QuestionHi - I have a 98 Grand Prix GT with the 3.8L engine and most of the goodies, including a HUD, dual climate control, and read outs. The a/c works well when it gets going! The problem is a sometime improper external temperature reading on the climate control. A little hard to explain. An example might be sufficient. Parked overnight and in the morning the ext temp reading is correct (if I believe the radio). The overnight temperature is, say 18 C. Start up the car and everything is rosy!; however, it is now mid afternoon and the ext temp is 30 C. The ext temp reading is still 18 C. and the climate control acts appropriately, i.e. provides some cooling. NOW..., to get the ext temp reading to correct itself and decide it is really 30 C. outside and provide appropriate cooling (which it does); as far as I can determine, the car has to travel at least 2 km without stopping! On a good run (2 km or more) I can amaze my friends by telling them to watch the ext temp readout and can predict, within 0.2 km (over 2 km) that the temp reading will increase to the actual outside temperature. If the car stops within the 2 km, the process must begin again - I can drive, say, 25 km in the city hitting each stop light, and the ext temp reading remains the same. Please note, the ext read out reacts very nicely to a decrease in temperature, but not an increase. I don't know whether there is a connection between the climate control and initial speed, or there is a 'temperature delay switch in the control module, or the brakes or timed air flow, or the speedometer, or all of them, or none of them, or some wire or switch must be 'heated up' over a certain continuous distance, or,...I just don't know'!. Is there something to clean, remove, beat, change, or swear at that might get me some relief while sweating in rush hour traffic?
This is an annoyance, but not worth buying a new climate control, and I really don't want exploratory surgery done on the climate control gizmo.
(I have changed the ambient outside air temperature sensor and there is no difference in performance)
AnswerThere is a delay in the outside temp reading. It should read the temp that it was when the car was shut off last and then should readjust itself within a few minutes after the next startup. This is for situations like, its 80*f outside and you park the car in the shade for a couple hours. When you start it back up, the real temp is still 80 but the temp in the shade is only 70, the AC would not work correctly, so the delay still reads 80.
There has to be airflow across the outside temp sensor to get good readings. From the problem that you described, and seeing that you have replaced the sensor, I would say that the problem is in the programmer, not the control head.
