POWER TRAIN
-
Automatic Transaxle
2-59
;.
c
I?
f
D
2
r
Fluid venting
from UD clutch
(through
Ul
orifice
and thermal valve)
Cold-open
from UD clutch
Hot-closed
No pressure
switch off
With pressure
switch on
Thermal Valve
The thermal valve is a bi-metallic shutter valve that helps control
the venting rate of oil pressure in the underdrive clutch passage
during release of the clutch. When the oil temperature is approxi-
mately 20 degrees Fahrenheit or less, the valve will be fully
open to assist in venting oil past the
Ul
orifice. At temperatures
above 20 degrees, the valve starts to close and becomes fully
closed at approximately 140 degrees, The thermal valve is
located in the transfer plate of the valve body.
Pressure Switches
The pressure switches in the solenoid assembly supply informa-
tion to the TCM. When pressure is applied to a hydraulic circuit
where there is a pressure switch, the switch is forced to the
“on” or closed position. The switches do not tell the TCM how
much pressure there is in a circuit, but rather that pressure
does exist. Basically, the switches confirm to the TCM that
the intended solenoid action did occur. They can also be used
to determine a hydraulic problem.
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