The Thermo King Alarm 89 indicates the status of the Electronic Throttle Valve (ETV) circuit and is presented in the following table:
Alarm Code 89:
- Color Indicator: Green = OK
- Description: Check the Electronic Throttle Valve (ETV) circuit.
- Operator Action: If the unit shuts down, repair it immediately. Otherwise, report the alarm at the end of the day.
Key Information about Thermo King Alarm 89 and ETV:
The ETV is a variable-position valve operated by a stepper motor. Key details include:
- Location: The ETV is positioned in the suction line between the evaporator and the compressor.
- Pressure Transducers: Discharge and suction pressure transducers provide pressure information to the microprocessor control system.
- Control: The microprocessor directly controls the Electronic Throttle Valve.
- Replacement: The ETV replaces both the throttle valve and modulation valve used in other units.
- Circuit Advantages: The ETV circuit extends maintenance intervals and reduces fuel costs, improving temperature control in Thermo King products.
Parts of the Thermo King ETV:
The main components of the Thermo King ETV include:
- Output
- Stepper Motor
- Valve Body
- Input
The ETV system enhances cooling system control by providing optimal power usage under variable conditions.
Control of ETV Suction Pressure:
The algorithm for controlling suction pressure is crucial for maximizing capacity. The ETV, a variable-position valve, operates with two internal coils. Key points:
- The ETV position can be monitored using the METERS key.
- A position of 0 indicates a fully closed valve, while 800 indicates a fully open valve.
- The microprocessor tests the ETV valve each time the unit starts if required.
- Alarm Code 89 indicates that the refrigeration system pressures did not respond as expected during the test.
What to Do with Thermo King Alarm 89:
When faced with Alarm 89, follow these steps:
- Locate the ETV circuit in the upper half of the compressor.
- Check for loose plugs.
- Clean ground cables, a common cause of system malfunctions.
- Verify pressure sensor readings against actual system values.
- Use the METERS key to monitor ETV operation during the ETV test.
- The ETV test should start with the valve completely closed (position 0) and increase as the valve opens.
- Suction pressure should decrease when the valve is fully closed and begin to rise as the valve opens.
Additional Notes on Thermo King Alarm 89:
- The microprocessor disregards test results if the cargo box temperature or ambient temperature is below 10F (-12C).
- The ETV valve test can also be performed using the Service Test Mode.
- Use the METERS key to review ETV functionality during the ETV test.
