Copyright © 1998 General Motors Corp. L–1
WTEC II ELECTRONIC CONTROLS TROUBLESHOOTING MANUAL
APPENDIX L — EXTERNALLY-GENERATED ELECTRONIC INTERFERENCE
1–1. ELECTROMAGNETIC/RADIO FREQUENCY INTERFERENCE
All electrical and electronic systems generate electromagnetic fields that can interfere with other electronic
systems. Allison Transmission electronic transmission controls comply with Federal Communications Commission
(FCC) regulations and other guidelines concerning emitted radio frequency interference for transportation
electronics. The position of Allison Transmission Division of General Motors is that manufacturers and installers
of EMI/RFI emitting equipments are responsible for adhering to FCC regulations and other guidelines concerning
emitted radio frequency interference for transportation electronics.
Some radio-telephone or two-way communication radios (land-mobile radio), or the manner in which they are
installed, can adversely affect vehicle operation or be affected by other vehicle components. Expenses incurred to
protect vehicle-related systems from EMI/RFI emissions by radio-telephone or two-way communications radios
(land-mobile radio) or to integrate such devices into vehicles are not the responsibility of Allison Transmission.
1–2. GENERAL GUIDELINES FOR RADIO EQUIPMENT INSTALLATION
The following general guidelines for installing radio-telephone or two-way communications radios (land-mobile
radio) in a vehicle supplement, but DO NOT replace, detailed instructions provided by the radio equipment
manufacturer. Detailed installation instructions are the sole responsibility of the radio equipment manufacturer.
Experience has shown that most EMI/RFI problems can be prevented or eliminated by following the guidelines.
If EMI/RFI problems persist after following the guidelines and after ensuring the installation conforms to the
guidelines, contact the vehicle and radio equipment manufacturers for additional installation or equipment
operation instructions.
A. Transmitter Installation
1. Locate remote radio transmitters as far away from other electronic devices and as near to the side
of the vehicle body as possible.
2. Mount transceivers (transmitter and receiver in one box) under the dash so as not to interfere with
vehicle controls or passenger movement.
B. Antenna Installation
Each vehicle and body style react differently to radio frequency energy. When dealing with an
unfamiliar vehicle, test various antenna locations by using a magnetic mount antenna and checking
for adverse effects. Antenna location is a major factor in EMI/RFI problems.
C. Antenna Cable Routing
1. Use high quality, 95 percent shield coverage, coaxial (coax) cable. Route the coax well away from
any electronic components.
2. Route antenna cables as far away from vehicle wiring as possible to reduce the likelihood of the
vehicle wiring acting as an antenna for interference.
D. Radio Wiring and Connector Location
1. Connect transmitter power leads directly to the battery.
2. For transceivers (transmitter and receiver in one box) with ignition control, place a 12V power
contactor at the vehicle battery. Drive the contactor coil, through an appropriate in-line fuse, from
an ignition circuit not powered during engine cranking.
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