Carrier 69NT40-521 RTS or STS, RRS or SRS, Replacing Sensor STS and SRS, OLD Style Probe Holder

completely immerse bulb) with ice cubes or chipped ice, then filling voids between ice with water and agitating until mixture reaches 0_C (32_F) measured on a laboratory thermometer.

b.Start unit and check air temperature/data readout on the control panel. The reading should be 0_C (32_F); if it is not, continue on to the following step.

c.Turn unit OFF and disconnect power supply.

d.Refer to section 6.27 for removal of the Controller module.

RTS or STS:

Using the plug connector marked “EC” that is connected to the Controller module. Locate the wires marked RTS or STS, depending on which sensor needs to be replaced. Follow that wire to the connector and using the pins of the plug, measure the ohms resistance. Readings are shown in Table 6-1.

RRS or SRS:

Using the plug connector marked “EC” that is connected to the Controller module. Locate the wires marked RRS or SRS, depending on which sensor needs to be replaced. Follow that wire to the connector and using the pins of the plug, measure the ohms resistance. Readings are shown in Table 6-1.

6.23.2 Replacing Sensor (STS and SRS)

To properly position a unit supply sensor, the sensor must be fully inserted into the probe holder. This positioning will give the sensor the optimum amount of exposure to the supply air stream, and will allow the Controller to operate correctly. Insufficient probe insertion into the probe holder will result in poor temperature control due to the lack of air flow over the sensor.

It is also necessary to ensure that the probe tip does not contact the evaporator back panel. The design minimum clearance of 6 mm (1/4 inch) should be maintained (see Figure 6-21).

Cap and Grommet

Assembly

Evaporator

Back Panel

Sensor

Wires

Probe

HolderSupply

Air

Stream

Unit Frame

Supply Sensor

6 mm (1/4 inch)

OLD STYLE PROBE HOLDER

Sensor

Wires Cap and Grommet

Assembly

Evaporator

Back Panel

Probe

Holder

Supply

Air

Stream

Supply Sensor

6 mm (1/4 inch)

NEW STYLE PROBE HOLDER

Figure 6-21. Supply Sensor Positioning

a.Turn unit power OFF and disconnect power supply.

b.Remove and save any cover (if present) over wiring and probe holder.

c.Cut cable 5 cm (2 inches) from shoulder of defective sensor and discard the defective probe only. Save cap and grommet assembly for reuse on the replacement probe. Do not cut the grommet.

d.Cut one wire of existing cable 41 mm (1-5/8 inches) shorter than the other wire.

e.Cut one replacement sensor wire (opposite color) back 41 mm (1-5/8 inches). (See Figure 6-22.)

T-268-07 6-22