S15/T15 Jimmy 2WD L4-119 1.9L VIN A 2-BBL (1983)
This is a normally closed two terminal switch. The 4-3 downshift switch is sometimes referred to as a pulse switch and performs the function of
releasing the converter clutch when a 4-3 downshift is made (see Figure 4). The 4-3 downshift switch is activated by exhaust oil from the 4th clutch.
After the 4th clutch oil has exhausted, the switch closes and allows the converter clutch to reapply. This momentary release (pulse) of the converter
clutch allows the transmission to make a 4-3 downshift without any objectional shift feel.
FIGURE 5 - ELECTRICAL SCHEMATIC 4TH CLUTCH SWITCH
4.
4th Clutch Switch
One of three different switches may be installed in this location depending on vehicle usage.
A.
4th Clutch Switch (P/N 8643710)
This switch is a normally open two terminal switch. The function of this switch is to keep the converter clutch applied in 4th gear regardless of
engine vacuum (see Figure 5).
FIGURE 6 - EXAMPLE OF 4TH DISCREET SWITCH ELECTRICAL SCHEMATIC
B.
4th Discrete Switch (P/N 8634475 or P/N 8642569)
These are normally closed single terminal switches. They are used in vehicles with ECM's. The purpose of either switch is to signal the ECM when
the vehicle is in 4th gear (see Figure 6).
FIGURE 7 - EXAMPLE OF 4TH CLUTCH SWITCH ELECTRICAL SCHEMATIC
C.
Fourth Clutch Switch (P/N 8642473)
This is a normally open single terminal switch. The function of this switch is to keep the converter clutch applied in fourth gear regardless of
any other controls (see Figure 7).
