REDUCED HEATER SYS. PERFORM. NEW HEATER OUTLET DUCT/PROCED.

Model and Year: 1990 W CARS

Comments on the above vehicles about heater system performance such as being slow to warm up or inadequate heat may be received from some customers.

If the heater system is operating properly and the engine temperature is in the operating range, the cause of the condition may be reduced air/heat distribution from the heater outlet.

This condition may now be addressed by using the following service parts and procedures.

The parts and procedures for the W Car without the performance audio system are as follows:

PARTS

QTY. PART NO. PART NAME ----- -------- ----------

1 52452131 Heater Outlet Duct 26 in. *06375 3M #4508 Scotchfoam Black Vinyl Foam Tape * Purchase Locally

Parts are currently available from GMSPO.

PROCEDURE:

* Remove the R.H. hush panel,see Figure 3.

* Remove the adapter duct, see Figure 1.

* Remove the heater outlet duct, see Figure 1.

* Remove the two top screws from the module, one on each side. These two screws will be used to mount the new heater outlet duct, see Figure 2.

* Install the 1/8 X 3/4 in. foam tape to the grooved mounting surface of the new heater outlet duct, approximately 11 3/4 in of tape across the top of the outlet duct and 7 in.of tape on each side. Trim off excess tape.

* Install the new heater outlet duct to the module, see Figure 2.

* Install the adapter duct, see Figure 1.

* Cut off a two inch square piece of the R.H. hush panel as indicated in Figure 3. This may be done with a saw blade or a bench grinder.

* Install the R.H. hush panel.

Labor Operation Number: T1510

Labor Time: 0.4

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.