How to Diagnose a Heater Core with Temperature Testing Tool: 5811585
gpd’s Temperature Testing Tool, 5811585, is a simple tool that takes the guess work out of temperature diagnostics. It can be used to identify restrictions or poor air flow at the condenser as well as evaporator flooding levels on systems with an orifice tube, expansion valve performance, and receiver drier refrigerant flow. This tool can also be used to diagnose a blocked heater core or bad thermostat.
Heater Core and Thermostat Temperature Diagnosis:
To determine if the thermostat is functioning properly or if the heater core has an internal restriction, connect one wand to the inlet of the heater core (either clamp on to the exposed metal or heater hose) and the second to the outlet.
190°-210°F Temp. reading at inlet means the thermostat is functioning properly.
If temp. at outlet is 10°-25°F cooler than inlet, the heater core is functioning properly.
If temp. at outlet is 50°-80°F cooler than inlet, inspect the heater core for a blockage/ restriction.
If the heater core does not have a blockage/restriction, inspect the blend door/temp. actuator for failure or a broken actuator door.