Two Way Radios - Poor Reception: Overview
NO: 08-30-96GROUP: Electrical
DATE: Sept. 6, 1996
SUBJECT:
Radio Interference To/From Two-Way Radio Receivers
MODELS:
1995 - 1997 (BR) Ram Truck
SYMPTOM/CONDITION:
Customers may complain of intermittent poor reception on their two-way radios and/or the windshield wipers may operate intermittently during two-way radio communication (wipers off).
NOTE:
THIS CONDITION DOES NOT AFFECT THE OPERATION OF ANY AM OR FM BAND RADIO.
DISCUSSION:
Radio receivers from approximately 20 MHZ to 174 MHZ may be susceptible to Radio Frequency Interference (RFI) from the fuel pump module's motor and/or HVAC blower motor. In addition, the windshield wiper delay module may be affected by radios operating within the 20 MHZ and 174 MHZ range.
The following services are within this band range of 20 MHZ to 174 MHZ:
^ 27 MHZ Citizen Band
^ Ten Meter Amateur Radio Band (28 - 29.7 MHZ)
^ Public Service Low Band VHF (30 - 50 MHZ)
^ Six Meter Amateur Radio Band (50 - 54 MHZ)
^ VHF Aircraft Communications Band (118 - 136 MHZ)
^ Two Meter Amateur Radio Band (114 - 148 MHZ)
^ Public Service High Band (148 - 174 MHZ)
DIAGNOSIS:
Turn the ignition key to the RUN position (HVAC controls must be OFF and wipers OFF). Operate the two-way radio and monitor for RFI/static/poor reception. Turn the HVAC controls ON and operate the blower fan through the different blower fan speeds while monitoring for RFI/static/poor reception. Start the engine and monitor for RFI. Next, key the microphone and monitor for intermittent wiper operation.
If there is RFI with the ignition key turned to the RUN position (HVAC controls OFF, wiper OFF, and engine OFF), RFI is being emitted from something other than the fuel pump module's motor or the HVAC blower motor. If RFI is identified while the HVAC blower fan is operating, perform Repair Procedure A. If RFI is identified while the engine is running, perform Repair Procedure B. If the wiper motor intermittently operates during any radio operation, perform Repair Procedure C.
NOTE:
IT IS IMPORTANT TO IDENTIFY WHICH COMPONENTS ARE EMITTING RFI. AFTER A REPAIR HAS BEEN MADE, PERFORM THE DIAGNOSIS AGAIN TO IDENTIFY IF ANY OTHER COMPONENT IS PRODUCING RFI. SOME VEHICLES MAY REQUIRE ALL THREE REPAIR PROCEDURES.
PARTS REQUIRED:
1 (AR) 04883825AA RFI Filter For Fuel Pump Module
1 (AR) 04883826AA RFI Filter For HVAC Blower Fan Motor
1 (AR) 04883827AA RFI Filter For Windshield Wiper Motor Delay Module
POLICY: Reimbursable within the provisions of the warranty.
TIME ALLOWANCE:
Labor Operation No: 08-92-00-90 0.2 Hrs.
Perform Repair Procedure A
08-92-00-91 0.2 Hrs.
Perform Repair Procedure B
08-92-00-92 0.2 Hrs.
Perform Repair Procedure C
FAILURE CODE: XX - Service Adjustment