Rheostat

Fig. 11 Checking ATC rheostat:

When there is an open circuit in the rheostat, the system will operate at maximum cooling; and when there is a short circuit in the rheostat, the system will operate at maximum heating. To check rheostat, proceed as follows:
1. Remove safety pad, heater control assembly and related components, then connect a suitable ohmmeter between terminals 3 and 4 on the A/C control switch connector No. 9, Fig. 11.
2. Place rheostat lever at mid-position, then check ohmmeter indication.
3. Resistance should be 1500 ± 225 ohms.
4. If resistance is not as specified, replace rheostat.