1999 430 ML Climate control problem
 

90 k .... A/C outlets alternates from cooling to heating ... A/C switch light remains ON ...while blowing full heat ... reseting the switch starts the process over ( cool to hot ... no consistency for cycling time ... sometimes, cold all day ..sometimes 5 minutes or less. ) A/C switch? ... compressor problem ? .... advice? .

Either a problem with the blend air motor, or the in-car temp sensor.

The in-car temp sensor is par of the Lo/High range switch.

Thanks .... I have personally maintained a 1973 450 SL since 1975 and a 86 300 SDL since 1987 ...I have the CD's and the manuels ... However,, I'm totally clueless regarding the 99 ML ... How would I find or recognize the low/high range switch???
Thanks again .... Ed