On York/Johnson Controls J**ZJ rooftops with the Smart Equipment (Simplicity SE) control, the supply, return and outdoor air sensors are all 10KΩ at 77°F, Type III negative temperature coefficient (NTC) thermistors, per York form 5167530-JIM-H-0218. To test one, check its resistance against that rating with the sensor unplugged. Then check the board input: the manual gives 3.625 VDC across each sensor input with an open circuit, so in our reading about 3.6 VDC with the sensor connected suggests an open sensor or broken lead.
Which temperature sensors does the Smart Equipment board use?
Table 30 ("Smart Equipment UCB Details") in form 5167530-JIM-H-0218 lists these thermistor inputs. All of them are described as 10KΩ @ 77°F, Type III negative temperature coefficient thermistors.
| Terminal | Sensor | Required? | What the board uses it for |
|---|---|---|---|
| SAT+ | Supply air temperature | Input required for operation | Supply air temperature input |
| RAT+ | Return air temperature | Input required for operation | Return air enthalpy; substitutes for space temperature if no other input is present |
| OAT+ | Outdoor air temperature | Required, but may be a communicated value | Heat/cool cutouts, low ambient cooling, free cooling changeover, outdoor enthalpy, economizer loading, heat pump demand defrost |
| EC1+ / EC2+ | Evaporator coil (suction line) temperature, circuit 1 / 2 | EC1 required; EC2 on 2-compressor units | Suction line temperature safety |
| CC1+ / CC2+ | Condenser coil temperature | Heat pumps only (not required for A/C units) | Heat pump demand defrost |
| ST | Space temperature sensor input | — | Space temperature (RAT substitutes if no other input is present) |
Because the evaporator coil sensors are the same type, a bad EC sensor can show up as a cooling problem. The manual locks out a compressor after the EC sensor reads below 26°F three times within two hours.
How do you check the sensor input voltage?
For each thermistor input in Table 30 (SAT, RAT, OAT, EC1/EC2, CC1/CC2), the manual gives a 3.625 VDC reading across the + and – terminals with an open circuit. It also gives these readings:
| Measure | Value given in 5167530-JIM-H-0218 | What it tells you |
|---|---|---|
| SAT+ to SAT– | 3.625 VDC with open circuit | Our reading: about 3.6 VDC with the sensor connected suggests the board sees an open sensor or lead |
| ST to COM | 3.625 VDC with open circuit | Same check for a wall space sensor |
| SSO to COM (space sensor offset) | 10KΩ / 2.5 VDC = 0°F offset; 0Ω / 0 VDC = maximum above; 20KΩ / 3.4 VDC = maximum below | Checks the setpoint-adjust potentiometer on a space sensor |
Use a meter on DC volts with the board powered, and keep clear of line voltage terminals in the control box.
How do you check the sensor itself?
- Turn off power and follow lockout/tagout.
- Unplug the sensor from the board so the board does not load the reading.
- Measure resistance across the two sensor leads.
- Measure the actual air temperature at the sensor with a reference thermometer.
- Compare. The manual rates these sensors at 10KΩ at 77°F. Because they are negative temperature coefficient types, resistance goes down as temperature goes up and up as temperature goes down.
An open reading (no continuity) or a dead short means the sensor or its lead is bad. The York manual we read does not print a full resistance-versus-temperature chart, so for readings far from 77°F use a published Type III 10K thermistor chart, or compare against a known-good sensor at the same temperature.
Our practical advice, not from the manual: before you condemn a sensor, check the plug and the lead along its whole run. Sensor leads on rooftops get pinched by panels and chewed at grommets. Then compare the reading with a thermometer at the same spot.
Where does a dirty filter or air proving alarm fit in?
Not every "sensor" alarm is a thermistor. The same table lists the dirty filter switch (DFS), which raises a notification alarm when closed for more than 15 seconds during blower operation, and the optional air proving switch (APS). The APS must close within 30 seconds of blower start and not open for more than 10 seconds, or the board raises an "APS open" alarm. These are 24 VAC switch inputs, so test them for voltage in and out, not resistance.
