Outside Temperature Sensor - Memory Feature

FILE IN SECTION: 1 - HVAC

BULLETIN NO.: 53-12-10

DATE: July, 1995

SUBJECT:
Section 1C - Additional Information for Outside Temperature Sensor Memory Feature

MODELS:
1995 Buick LeSabre, Park Avenue
1995 Oldsmobile Eighty Eight, Ninety Eight
1995 Pontiac Bonneville

The following information concerning the outside temperature sensor should be added to Section 10-8, "Ambient Temperature Sensor", in the Service Manual.

During periods of city traffic and idle conditions, engine heat can surround the area of the outside temperature sensor and cause temperature readings that are higher than the actual outside air temperature. The programmer is designed to minimize unwanted temperature variations.

A temperature memory feature is used in the HVAC programmer outside temperature programming to help provide greater accuracy under engine restart conditions. It engine coolant temperature is less than 10°C (50°F) above the outside temperature sensor reading, the actual sensed outside temperature is displayed. However, it engine coolant is greater than 10°C (50°F) above the sensor reading, memorized outside temperature is displayed. This is the displayed temperature sensed when the engine was previously operating.

At vehicle speeds greater than 32km (20 mph), the outside temperature display may be allowed to increase, but only after a built-in 80 second time delay which allows for outside air to cool the sensor. The 80 second time delay starts when vehicle speed reaches or maintains at least 32km (20 mph). It the sensor reading is ever less than the displayed value or if the vehicle speed is 72km (45 mph) or greater, there is no delay and outside temperature changes are displayed as rapidly as possible. If the sensor fails, a default value of 10°C (50°F) will be used by the programmer.