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Low Body Voltage

1962 to 1978 Mopar Products

 There are quite a few places this can happen.  Itís all in the connectors and quality of the remaining wiring.  This will be sort of generic, there is a breaking point in production concepts of some of the cars, but when I am done here, I think youíll see what I mean. 

Low Body voltage is a problem.  It tends to degrade connectors and wire because of over heating.  But!  If you see burned insulation on wires, near a connector, you have found one of your problem spots.  This is also true for shorts, which burn wires. 

Letís list the tools you need.  Besides the obvious screw drivers and pliers needed to access the wiring locations, it would be a good idea to have a test light, volt meter, soldering gun and  Flux Core solder.  Donít forget a drop light or flash light. 

If you know you are going to be working on a power feed problem, get some #10 wire.  It can be purchased in different colors and in 10- foot lengths.  I suggest Red and Black and 25í packages. Invest in some shrink-wrap for the wiring as well. 3/8í is good for #10.   Shrink-wrap, while expensive, has great insulation properties, and will give you a much neater job when done.  Get some shielded solder-less connectors and butt connectors.  You want both male and female spade connectors in the YELLOW jacket for #10 wire.  Blue for 12 to 18 Ga.  Try to buy the ones with the plastic shield around the spades as they will be safer and save you time shielding them.  Electrical tape has a tendency of pealing back. 

If you are new to auto electrics, I suggest you read this link first:

Basic Wiring Tips   Click here

Get your tools and supplies together before you dive into this 

So letís review the symptoms.

A.  Lights are dimming

B.  Ammeter is either over charging or under charging

C.  Nothing works

D.  Discharges as you add accessories 

99% of the time, all of these symptoms is as a result of poor connections.  Keep in mind; you may have damaged other connections on accessories.  This is common as well.

 OK so letís assume you have eliminated the obvious . . .Bad Battery, Bad Alternator, wiring under hood is in tact.

 Hereís what to look for.

  1. Check the pigtail connection on your battery.  If you have a replacement connector, make sure itís tight and clean.  NO CORROSION!  Make sure you have good connections in the battery connector.  If in doubt, re-strip the wires and replace the connector,
  2. Follow the pigtail to the fusible link connector.  Take it apart and be sure the connector isnít burned and is tight.  If not, it will need to be replaced.
  3. Now look at the fusible link itself.  Run your fingers down it and feel for knots or lumps.  The knots or lumps usually mean there is corrosion and should also be replaced.  Please note, some cars do not have a link in there.  The link could be at the bulkhead connector or none at all. (Early 60ís)  It is a good idea you replace the link anyway.  They tend to degrade over the years and leak voltage or could disintegrate without notice.
  4. Check the connector at the other end of the link.  Inspect it for tightness, corrosion, or burning.  If any of this is present, this too needs to be replaced.
  5. Continue to follow the heavy wire to the bulkhead connector.  This is where it gets interesting.  All of what you have looked at so far is very important.  This is where the engine compartment feeds the car and all itís accessories.

    Please note:  The images provided below mostly came from the same harness.  The exception is the image with the fusible link on the bulk head connector.  These will show you what can happen if you leave a low voltage problem unattended too long.

    Here the link has been repaired where the quick connector was probably burned.  The mechanic did the right thing by crimping and soldering.  But the link has developed corrosion at the repair point.  Usually Links are degraded when this is scene.  This particular situation was a result of over heating and using acid core solder.

    This is from a 70 Plymouth.  The red circles indicate over heating on this harness where the fusible link is fed from the battery.

    1. Disconnect the battery
    2. Remove the plugs from the bulkhead connector.  They are keyed, so you canít put them back in the wrong places.

      No apparent Damage here

    3. Look at the spade connectors in the plugs.  Look for corrosion, or melted plastic.  Particularly around the bigger wires.  The Bigger wires are the main power feeds for the charging system and body feeds.  If you see browned, corroded plastic or wire insulation, this is a place you need to pay some attention and probably cause for your problems.  However, I remind you, any poor connection in this primary circuit is critical.  Letting it go will only make it worse in time.  You also leave an opportunity for components to fail prematurely.
    4. Now the fun part.  Under the dash, On the C bodies, the bulkhead connector is behind the fuse block.  May be the same on the early 60ís, but youíll know when you are under there.  Here again you need to inspect all your connections on the back side of the connector.

      Here an accessory wire has been burned by an over load.  This happens to be the feed to the heater blower.

      Heater Connector.  I would examine your blower switch too.

Earlier 62 to 69 (Maybe 70) the Ammeters were used in the primary circuit.  The whole load ran through the ammeter.  The power went in one end, registered on the meter, and cam out the other end, feeding everything, including the battery.  From 70 on up, the cars had a parallel circuits.  One circuit ran from the alternator back to the battery.  The ammeter was piggy backed on that with a shunt.   The ammeter was not used as a primary supply device, but showed the usage of current without being in the line directly.  (Did that make sense?)  Well anyway, the whole car didnít run through the ammeter.  The battery circuit ran into the body through a separate wire, (The one with the fusible link) which fed the ignition switch and accessories.

    1. So far, weíve covered half the trouble spots.  On the cars with the

Column ignition switch, the connector is at the bottom of the column.  The tilt column has the whole switch at the bottom of the column.  This is better as it eliminates a bunch of wire and a connection block.  These are trouble spots also.  Most are white plastic, so it will be easy to see damaged wiring or connections.  Like the bulk head connector, look for burned plastic, connections or insulation.  These hot spots will cause resistance and only continue to burn.

This is a column ignition switch connector.  Located under the dash next to the steering column.  The red wire is the primary ignition feed.  Obviously the damage is pretty bad.  This is from the same harness as the burned heater connector (Above) and damaged fuse box.

    1. On dash ignition switches, the connections are on the back of the switch.  You need to remove the switch and examine the connections and wiring.  These connections are held on with nuts.  The nuts tend to loosen in time and again may cause hot spots.  Examine these connections and wiring as before.  If possible, I suggest you replace the ignition switch while there.  This way, you are sure there is no internal damage causing high resistance.
    2. The ammeter is another story.  As mentioned, the earlier Mopar vehicles used the Ammeter in the primary circuit.  The car was dependant on the meter and the connections on the back.  Here again, you will have to remove the meter from the dash, or pull the cluster to check the connections.  This is usually another trouble spot.  Some people bypass the meter by putting the two wires on one terminal.  However, if the connections are burned and there is burned insulation, you need to replace the connections. Before doing that.

 More to come   Don't wait for me!





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