A/C - Outside Temperature Indicator Logic Explained

SOURCE:
Honda Service News September 2003

TITLE:
Outside Temperature Indicator Logic Explained

APPLIES TO:
2003-04 Accord EX-Ls and EX V6s and 2003-04 Pilot EXs

SERVICE TIP:
The A/C, solar blocking glass, and heater work so well at keeping the temperature of the passenger's compartment at a comfortable level that it's easy to lose track of just how hot or cold it really is outside. An outside temperature indicator in the gauge assembly gives you a reality check. But keep in mind, the indicator isn't a laboratory-grade thermometer, and it might not give the same temperature as you'd see on signs or buildings with outside temp displays.

The outside air temperature sensor is mounted behind the middle of the front bumper. The gauge control module uses measurements from this sensor to display the outside air temperature.

Because of where the sensor is mounted, it may be affected by heat reflected from the road, the engine, the radiator, or even exhaust from other vehicles. To keep bogus readings to a minimum, the gauge control module uses certain logic. Here's how that logic works:

When you turn the ignition switch to ON (II)

- If the engine coolant temperature is 139�F or lower, the indicator shows the current outside air temperature.

- If the engine coolant temperature is 140�F or higher, the indicator shows the temperature that was stored in memory when you turned the ignition switch to LOCK (0), no matter what the sensor behind the bumper currently measures.

The indicator doesn't refresh until certain criteria are met.

- If the measured outside air temperature is more than the indicated temperature, the indicated temperature rises 1�F every minute once the vehicle reaches and maintains 19 mph for at least 30 seconds. As long as the vehicle speed doesn't drop below that, the indicator refreshes every 60 seconds until the two temperatures match. If the vehicle speed drops below 19 mph, the indicator doesn't start to refresh again until the vehicle speed increases to 19 mph or faster for more than 90 seconds.

- If the measured outside air temperature is less than the indicated temperature, the indicated temperature drops 1�F every 2 seconds until the two temperatures match, no matter what the vehicle speed is.