Component Tests and General Diagnostics

The DRB-III(R) tester is programmed to allow the technician to turn each cabin heater relay ON and OFF at a predetermined number of seconds. During this point, a voltage drop across each relay can be measured in order to determine whether they are functioning properly.

Checking the glow plug heating element entails measuring the resistance across each glow plug at room temperature (appx. 23 °C, 74 °F). The technician should unplug the 4-way cabin heater connector from the headlamp/dash wiring harness at the rear of the engine (rearward in vehicle above the exhaust manifold). Using an ohm-meter, measure the resistance across each glow plug by touching one probe to the aluminum cabin heater housing (ground) and the other probe to one of the terminals in the female cabin heater connector corresponding to each plug (pin 1= glow plug 1, pin 2=glow plug 2, etc.). Each heating element is functioning properly if the measured resistance is between 250 - 800 Ohm (0.25 - 0.8 Ohm) at room temperature (23 °C, 74 °F).

If one or more heating elements has a measured resistance outside this range and is not functioning properly then the entire heater assembly must be replaced.