more concerned with an abnormally low reading or inconsistent ones between leads such as Davesxs is experiencing.

[Crazcnuk]

That would seem to make sense. Also, I don't think that the reading, other than as a relative indicator, with the engine off means very much.

The bike has to be running for it to get full volts, at any rate.

[boyat68]

Crazcnuk:

Don't forget that all the TCI does is allow the 12v to saturate the primary side of the coil when the transistor conducts via the pick-up coil induced voltage to the base of the transistor. The original 12v is jumped up to 25000V when the field collapses and is sufficient to step across the gap in the spark plug. When your ballast resistor comes into play, the voltage is reduced but the secondary voltage is enough to shoot the gap of the plug. When your battery voltage falls below a certain level, then the action stops since the secondary voltage is not enough to shoot the gap. I suppose that an enterprising person could put a by pass switch on his ballast resistor and possibly start his machine when the voltage was down below minimums. A trickle charger at Harbor freight only cost about $6 bucks on sale

[TopCatGr58]

Originally posted by boyat68
I suppose that an enterprising person could put a by pass switch on his ballast resistor and possibly start his machine when the voltage was down below minimums.

Hey Boyat68,

That's not needed, the XS11's TCI does just that, it bypasses the circuit going to the Ballast resistor and sends the full 12 volts to the coils during the starting phase for just this reason, to make starting easier. Only after the bike is started and running does the TCI then route the power THRU the ballast resistor circuit to reduce the voltage to spare heating up the coils!
T.C.

[Dennyz]

Get the 'float charger' that Harbor Freight sells. It won't boil your battery out so it can stay on for long periods of time. They run around $13.00, sometime on sale for $8.00, if I remember correctly.

[Dennyz]

When testing the voltage on the TCI (or anywhere on the bike), it is a good idea to have a battery charger (trickle) hooked up. The battery will continue to drain while the key is on. As you check different things, the source voltage continues to drop. This make it very tough to find voltage drops (losses), not to mention make sense of all the different readings. The charger may need to be put on ahead of time to stabilize the battery level.