1995/11/06 Caterpillar

325 Excavators;
D20D, D250D Articulated Trucks;
960F Wheel Loaders Powered By 3116 Engines With Jacket Water Aftercooler (JWAC)

Reference: Service Magazine, September 27, 1993, Pages 18-20, "Dealer Installed Air Inlet Heater Starting Aid Available".

During cold weather conditions, an Ether starting aid provides improved startability. However, some customers prefer not to use Ether until temperatures become extremely cold.

As an alternative on-board starting aid, Caterpillar has released an Air Inlet Heater (AIH) that is adaptable to the above machines that are equipped with a jacket water aftercooler.

The AIH system includes a battery-powered heating element (heater assembly) mounted in the air inlet system between the aftercooler and the inlet manifold. The heater is powered by the same batteries used for the electric starting motor. A relay (switch) is used to turn on the power to the heater. The heater is grounded to the engine which is grounded to the frame and battery by the starter ground cable. The operator manually controls the AIH system by using a push-button switch in order to activate the power relay. An indicator lamp is recommended in order to visually alert the operator when the AIH system is activated. The heater must be preheated up to 30 seconds before engine cranking. When the engine is cranked, air flowing past the heater element is warmed. The warm air entering the combustion chamber helps the engine start more quickly with less cranking time and run more smoothly after it starts. In addition to preheating the element, the AIH can be used during cranking and after starting, up to three minutes, in order to help the engine run more smoothly and reduce white smoke. Normally, the battery power used for preheating is less than the additional battery power that would be needed for longer cranking time if the AIH was not used in the cold weather.

Parts required depend upon the engine configuration and system voltage (either 12 V or 24 V). There are two basic engine configurations, depending upon the model. The configuration must be determined before ordering parts:

* with vent line: 325 Excavator, D20D and D250D Articulated Trucks

* without vent line: 960F Wheel Loader

The Reference article provides a general schematic diagram for guidance in wiring the AIH system. However, due to differences in wiring of various applications, it is impossible to provide specific instructions for individual engine applications and machine models. It is the dealer's responsibility to assure proper wire lengths and wire clip locations. The dealer must determine mounting positions of the relay, indicator lamp, pushbutton switch, and make any necessary brackets. The Reference article provides a suggested list of electrical items for wiring the AIH system.

Note 1: Adding the AIH moves the engine aftercooler 25 mm (1.0 in) to the right. Prior to installation, verify that there is adequate clearance for the aftercooler in the installation, including the exhaust elbow, piping, etc. There must be clearance for normal engine movement on its rubber mounts.

Note 2: Some earlier aftercoolers contain an inner core which extends (protrudes) past the mounting surface of the aftercooler and a short distance into the inlet manifold. Earlier aftercoolers which have the extended core cannot be used with the heater assembly because the protruding core will interfere with the heater assembly. In such cases, a new aftercooler must be used. The cores of later aftercoolers do not extend past the mounting surface. The aftercooler must be removed to determine if the core extends past the mounting surface.

Note 3: For the 960F Wheel Loader, the AIH is available from the factory as an installed attachment with automatic control by the auto-shift controller.

Note 4: After installation of the heater assembly, the turbocharger compressor will not align properly with the connection to the aftercooler. Slightly loosen the bolts which hold the compressor housing. Rotate the turbocharger compressor housing outward approximately 15 degrees in order to correctly align with the aftercooler. Then, install the connecting hose. Lastly, retighten the bolts.

Note 5: Adding the heater assembly results in misalignment of the aftercooler coolant connection to the water temperature regulator housing. A new 45 degree nipple and formed hose are needed. The heater is grounded to the cylinder head, using a stud-bolt in order to replace an intake manifold bolt at the rear of the engine.

The following Illustration 1 and Chart A provide the major engine parts needed in order to mount the heater assembly.

Illustration 1. Location of new parts within 106-9086 Heater Group (Air Inlet): strap (1). stud (2). washer (3). nut (4). gasket (5). heater assembly (6). seal (7). nipple (8). bolt (9). hose (10). hose clamp (11).

For the 325 Excavator and D20D and D250D Articulated Trucks, additional parts may be needed in order to replace the steel aftercooler vent line, if so equipped. Some early 325, D20D, and D250D machines may not contain this steel vent line from the top of the aftercooler to the jacket water outlet pipe. When the AIH heater assembly is installed, the steel tube will no longer properly fit, and must be replaced with a flexible hose and connector.

The following Illustration 2 and Chart B provide the major parts needed in order to replace the aftercooler vent line.

Illustration 2. Location of new parts within a typical aftercooler vent line: Right Side View: connector (1). seal (2). valve assembly (5). hose assembly (6). Front View: connector (3). seal (4).

The Reference article provides information on electrical items, installation tips, and wiring schematic.

If the machine is equipped with an automatic ether injection system, then it may be used with the AIH system. For such machines, the ether injection nozzle must be a 180 degree dual-spray orifice located in the engine inlet manifold and oriented to spray toward the front and rear of the engine (not toward the heater element). Ether should be injected only when the engine is cranking. It should not be injected when the engine is stopped. (For details and part numbers concerning the ether injection nozzle, refer to Installation Tips within the Reference article.) If an existing ether atomizer nozzle is removed and relocated to the inlet manifold, install a plug in the original location in order to prevent the entry of dirt.

Illustration 3. Image of 4P-6422 Film (Warning)