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Steve, Auto Service Technician
Category: Car
Satisfied Customers: 5494
Experience:  25+ yrs experience as a professional working technician; ASE L1 master technician
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Toyota Avalon: 000 miles..outside temperature..shuts..highway speeds

Resolved Question:

This question is related to Air Conditioning/Heating on my Toyota Avalon, 1998, that has now travelled 180,000 miles. Here's a brief explanation:

When the outside temperature demands that I run the Air Conditioning and/or Heating system in the car, the system starts off and runs very well for a while, and then, suddenly, shuts off. This has happened a few times while moving along at highway speeds, but it seems to happen more when I'm slowed down due to heavy traffic or stopped at a traffic light.
Whenever this problem occurs, basically, the blower motor and all the switches related to AC and Heating fail to operate. Also, the digital display of the outside temperature fails. The system does not come back on until the car has been turned off for a while.
Your help is greatly appreciated.

Jalum Uzele
Submitted: 10 years ago.
Category: Car
Expert:  Steve replied 10 years ago.


The symptoms you describe are likely the result of a failing control module (amplifier) assembly. There is a technical service bulletin from Toyota detailing a revised design amplifier assembly to correct similiar complaints:


December 3, 1999



A production change has been made for the 1998 - 1999 Avalon A/C Amplifier. The internal logic has been corrected to eliminate excessive Air Inlet Servo Motor travel, which may affect the motor and/or the servo-link.


Vehicles with automatic A/C may intermittently experience one or more of the following conditions:
-The ambient temperature display may go blank or display
-Fresh/Recirc indicator light inoperative.
-Mode indicator light inoperative.
-Blower indicator light inoperative.


NOTE: A/C system may restore to normal condition upon cycling the ignition switch.

Applicable Vehicles
All 1998 Model Year Avalon XLS produced before VIN: 4T1BF18B*WU273780


Repair Procedure

1.Remove the Heater Control assembly and replace the A/C amplifier as per the part number.

Remove and replace the Air Inlet Servo Motor.

Inspect the condition of the Servo Link (Damper-plate) for damage as illustrated. Replace if necessary





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