Catalog Ordering & Shipping Electrical Tech Work Shop Tips About M.A.D.

Part TwoAMP gauge WIRING FIXES (Dodge was used for this work shop model)

By Mark Hamilton

          We have seen the weak areas, now we will make improvements.  The male/female flat blade terminals for the AMP gauge wires at the firewall connector will be eliminated–because they are the weakest link in the system.  The AMP gauge will be disconnected and by-passed–because the gauge often fails and sometimes it burns dashes.  Alternator output will be routed directly to the BAT. POS. stud at the starter relay–because it’s the most direct routing of power.  And, we will make use of both legs of the old AMP gauge circuit–because it doubles the strength of the main power-up circuit to the “welded splice,” which serves as power distribution. 


          When everything is working properly, the alternator is the source of power to the entire electrical system.  With this new system, we have alternator output delivered to the BATTERY POSITIVE stud at the starter relay.  The stud at the starter relay now becomes the “main buss” for power distribution.  Battery charging current will flow directly to the battery, via the positive battery cable.  The “welded splice” in the dash wire harness still serves as a junction for power distribution–but now we are sending power to the “welded splice” through both of the existing wires that were part of the old AMP gauge system.  And the AMP gauge is by-passed.

          The system mostly uses existing wires that were already in the wire harness.  But since we are disconnecting, bypassing, and ignoring the AMP gauge, we can rearrange the wires to form a much stronger system.  The male/female terminals at the firewall connector are also by-passed, the wires now pass directly through connector body connection.

We have also used the proper Fusible Link wires for short circuit protection.  A 14 gauge Fusible link is protecting the 10 black wire circuit to the alternator.  And a 16 gauge Fusible link protects the power-up wires to the “welded splice,” which serves as main power distribution to the dash area. 

Craftsmanship and wire splicing methods will be critically important to reliability with the new system.  We are working on wiring that must handle large amounts of electrical power every time the truck is driven.  Our work has to be good or the outcome will be no better than the weak factory system.  We have to use a few splices to complete the up-grade, and splicing is a job that not everyone does well.  Resistance at all spices and connections must be minimized.  Crimp-on butt connectors with yellow plastic insulation, wire nuts, or twisting and tapping wire together will not be reliable splicing methods.  The old method of crimp first, then solder, then insulate is still the most reliable.

The best parts for the job are non-insulated butt connectors, which are made of copper and are tinned with solder.  Good quality shrinkable tubing will insulate the splice, and a length of it must be slipped down the wire before installing the butt connector.  We will also need a soldering gun or soldering iron, and a lead/tin rosin core solder. 

After stripping the ends of the wires, we slipped shrinkable tubing down the wire.  Then we crimped the non-insulated butt connector onto the wires.  And then soldered the connection. 

Electrical tape may be used for the first layer of insulation, before slipping the shrinkable tubing into place.  (We are using this option because it provides a little extra padding and insulation over the splice.) 

     Then slide the shrinkable tubing into place, and apply heat to shrink the tubing tightly for a good seal.  A disposable lighter works well when there is no breeze.  A heat gun works very well and is safer too, as it is flameless.  Hair driers do not produce enough heat to activate the better shrinkable tubing. (The splice shown in the photos above is where we have disconnected and by-passed the AMP gauge at the dash.) 

     Using a drill slightly larger than the O.D. of a 10 gauge wire, we are drilling out one of the slots in the engine side of the firewall connector body.  A new wire will pass directly through the connector body without the weak male/female terminal arrangement.

     Both sides of the bulkhead connector must be drilled–the engine side and the dash wire harness side.     

     In the photo above, we are drilling out the dash harness side of the bulkhead connector.  Before drilling this side, check from under the dash to be sure that wires are clear at the backside.  And drill just deep enough to go through the connector–there are many wires at the other side, which could be damaged by the drill.

     This connector body is easily dismounted from the firewall by releasing the latches.  Removing the connector body and then dragging it under the dash will allow drilling it from the other side.  With either method, be sure to get the correct slot so that the holes in both of the connector bodies will be aligned after assembly.

     Often the old terminal is melted into the plastic connector body and tightly embedded.  If the terminal cannot be removed without breaking the connector body, then we can use available unused slots for the new direct pass-through. 

     We have cut the original 10 gauge black wire from the alternator to the connector, and then removed the terminal with wire remnant from the connector body.  (see arrow A)

     Splicing on a new length of wire has lengthened the original alternator output wire.  Now it is routed to the starter relay, where a fusible link will be installed.  (Arrow B points to the splice.)

     At the dash side of the firewall connector, we also cut the wire and removed the terminal from the connector body.  And we lengthened the wire at the dash side–it now passes directly through the drilled out connector bodies.  (see arrow C) 

     At the dash side of the firewall connector, we have cut and lengthened the red and black 10 gauge wires.  Both have been left long enough to pass through the holes drilled in the connector body and reach out to the starter relay area.  Plus we added an extra 12 to 15 inches in length, which will be bundled to the dash harness. 

     The extra length bundled at the dash side of the wires will provide opportunity for service work.  Should we ever need to inspect, test, or clean other terminals at the connectors, we can always remove the nylon ties and drag the extra length of wire through the connector bodies.  Then the engine side connector body may be unlatched and slipped over the 10 gauge wire for access to terminals in the connector. 

     The photo at left shows the fusible Link installations, where the new wires will connect to the battery positive stud at the starter relay.

     The red and black 10 gauge wires connect to a 16 gauge fusible link wire, which is actually identified as a metric size on this particular fusible link.  (1.0 sq mm is the metric equivalent of 16 American Wire Gauge size.)  This circuit powers up the welded splice in the dash harness, which powers up all switches, fuses, and circuits at the entire dash area.

Short-circuit protection for the black 10 gauge wire to the alternator is provided by a 14 gauge fusible link (the light colored of the two, which is actually a 2.0 sq mm metric equivalent.)

        The up-grade really is quite simple, and it does provide remarkable improvements to reliability and electrical system performance.  The Dodge alternator/voltage regulator system will perform well with the up-grade.  Expect more consistent voltage throughout the system as resistance is significantly reduced at the main power wiring. 

          Craftsmanship will have to be good, for the new system to be reliable.  We are working with the main power delivery to the entire electrical system.  Current to operate the entire system will flow from the alternator, through this circuit, every time the vehicle is driven.

          Crimp-on connectors will not be good enough!  They are prone to “Thermal Run-away” problems, which is exactly what happened to the crimped on butt connector shown in the above photo. 

          M.A.D. offers very quality non-insulated terminals made of “tinned” (solder coated) copper, which are perfect for the crimp first, then solder, then insulate with shrinkable tubing connections.  (As with the splice that shown in this feature.)

          The “tech is made simple” book, also available in through the M.A.D. catalog, teaches splicing and soldering techniques, all about the “Thermal Runaway” problem, and all about Fusible Link wires.

          And the M.A.D. catalog offers excellent wire strippers and terminal crimping tool, ideally suited for this kind of work. 


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