Positive Crankcase Ventilation: Testing and Inspection

Chart C-13:

Crank Vent Heating Element:

CIRCUIT DESCRIPTION
The crankcase ventilation heater assembly is used to prevent icing in the crankcase ventilation system. The heating element inside the vent hose is used to prevent icing from the oil/air separator to the intake manifold. The heating element consists of two parallel wires that extend the length of the vent hose. One wire supplies the current when the ignition is turned "ON" while the second wire provides a constant path to ground. Although the wires are not physically attached, the material between the two wires is conductive. Current is passed through the material between the wires. As the material is heated, electrical resistance increases and current flow decreases. When the material is cooled, electrical resistance decreases, current flow and heat output increases. By this means, the temperature of the heating element is controlled to maintain approximately 115°F.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. This step verifies voltage is present to the crankcase ventilation heater assembly system.
2. This step insures a good path to ground in CKT 150.
3. This step identifies a visual failure.
4. This step identifies an open, or out of range crankcase ventilation heater element.
5. This confirms that the crankcase ventilation heating element is operational and is functioning properly.

DIAGNOSTIC AIDS
Check to insure that both battery and associated vehicle electrical connections are clean and tight. The electrical connection in the electrical system could lead to voltage spikes in the crankcase ventilation heater assembly system, causing damage to the crankcase ventilation heating element.