Bryant

LPS

Lockout

Low pressure / freeze

Suction dropped out — charge, indoor airflow, or TXV.

2 plates — walk the one on the cabinet

First check

1 Airflow and freeze before you add gas

On Bryant 187B low pressure / freeze is indoor airflow or a starved coil until proven otherwise. Filter, blower, dirty A-coil, closed supplies. In heat mode, a iced outdoor coil is the same family. Indoor filter, blower, coil freeze. Do not add gas on a frozen coil.

Expect: Indoor air moving. Coil not iced. OD coil clear in heat.

The rest of the walkthrough is Diagnose.

On the plates

Indoor filter, blower, coil freeze. Do not add gas on a frozen coil.
TXV / restriction. Weigh-out if the history is a leak.
Low ambient and wind can nuisance-trip LPS on a light load — still prove charge.
Charge / leak. Filters and indoor coil first — a dirty rooftop ices like a starved piston.
TXV / orifice. Economizer dumping 40 °F OA on the coil can look like a freeze-stat trip.
Do not add gas because suction is low.

Plates that use LPS

Same number, other makers

LPS on Bryant is not the same code on these plates.