POOR RADIO RECEPTION ON DISTANT FM STATIONS. Cadillac Allante 1987

For 1990-2009 cars

# POOR RADIO RECEPTION ON DISTANT FM STATIONS

#### MODELS AFFECTED: 1987-1988 ALLANTES

Some 1987-1988 Allantes not equipped with a cellular telephone may experience Poor radio reception on distant FM radio stations This may be caused by high resistance in the antenna signal circuit or a poor antenna ground.

When diagnosing a vehicle for poor FM radio reception, perform the following checks:

#### Antenna Signal Circuit Check:

1. Have the power antenna mast fully extended. Disconnect the antenna power connector.

2. Turn key off.

3. Disconnect the antenna coax (lead-in) from the radio receiver.

4. With an ohmmeter set on the 20 ohm scale, measure the resistance from the tip of the antenna mast to the tip of the male coax connector at the receiver. The resistance should not exceed 2 ohms. If less than 2 ohms, proceed to step 7.

5. If there is more than 2 ohms, measure the resistance from the tip of the antenna mast to the fattest section of the antenna mast. If the high resistance is in this section, the antenna assembly should be replaced, P/N 22062588, which is currently available from GMSPO.

6. If the resistance is not high, measure the resistance across the coax from inside the female coax connector to the tip of the male coax connector. Replace the coax, P/N 1635449 which is currently available from GMSPO, if there is high resistance.

7. Measure resistance across the coax from outer shield of the female to the outer shield of the male. Replace the coax if there is more than .05 ohms (approximately 0) resistance.

#### Antenna Ground Check:

8. Reconnect antenna power connector.

9. Key on.

10. Lower antenna mast. Disconnect the antenna power connector.

11. Key off.

12. Remove the lower antenna attaching screws. Prevent the antenna motor assembly from contacting the vehicle body by wrapping the motor with a shop cloth.

13. With an ohmmeter set to the 2 ohm scale, clip one lead to a metallic section of the antenna tube assembly, refer to Figure 1. The other lead should be touching the sheet metal of the right rear quarter panel. There should be 0 ohms resistance between the antenna tube and the vehicle body. If there is high resistance, remove the antenna assembly and inspect the top of the antenna tube for a plastic washer that may be insulating the antenna assembly from the car body. Remove washer if present.

Vehicles equipped with cellular telephone should expect some deteriorated FM reception.

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.