Olds 98 Automatic Climate Control Temperature Blinks on Startup

The digital temperature indicator on the automatic climate control of my 1992 Olds 98 Regency with 155,000 miles just started blinking when I start it up. It then appears to not function properly. Any idea what's wrong?

This procedure will work on 1992 -1993 models with ATC, and may also work on 1988-1991 models. :dunno:

The diagnostic mode also contains a data list mode and an override mode.

Be careful not to select modes 01 or 02, as these are different modes and may cause you problems, if you don’t know the functions of these modes.

If you suspect you are in the wrong mode, press OFF repeatedly until you exit to normal mode. If the temperature display flashes for 2 minutes when the ignition is turned to RUN, a trouble code is set.

1. Turn ignition to RUN. Press OFF and WARM (temperature up) buttons simultaneously.

2. Watch the segment test, then the trouble codes will be displayed.

3. Code Key:

00 - No codes

10 or 110 - Ambient Temp Sensor circuit open or shorted.

13 or 113 - In-Vehicle Temp Sensor circuit open or shorted.

15 or 115 - LH Solar Sensor circuit open or shorted.

35 or 135 - Data Line failure - HVAC Control Assembly

38 or 138 - Data Line failure - PCM

40 or 140 - Driver Air Mix Motor circuit open or shorted, or not calibrated

48 or 148 - Long Term Freon Loss

52 or 152 - Keep Alive Memory lost; sets with battery disconnected

66 or 166 - Low Freon

A number (1) prefix, indicates a history trouble code.

4. Press OFF twice, once codes are displayed to end diagnostic mode, OR to clear trouble codes, press FAN DOWN three times (make sure 03 is displayed).

Once 03 is displayed, press FAN UP to clear trouble codes. Then repeatedly press OFF to end diagnostic mode.

I got a trouble code 66, low freon. Seems like an unusual problem for the ATC to not work, but at least it's reasonably cheap and simple to fix. I'm out of town until next weekend but plan to take the car in for service next Saturday. Will let you know if the freon solves the problem.
Thanks.
Jim

Too cold to add freon! I'll let you know when it warms up enough.
Jim

Do you still have the original R-12 in the system? If so, that stuff has become outrageously expensive since the production was seized during 1996! It might be time to flush the system, add POA oil & convert to 134A! Get a price comparison on your options before you commit to service! BTW, get quotes from several reputable shops! It will be getting warm in Houston before you know it!