MFJ-4402 Mobile Transceiver Protector
Instruction Manual
© 2012 MFJ Enterprises, Inc.
9
SCHEMATIC
TROUBLESHOOTING
Fuse Blows
in MFJ-4402
Short in line to the radio.
Radio drawing too much current.
Multiple Radios drawing too much
current.
Overvoltage surge
Fix shorted wires
Fix Radio
Use only one radio at a
time in transmit to keep
total current below fuse
rating.
Have the electrical system
in the car checked out to
identify and fix the cause.
Positive Fuse
blows in the
line at the
battery
Short in the line to the MFJ-4402
Find and repair short in
cable
Negative
Fuse blows
in line to
battery
Battery ground loose or
inadequate.
Repair ground in the
vehicle.
Delay time
too short or
long
Adjust the time delay control on the
MFJ-4402
Cutout
voltage
wrong
Adjust the LV SET control.
See the radio owners
manual for the minimum
level recommended.
Radio still
looses
memory
Check radio memory battery if one
to make sure it is still good.
Radio requires voltage to keep
memory.
Radio may have internal problems
in the control circuits.
Battery life is normally 5 to
10 years.
Some older radios have a
separate line to hold up
memory that may need to
be connected.
Check out the radio to
insure proper operation.
