Honeywell T7351 User Manual

63-2666—02

18

Heat will not come 

on.

No power to the thermostat.

Check that X terminal is connected to the system 

transformer.
Check for 24 Vac between X and RH terminals.
If missing 24 Vac:

• Check if circuit breaker is tripped; if so, reset circuit 

breaker.

• Check if system fuse is blown; if so, replace fuse.

• Check if the HVAC equipment power switch is in the Off 

position; if so, set to the On position.

• Check wiring between thermostat and HVAC equipment. 

Replace broken wires and tighten loose connections.

If 24 Vac is present, proceed with troubleshooting.

Thermostat minimum off time is activated.

• Wait up to five minutes for the system to respond.

• Configure heating response.

System selection is set to Off or Cool.

Set system selection to Heat or Auto.

DAT high limit has been reached, or 

OAT lockout is engaged.

• If the setpoints are correct, do nothing.

• Adjust or disable DAT high limit and/or OAT lockout.

• Check HVAC equipment to ensure proper operation.

Cooling will not 

come on.

No power to the thermostat.

Check that X terminal is connected to the system 

transformer.

Check for 24 Vac between X and RC terminals.

If missing 24 Vac:

• Check if circuit breaker is tripped; if so, reset circuit 

breaker.

• Check if system fuse is blown; if so, replace fuse.

• Check if the HVAC equipment power switch is in the Off 

position; if so, set to the On position.

• Check wiring between thermostat and HVAC equipment. 

Replace broken wires and tighten loose connections.

If 24 Vac is present, proceed with troubleshooting.

Thermostat minimum off time is activated.

• Wait up to five minutes for the system to respond.

• Configure cooling response.

System selection is set to Off or Heat.

Set system selection to Cool or Auto.

DAT low limit has been reached, or 

OAT lockout is engaged.

• If the setpoints are correct, do nothing.

• Adjust or disable DAT low limit and/or OAT lockout.

• Check HVAC equipment to ensure proper operation.

System indicator 

(flame: heat, 

snowflake: cool) is 

displayed, but no 

warm or cool air is 

coming from the 

registers.

The call for heat or cool is not yet given.

Check if any stage indicators (dots next to the system 

indicator) are displayed. With no display of stage indicators, 

no call for cool/heat via relay is yet given.

Conventional heating equipment turns the fan 

on only after the furnace has warmed to a 

setpoint.

Wait one minute after seeing the on indicator and then 

check the registers.

Heating or cooling equipment is not operating. Verify operation of heating or cooling equipment in Test 

Mode.