Re: Putting GPS in a new freight liner

["Bill" <billnomailnospamx@xxxxxxxxx>]

"nick markowitz"  wrote in message
> One of my customers asked me today to install a GPS/Alarm and CB radio
> on there new MK4 freight liner box truck what a pain the freight
> liners are now all computerized and trying to get something hot when
> key is turned is a real pain use to be able to go off fuse block not
> now luckily i called freight liner and was told to hook into radio
> which has always hot and key hot which solved problem.
>

New vehicles have just about everything on running on computers and have
multiple local area networks (modern vehicles have 24 to 80 computers and 3
local area networks). And existing fused circuits on vehicles are designed
to handle ONLY the existing electrical loads connected. This includes the
size of the fuse, the size of the wire used for the circuit, and a 20%
minimum "leeway" overdesign of amperage capacity for the circuit.

With that said, before adding anything electrical to a new vehicle, you are
best to get the factory electrical diagrams manual for the vehicle, turn on
everything connected to a particular circuit, measure the amperage used,
determine the amperage draw of whatever you are installing (use amp meter),
then determine if the existing circuit will be able to handle the load and
still have a 20% overdesign leeway.

If not, then install a new fused circuit with the proper fuse and wire size
for the amperage load and switch this circuit on with a "continuous duty
rated relay" powered by the existing circuit.

If a fuse blows on a modern vehicle and that fuse also goes to a computer,
and that computer has anything to do with local area network communications,
then the vehicle will NOT run! (Or if you connect a wire to a network
communication wire, this will disable many computers which are running on
that network - the vehicle will not run!)

Wire gauge sizes and amperage...
http://www.offroaders.com/tech/12-volt-wire-gauge-amps.htm

This site has factory documentation online for passenger vehicles, I don't
know if they also have this for semi trucks or if there is a similar
service...
http://www.alldata.com

The above costs money - if they want it done right you need the factory
documentation electrical diagrams and the customer needs to pay for this!

An amp meter which will measure any DC amperage on a modern vehicle...
(Many multimeters can only measure up to 10 amps.)
http://www.amazon.com/gp/product/B000XW6AYU?