On a York Predator rooftop, the freezestat is a suction line switch that protects the evaporator from freezing. York form 127408-YIM-B-0606 (Predator DM090–DM150, 50 Hz) gives it as opening at 26 ± 5°F and resetting at 38 ± 5°F. When it opens during cooling, the unit control board shuts off that compressor; three openings within two hours lock the compressor out and flash a code. The replacement listed for 60 Hz DH090 models is S1-02541330000, titled 26 Open / 38 Close; the DH technical guide (form 246646-YTG-C-0606) confirms DH units have suction line freezestats with the same three-trips-in-two-hours lockout.
What does the freezestat do?
Form 127408-YIM-B-0606 lists three monitored safety inputs for each cooling system:
- A suction line freezestat, to protect against low evaporator temperatures.
- A high-pressure switch, to protect against excessive discharge pressure.
- A low-pressure switch, to protect against loss of refrigerant charge.
The manual says the refrigeration systems are independently monitored and controlled, and a freezestat trip acts on the associated compressor. The DH technical guide (246646-YTG-C-0606) says suction line freezestats are supplied on all DH units to protect against loss of charge and coil frosting.
What happens when the freezestat opens?
| Step | What the UCB does (127408-YIM-B-0606) |
|---|---|
| Freezestat opens during cooling | De-energizes the associated compressor and starts the anti-short cycle delay (ASCD) |
| Other compressor idle | Condenser fans stop as well |
| End of the ASCD | If cooling is still called for, the compressor restarts |
| Third opening within two hours | Locks out the associated compressor and flashes a code; condenser fans turn off if the other compressor is inactive |
The manual says all system errors override the compressor minimum run times.
Which flash code means a freezestat lockout?
The UCB flashes its codes on the red LED at the lower left of the board. Table 52 of the manual lists:
| UCB flash code | Description |
|---|---|
| Heartbeat (1 second on/off) | Normal operation, not an error |
| 2 flashes | Control waiting ASCD |
| 3 / 4 flashes | HPS1 / HPS2 compressor lockout |
| 5 / 6 flashes | LPS1 / LPS2 compressor lockout |
| 7 flashes | FS1 compressor lockout (freezestat, system 1) |
| 8 flashes | FS2 compressor lockout (freezestat, system 2) |
| 10 flashes | Compressors locked out on low outdoor air temperature |
Pressing and releasing the LAST ERROR button cycles through the last five alarms, most recent first, about 2 seconds apart. That is useful when the unit has already restarted by the time you arrive.
How do you reset a freezestat lockout?
The manual says to raise the thermostat setting above the room temperature to remove the cooling call. That clears pressure switch and freezestat flash codes. For troubleshooting, pressing and releasing the TEST/RESET button once zeroes the compressor ASCDs for one cycle.
Our practical advice, not from the manual: a freezestat that trips three times in two hours is usually telling the truth about the coil. Before you reset it again, check the things that starve an evaporator of heat or refrigerant: dirty filters, a slipping blower belt or failed blower, a dirty evaporator coil, low charge or a restriction.
Does the freezestat lock out in low ambient cooling?
No. Per form 127408-YIM-B-0606, a temperature switch set at 45°F starts low ambient mode when it closes on a cooling call. Compressors then cycle 10 minutes on and 5 minutes off, with the indoor blower running throughout the cycle. In this mode the compressors are not locked out for freezestat trips. A trip still shuts the compressor off, and it restarts at the end of the ASCD if cooling is still called and the freezestat has closed.
How is this different on newer J**ZJ units?
Johnson Controls J**ZJ rooftops with Smart Equipment controls (form 5167530-JIM-H-0218) use an evaporator low limit sensor (EC1, EC2) for the suction line temperature safety instead of a freezestat switch. It trips below 26°F by default, with the same three-in-two-hours lockout rule. If your unit's model starts with J, see our J10ZJ page rather than the Predator pages.
Parts involved
| Component | Role | Where to find it |
|---|---|---|
| Freezestat | Suction line low-temperature switch. Listed for DH090, DH120, DH102, DH078, DF090 and DM090 models. Its title rating (26 open / 38 close) matches the manual's nominal values. | York S1-02541330000 Freezestat, 26 Open / 38 Close, with Harness, P11, FS1-2 | OEM Source 1 Part |
| Compressor contactor | Drops out when the UCB de-energizes a compressor. Listed for DH090, DH120, DH102, DH078 and DF090. | York S1-02424101700 Contactor 2PNO, 20A, 24V | OEM Source 1 Part |
| Indoor blower motor | Low airflow across the coil is a common reason the coil gets cold. Listed for DH090 and DM090. | York S1-02419623716 Blower Motor, 2 HP, 1725 RPM, 208-230/460V 3-Ph, Reversible | OEM Source 1 Part |
| Air filter | Listed for DH090 and DH120. | York S1-02625535000 Air Filter, Mist, 23-1/8 x 24-5/8 x 1 | OEM Source 1 Part |
Which York units this applies to
- York DH090 parts — 7.5-ton Predator, primary page for the freezestat.
- York DH120 parts — 10-ton Predator.
- York DH102 parts — 8.5-ton Predator.
- York DM090 parts — 7.5-ton Predator, the model family the cited manual covers.
- York DF090 parts — 7.5-ton Predator.
- York J10ZJ parts — newer J**ZJ unit with an evaporator low limit sensor instead.
Scope: Freezestat settings, flash codes, low ambient rules and reset steps are from York form 127408-YIM-B-0606, Installation Manual for Predator DM090, DM120 and DM150 (50 Hz) only. We could not obtain the 60 Hz DH installation manual. For DH078–DH150, the technical guide (246646-YTG-C-0606) confirms only the suction line freezestat and the three-trips-in-two-hours lockout. The freezestat listed for DH090 carries a 26/38 rating in its title, but confirm settings and flash codes against your unit's manual. The J**ZJ comparison is from form 5167530-JIM-H-0218.
Before you order
Take the model and serial number from the nameplate and check which system (FS1 or FS2) tripped. Contact us at help@totalhvacparts.com or 610-487-7999 with the model, serial and part number to confirm fit.
Frequently Asked Questions
At what temperature does a York Predator freezestat open?
Form 127408-YIM-B-0606 (DM090–DM150, 50 Hz) gives 26 ± 5°F open and 38 ± 5°F reset. It is mounted on the suction line.
What does 7 flashes mean on a York Predator unit control board?
In Table 52 of form 127408-YIM-B-0606 (DM090–DM150), seven flashes is an FS1 compressor lockout: the system 1 freezestat opened three times within two hours. Eight flashes is the same for system 2.
How do I clear a freezestat lockout on a York Predator?
Raise the thermostat setting above room temperature to remove the cooling call, which clears the code. Find the cause of the cold coil before restarting.
Why does my York Predator not lock out on freezestat in cold weather?
Per form 127408-YIM-B-0606 (DM090–DM150), in low ambient mode, started by a 45°F temperature switch, compressors are not locked out for freezestat trips. A trip still stops the compressor until the freezestat closes and the ASCD ends.
Sources
- York form 127408-YIM-B-0606, Installation Manual, Predator DM090, DM120, DM150, 50 Hz (cooling operation errors, freezestat, low ambient cooling and safety controls p.41; reset p.42; Table 52 UCB flash codes and LAST ERROR / TEST/RESET p.50)
- York form 246646-YTG-C-0606, Technical Guide, Predator DH078, 090, 102, 120 and 150 (suction line freezestats, lockout rule)
- Johnson Controls/York form 5167530-JIM-H-0218, Installation Manual, J**ZJ Series with Smart Equipment (evaporator low limit, p.54)
- 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.