Running Extra Cabling Through the P38 Firewall


Ron Beckett's Upgraded Electronics
Introduction
Getting the Cables through the Firewall
Auxiliary Fuse Box Installation


Introduction
Installation of many additional equipment items such as trailer brake controllers, CB antennae, etc often requires additional wiring to be run through the firewall/engine bulkhead. On the Classic this was seldom much of a problem due to the rather casual sealing of the firewall and abundance of holes in it. On the 4.0/4.6 the task is considerably more difficult as all cables and pipes going through the firewall are tightly sealed as well as being buried in deep layers of insulating foam. On this page, Ron Beckett kindly shares his method of running the extra cabling he needed on his Right Hand Drive 4.6 when he installed his CB, auxiliary cigarette lighter sockets, dual battery controller, and LED monitors for his EAS pump and brake pump (these upgrades are depicted in the photo at the top of this page and described in more detail on the CB installation page). To top off his installation, Ron also describes the addition of an auxiliary fusebox which provides power to all these accessories.

Getting the Cables through the Firewall
To get all these wires through the firewall, Ron ran a length of multi-core trailer wiring into the cab via the grommet behind the cooling system expansion tank. He ran the CB antenna coax the same way (see photos below). To reduce friction when sliding the cables through (and prevent the grommet being pulled out of the firewall), lubricate the cables with a small amount of liquid kitchen detergent and water. (Note -- the extra two white wires in Ron's photos below were only temporary for another job he was doing).

cable through firewall

cable behind coolant tank


When the tank is lifted out of the way on RHD models (it just clips in), carefully remove the clips holding the insulation in place.  This will give access to the grommet.  On a LHD car, you can probably also access the matching grommet on the LH side.  When you look up under the dash (left hand photo) you can see where the wiring loom comes through that grommet.  Because Ron knew what was behind the grommet (from looking at a wrecked car), he was able to run an electric drill (not for the faint-hearted!) through the grommet which has an odd-shape and thus has a place where one can drill it.)

Auxiliary Fuse Box Installation
Ron also added an auxiliary fusebox to supply all the new accessories; he found a long narrow unit that fitted nicely in the space between the coolant expansion tank and the side of the engine bay (see photos below). This location is handy to the battery to ease tapping into it.

Auxiliary Fuse Block

Auxiliary Fuse Block



 

 

 

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Page revised February 1, 2012