06-May -14
Page 3 of 4
Procedure: Testing Resistance of the Heated Zone Heaters and PRT’s
WARNING: Before proceeding, turn off the main power switch and unplug
the power cord.
Caution: Make sure you are properly grounded with an ESD strap before
continuing.
Remove the GC panels required for access to the zone heater/sensor connector to be tested.
Remove the connector for the heated zone sensor to be tested
– use an ohm meter to
measure the resistance of the PRT in question.
For heated zones the PRT is connected to the white wires on pins 2 and 3 of the connector.
The resistance of the PRT should correspond to those in the “
Table of PRT Values
”
The heater resistance can also be measured between the red wires on pins 1 and 4 – typically
23 Ω for a 70 watt heater (see table following).
With the
connector removed from the GC
, there should also be no connection to ground on
any of the four pins – this would indicate a possible shorted sensor or heater.
Table: PRT Resistance Values:
Pin 4
– Heater Ground
Pin 3
– Sensor Ground
Pin 2
– Temp Sense
Pin 1
– Heater Control
