Hello, my 1997 LS 400 developed an intermittent problem with the climate control panel. I purchased the car a month ago and the problem suddenly came up this week.

THE PROBLEM -
Usually when I start the car, some of the climate control panel buttons and functions do not work. However, after 1-2 minutes of driving (or idling), everything works and it keeps working fine. Until.... I shut the car off. Then usually the problem re-appears, and then again after 1-2 minutes it disappears.

THE BUTTONS and FUNCTIONS THAT INTERMITTENTLY STOP WORKING -
- Temperature "down" on the driver side only. (On passenger side, it works, but only in DUAL mode)
- Rear defrost does not come on
- Mode button does not work
- Front defrost works, but the fan control does not work with front defrost on
- Other things don't work either, but I would have to experiment more to know.

I ran the diagnostics by pressing Auto+Recirc and starting the engine, and the only two codes are 21 (the solar sensor, which is not a concern) and 24 (which I do not see on any lists of diagnostic codes). For BOTH codes there is a beep which I understand means the problem no longer is happening.

After being a problem for 1-2 minutes after starting the engine, suddenly it will go away and everything works again.

One thing that might be a coincidence is that earlier I did remove the center console cover to repair the front and rear cigarette lighter/charging port, and this involved un-plugging some connections that might have been on the same harness as the climate control and stereo. Maybe I loosened a connection up behind the climate control panel?

Has anyone seen this problem and fixed it? Also, does anyone know what error code 24 means?

Thanks!

 

The code 24 is for the 2nd solar sensor. Both 21 and 24 appear when you diagnose the unit at where the sun can't be seen. So don't worry as long as you are not checking your car under the sun.

Regarding the problem which only happens for 1-2 minutes after the car is started up, it is a typical symptom of a failing DC-DC converter in the climate control unit. I'd check the DC voltage and the ripple voltage level using an oscilloscope for the confirmation. Another simple method is to use a hair dryer. Warm up the climate control unit until the inside of it reaches 100 degrees F+ and start the engine. If the unit works fine right after the starting up, electrolytic capacitors used at the DC-DC converter circuit should be replaced.