In 1975, Toyota introduced its transistorized ignition system. This system works very much like the conventional system previously described. Regular breaker points are used, but instead of switching primary current to the coil off-and-on, they are used to trigger a switching transistor. The transistor, in turn, switches the coil primary current on and off.
Since only a very small amount of current is needed to operate the transistor, the points will not become burned or pitted, as they would if they had full primary current passing through them. This also allows the primary current to be higher than usual because the use of a higher current would normally cause the points to fail much more rapidly.
As already stated, the condenser is used to absorb any extra high voltage passing through the points. Since, in the transistorized system, there is no high current, no condenser is needed or used.
As a result of the lower stress placed on them, the points only have to be replaced every 24,000 miles (38,000 km) instead of the usual 12,000 miles (19,200 km).
The Toyota transistorized ignition system may be quickly identified by the lack of a condenser on the outside of the distributor and by the addition of a control box, which is connected between the distributor and the primary side of the coil. This system was available on all 1975-77 models.
Basically, the transistorized ignition is serviced just like its conventional counterpart. The points must be checked, adjusted, and replaced in the same manner. Point gap and dwell must be checked and set. The points should also be kept clean and should be replaced at 24,000 mile (38,000 km) intervals. Of course, since there is no condenser, it does not have to be replaced when the points are.
However, there are several precautions to observe when servicing the transistorized ignition system:
- Use only pure alcohol to clean the points. Shop solvent or an oily rag will leave a film on the points which will not allow the low current to pass.
- Hook up a tachometer, dwell meter, or a combination dwell/tachometer to the negative (-) side of the coil; NOT to the distributor or the positive (+) side. Damage to the switching transistor will result if the meter is connected in the usual manner.
- See the previous section for the remaining service procedures which are identical to those for the conventional ignition system.