HIGH TEMPERATURE OR OVERHEAT CONDITION

MODELS: ALL 1982-85 C/K 2500-350O UNITS BUILT BEFORE 1/1/85, WITH 7.4L (454) ENGINES

This bulletin is being released to provide information for adding an electric cooling fan that will provide additional cooling to 1982-1985 C/K 2500-3500 models with the 454 engine. This information is a supplement to Truck Service Bulletin 85-B-86, dated June, 1985, and is not intended to replace that bulletin.

Effective 1/1/85, trucks built with the 454 engine and H5D emissions equipment are also built with an electric cooling fan. This fan is designed to provide additional cooling at low speed vehicle operations, at extended idle, and stop and go traffic conditions, etc.

If a vehicle has a low speed overheat condition and has been modified using the inforrnation in Truck Service Bulletin 85-B-86, and additional cooling is required, use the following information and illustrations to install the electric cooling fan.

Parts Information

Quantity Part Number Description -------- ----------- ----------- 1 15593566 Electric Fan 1 14078902 Fan Relay 1 14080661 Temperature Sender 1 12064526 Harness Assembly 2 15599042 Bolts - Relay 4 11504689 Bolts - Fan 10 11501906 Tie Wraps

INSTRUCTIONS

1. Disconnect battery cable.

2. Remove grill assembly.

3. Set fan in position and mark location for mounting screws. Remove fan and drill holes for fan mounting.

CAUTION

MUST BE TAKEN NOT TO ALLOW DRILL TO HIT AIR CONDITIONING CONDENSER OR RADIATOR.

Use either a drill depth guide or wrap tape around drill bit for a STOP (See Figure No. 1).

4. Install fan assembly (See Figure No. 1).

5. Drain cooling system.

6. Install fan relay (See Figure No. 2).

7. Install harness (See Figure No. 2).Make sure harness is fastened to fender and radiator support and away from sharp edges.

8. Install sender in right cylinder head (See Figure No. 3).

9. Route fan harness along side of engine harness and attach to distributor, junction block, and to engine temperature sender. Fasten fan harness to engine harness with tie wraps (See Figures No. 4 and 4A).

10. Refill cooling system.

11. Reconnect battery cable.

12. Start engine, idle, and test the function of the cooling fan (make sure fan is blowing air through radiator, if fan is blowing in the reverse direction, switch the wires in the fan harness connector at the motor). Fan should come on when engine reaches about 225 DEG F- 240 DEG F.

13. If fan checks OK, reinstall grill and check for any coolant leaks.

Labor Time to perform this procedure is 1.2 hours.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.