Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Catalog No. 04-53370001-01
Printed in U.S.A.
Form 37HS-10SI
Pg 32
8-18
Replaces: 37HS-1SI
© Carrier Corporation 2018
Table 10 — Troubleshooting Chart
SYMPTOM
POSSIBLE CAUSE
CORRECTIVE PROCEDURE
ROOM TOO
COLD
Thermostat Setting Incorrect
Check thermostat setting—move thermostat lever slightly toward red area. If unit
shuts off, leave in this (or in an intermediate) position. See Fig. 42.
Volume Controller Setting Incorrect
Check actual volume controller setting vs design cfm — readjust volume controller
setting. Minimum flow set above stop.
Minimum Flow Set Above Internal Stop
Turn minimum flow star wheel counterclockwise to zero position.
Supply-Air Temperature Too Low
Check actual temperature of supply air vs design supply air temperature. If required,
raise supply-air temperature.
Controls Improperly Seated
Check connections between filter and plenum, volume controller and filter, filter and
bellows.
Tubing Loose or Kinked
Check interconnecting tubing between units. Refer to job drawings; check control
arrangement — secure as required.
Plugs and Caps Not Installed Properly
Check cap on bellows end connection. Check caps and plugs on filter.
Unit Controlled by More than One Set of
Controls
Check job drawings for proper control arrangement—make changes as required.
Filter Clogged
Visually check filter media — replace only if excessively dirty. (Normally, filter will not
require replacement.)
Volume Controller Defective
Check volume controller operation with thermostat lever set at extreme blue area —
replace volume controller if unit airflow does not decrease when cfm setting is
decreased.
Thermostat Defective
Check thermostat operation — replace thermostat if temperature at thermostat is
below 75°F and airflow does not shut off when lever is at extreme red area.
Bellows Defective
Check bellows — remove controls, cap one end of bellows, connect tube to other end
and inflate until unit shuts off. Trap air in bellows. If unit flow increases, bellows is
defective — replace.
Supply Pressure to Filter Not Correct
Remove controls including filter. Check pressures at end plug. There must be
pressure reading at each connection. Top connection pressure reading must be
higher than low connection pressure reading. If pressure readings are the same or
opposite of above — move controls to another unit.
ROOM TOO
WARM
Thermostat Setting Incorrect
Check thermostat setting—move thermostat lever slightly toward blue area. If air is
discharged from unit, leave lever in this (or in an intermediate) position. See Fig. 42.
Volume Controller Setting Incorrect
Check actual volume controller setting vs design cfm —readjust volume controller
setting.
Supply-Air Temperature Too High
Check actual temperature of supply air vs design supply air temperature. If required,
reduce supply-air temperature.
Duct Pressure Incorrect
Measure duct pressure — verify per Table 6.
Unit Controlled by More than One Set of
Controls
Check job drawings for proper control arrangement—make changes as required.
Tubing Loose; Control Caps Not Installed
Properly
Check interconnecting tube between volume controller and thermostat. Check caps
on volume controller at thermostat connection.
Volume Controller Defective
Check volume controller operation with thermostat lever set at extreme blue area.
Replace volume controller if airflow does not increase when volume controller cfm
setting is increased.
Thermostat Defective
Check thermostat operation — replace thermostat if temperature at thermostat is
above 69°F and the cfm is not at design requirements, although lever is at the extreme
blue area.
