Specific Switch Function
FIGURE 3 - TORQUE CONVERTER SIGNAL SWITCH:
1. "Torque Converter Signal" Switch (P/N 8642473)
This is a single terminal normally open switch. The function of this switch is to make an electrical ground when the converter clutch is applied and break the ground when the clutch is released. For all 1982 and 1983 non-ECM vehicles with TCC signal, this switch is wired in series with the 3rd clutch switch (see Figure 3).
2. 3rd Clutch Switch (P/N 8643710)
This is a two-terminal normally open switch. It is currently wired in series with the TCC signal switch and allows current to flow to the TCC signal switch only when the transmission is in third gear, although the high altitude option is an exception. The combined function of the 3rd clutch switch and the TCC switch is as follows:
^ Twelve (12) volts D.C. 0.20 amp electric current is sent across the EGR solenoid (60 ohms). With either switch open, the current cannot flow. This signals the EGR solenoid that the transmission is not in third gear and that the converter clutch is released. When the transmission is in third gear and the converter clutch is applied, the electrical current from the EGR solenoid flows through the 3rd clutch switch and grounds through the TCC signal switch. This signals the EGR solenoid to release emission control (see Figure 3).
FIGURE 4:
3. 4-3 Downshift Switch (P/N 8642346)
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).
The following procedure may be used in diagnosing the oil pressure switches:
OIL PRESSURE SWITCH CHECKING PROCEDURE
TOOLS REQUIRED: AIR LINE ADJUSTABLE TO 60 PSI BATTERY POWERED TEST LIGHT
Switch Type Part No. Step: Action Result
Single Terminal 8642473 1: Connect test light leads 1: Light off
Normally open Silver to the terminal and switch
Housing body; air pressure < 10 psi
2: Apply air pressure to the 2: Light on
switch; air pressure > 30 psi
Single Terminal 8634475 1: Connect test light leads 1: Light on
Normally closed 8642569 to the terminal and switch
Black body; air pressure < 30 psi
Housing 2: Apply air pressure to the 2: Light off
switch; air pressure > 55 psi
Double Terminal 8643710 1: Connect the test light 1: Light off
Normally open Silver leads to the switch
Housing terminals; air pressure < 10 psi
2: Apply air pressure to the 2: Light on
switch; air pressure > 30 psi
Double Terminal 8642346 1: Connect the test light 1: Light on
Normally closed Black leads to the switch
Housing terminals; air pressure < 7 psi
2: Apply air; pressure to the 2: Light off
switch; air pressure > 14 psi
Provided below is a chart that shows specific switches required for the various types of transmission usages. Refer to your service manual for wiring diagrams of each vehicle type if needed.
VEHICLE TYPE AND SWITCHES REQUIRED
Type TCC SIG SW 3RD CL SW 4-3 DS SW 4TH CL SW
1 8642473 8643710 8642346 8643710
2 Plug Plug 8642346 8643710
3 Plug Plug 8642346 Plug
4 Plug Plug 8642346 8634475 (8642569)
5 8642473 8643710 8642346 8642473
6 Plug Plug Plug Plug
7 8642473 Plug Plug 8643710
8 Plug Plug Plug 8643710
9 Plug Plug Plug 8634475 (8642569)
10 Plug Plug 8642346 8642473