This solenoid can be used for one of two options; A/C or Fast Idle. The Fast Idle/ A/C Solenoid does not require an additional valve. The fast idle option consists of extra circuitry added to the ECU, a control wire, a modified relay and an air bypass solenoid. When the coolant or CHT is below a certain temperature, which is now user programmable, the ECU commands the solenoid to open and bypass additional air past the throttle plate to increase idle speed. As the engine warms up near normal operating temperature, the ECU closes the solenoid to restore the normal hot idle rpm setting. This option is recommended in cooler climates where warmup time is extended and oil viscosity reduces the cold idle rpm to unacceptably low levels. Scraping the frost and snow off of your car is certainly easier with this option. On most engines, the solenoid allows the engine to achieve between 800 and 1500 rpm during the warmup cycle. Installation requires running 5/16 vacuum hose from the air filter to the solenoid and from the solenoid to the intake manifold. The control system is either on or off.
The A/C option consists of an air bypass solenoid of the same type supplied for the fast idle option. This solenoid is hooked up directly to the air conditioning clutch circuit. When the a/c clutches in, the solenoid opens to increase engine idle speed by bypassing air past the throttle plate. This prevents sagging rpm with a/c operation. 5/16 vacuum hose connections to the air filter and intake manifold are required. This option is not controlled by the ECU.
NOTE: This part is to be used with our Pro Fuel Injection Systems only not for stock Toyota ECU's.
Contact our Tech Support Line for further information at 928-855-6341.
Check out LCEngineering.com for New Products, Tech Articles, Specials & Monthly Newsletters!
To open a printable PDF version of this instruction
Optional Fast Idle:
The fast idle option consists of a solenoid valve which connects to the intake manifold via 5/16 vacuum hose and a relay controlled by the EM-5 via the engine temperature sensor. When the engine temperature reaches the preset point, set in the window, FAST IDLE SWITCH, the relay closes the solenoid to allow normal idle speed. Below this temperature, the solenoid is open bypassing additional air around the throttle plate. The point of solenoid closing (off) is adjusted under the FAST IDLE SWITCH parameter by using the +1 and -1 buttons. Note that the -1 button raises the temperature set point and the +1 button lowers it. The cut off point would usually be set between 100 and 140F on most engines.
Relay connections are as follows:
*Note: Optional diode is not required if Pin 13 A/C sense wire is connected to the A/C clutch positive wire. Only
use diode on “D” (fuel only) type SDS systems.
Air Conditioning Solenoid
The a/c solenoid is used to speed up the idle when the a/c compressor is running. This valve is the same valve
that is used for fast idle operation. If you have the fast idle option installed, then there will be no need for a
second solenoid valve. If you don’t have the fast idle option then you will need the valve, and it’s terminal must
connect to the a/c clutch (+) wire, and the solenoid body must be grounded. Hose connections are the same as
for the fast idle relay option above.
For EM-5D (fuel only)
You can install a diode connected between the fast idle valve and the a/c clutch (+) connection. See the fast idle
diagram. The diode allows current to flow from the a/c clutch over to the valve. If the fast idle circuit is turned on,
then the diode will block any current from the fast idle circuit from going to the a/c clutch.
For EM-5E and EM-5F if you have fast idle option and/or radiator fan relay option:
You can use the PIN 13 green wire input for A/C sensing, and this input will activate the radiator fan relay and
can also activate the fast idle relay when the A/C is operating. See the E or F supplement manuals for more
This option is not suitable for TP load sensing systems(no MAP sensor), because of the inability to compensate
for the extra load on the engine.