PH23A and PH51W - Mini Temperature Controller - Voltage Drop

PH23A and PH51W - Mini Temperature Controller - Voltage Drop - TB141001

Issue Date: Oct.29, 2014 (Revised March 18, 2020)

Scope: PHP-23A and PHP-51W Heaters with Mini Controller 

​Complaint:

Heater will not attempt start-up in heat mode and will not run in vent mode.

Resolution:

It has been discovered that a batch of faulty thermostats have been released. It has been determined that on some switches, the voltage signal from the switch to the ECU is too low.

est can confirm if you have a faulty Temperature Controller with a “Voltage Drop”

The following test can confirm if you have a faulty Temperature Controller with a “Voltage Drop” problem.



  1. Connect Voltmeter between Red and Black wires and note voltage.

  2. Turn Switch to Heat Position, then connect Voltmeter between Yellow and Black wires and note voltage.

  3. Evaluate:
    Difference in voltage should not exceed 2 Volts
    Voltage on Test 2 at Yellow wire should be a minimum of 9 Volts.

Corrective Action:

Conduct the above test and if faulty, contact PHP to arrange replacement. We are unable to determine the scope of this problem at this time.

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