Parts involved
| Component | Role | Where to find it |
|---|---|---|
| Air temperature sensor, 6 in | Outside, return or supply air sensor. Listed for J07ZJ and J10ZJ models. | York S1-6043480 Temperature Sensor, Outside/Return/Supply, Air, 6 in | OEM Source 1 Part |
| Return/supply/outdoor sensor | Listed for J07ZJ, J10ZJ, J15ZF and J15ZJ models. | York S1-33103655000 Temperature Sensor, Return, Supply, Outdoor | OEM Source 1 Part |
| Temperature sensor, female, no clip | Listed for J07ZJ and J10ZJ models. | York S1-02550564000 Temperature Sensor, -40 to 110C, Female, without Clip | OEM Source 1 Part |
| Temperature sensor, 10 ft, female, with clip | Clip-on style. Listed for J07ZJ and J10ZJ models. | York S1-02549697000 Temperature Sensor, 10 ft Lead, Female, with Clip | OEM Source 1 Part |
| Temperature sensor, 10 ft, male, with clip | Listed for ZF180, J15ZF, J15ZJ and J20ZJ models. | York S1-02549696000 Temperature Sensor, 10 ft Lead, Male, with Clip | OEM Source 1 Part |
| Temperature sensor, 72 in, male, no clip | Listed for ZQG06 models. | York S1-6043485 Temperature Sensor, -40 to 105C, Male, without Clip, 72 in. | OEM Source 1 Part |
The connector gender and clip style matter. Match the old sensor's plug and mounting before ordering.
Which York units this applies to
- York J10ZJ parts — 10-ton J**ZJ rooftop covered by form 5167530-JIM-H-0218.
- York J07ZJ parts — 7.5-ton J**ZJ, same manual.
- York J15ZJ parts — 15-ton ZJ; check its own manual.
- York ZF180 parts — 15-ton ZF; uses its own manual, so check its control and sensor type there.
- York ZQG06 parts — 5-ton gas/electric; sensor 6043485 is listed here.
For the board's alarm LED and lockout rules, see our article on the York Simplicity SE board (J**ZJ fault LED, alarms and lockouts).
Scope: Sensor type, terminal functions and voltage readings are from York/Johnson Controls form 5167530-JIM-H-0218 (J**ZJ Series with Smart Equipment, J06 to J12ZJ, 6-1/2 to 12-1/2 ton, 60 Hz), Table 30. The ZJ150 manual (1183875-YIM-A-1014, Table 29) describes its supply air and space temperature inputs the same way. Older Simplicity, Simplicity Lite and non-SE controls may use different sensors and readings.
Before you order
Note the nameplate model and serial number, which sensor you are replacing (supply, return, outdoor or coil), and the part number or plug style on the old sensor. Contact us at help@totalhvacparts.com or 610-487-7999 to confirm fit.
Frequently Asked Questions
What resistance should a York rooftop supply air sensor read?
For J**ZJ Smart Equipment units, York form 5167530-JIM-H-0218 rates the SAT, RAT and OAT sensors at 10KΩ at 77°F, Type III NTC. Resistance falls as temperature rises.
What voltage should I see at the York SAT terminals?
Form 5167530-JIM-H-0218 gives 3.625 VDC from SAT+ to SAT– with an open circuit. A reading near that with the sensor connected suggests an open sensor or broken lead.
Will a York Smart Equipment rooftop run without the return air sensor?
The manual lists the return air temperature input as required for operation, along with supply air and evaporator coil 1. The outdoor air input is required but may be a communicated value.
Are York supply, return and outdoor air sensors the same part?
On the Smart Equipment board they are the same sensor type (10KΩ at 77°F, Type III NTC), and some listings are titled for outside, return or supply use. Lead length, plug gender and clip style still vary, so match the old part.
Sources
- Johnson Controls/York form 5167530-JIM-H-0218, Installation Manual, J**ZJ Series with Smart Equipment, 6-1/2 to 12-1/2 ton, 60 Hz (Table 30 Smart Equipment UCB Details, pp.65–66; cooling operation errors p.54)
- York form 1183875-YIM-A-1014, Installation Manual, ZJ150 (Table 29 Simplicity SE UCB Details: SAT and ST inputs)
- Live product titles for the parts listed above, as shown on each product page
Rooftop units involve line voltage, refrigerant under pressure and rotating parts. Service should be performed only by qualified personnel, following the manual for your unit and your facility's lockout/tagout procedures.