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Wiring trouble 1970 dodge challenger

Nathan Pardo

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So, I have a big problem with my wiring. Before I bought the car, the previous owner made a mess out of the wiring. I have worked on many mopars before, but never to this extend with the wiring. anyhow, the blinker lights don't work, none of the gauges work, one of my headlights is brighter than the other and if I switch the wires around its the same thing. The bigger problem is that I was testing for electricity for my dash to work. I found out that the negative (black) wire to the amp meter had electricity. I couldn't understand why? after a while experimenting with the car found out that whenever the red wire was connect. I would have electricity going through the black wire. So smart me decide to connect the black wire and the red wire to a separate volt meter. which I later found out its a BIG NO! The fusible link in my car was bypassed and electricity was going through everywhere. luckily I jumped out and disconnected the battery just on time before anything caught on fire. The red wire going to the amp meter melted the insulation plastic. I bought a new starter relay, fusible link, alternator regulator, inspected all the wires to see if any other burned. And only the red wire going to the amp meter burned. It didn't burned all the way through, so I cut it to where it stopped melting. anyhow the car doesn't have any electricity inside the car. I replaced the battery and nothing. Checked if the electricity was constant to the starter, starter relay, and going to the bulkhead but after that nothing. I didn't have time to inspect anymore, I'm a pre-Med student so my time is limited. Did I killed my cars wiring forever?
 

rklein71

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I followed this for my wiring. It gives you information on the weakness of Mopar's design relating to dash wiring and ammeter.
Catalog
 

72RoadRunnerGTX

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The black wire at the ammeter (it is not a volt meter, it’s an ammeter, both terminals will have voltage) is NOT a ground and should never be grounded. The black wire is the alternator side of the ammeter, yes, voltage will be present. If it is currently not showing voltage present, or is disconnected from the ammeter, the electrical loads of the vehicle will not have voltage as well, all loads are spliced into the black wire in the dash harness.
 

Nathan Pardo

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The black wire at the ammeter (it is not a volt meter, it’s an ammeter, both terminals will have voltage) is NOT a ground and should never be grounded. The black wire is the alternator side of the ammeter, yes, voltage will be present. If it is currently not showing voltage present, or is disconnected from the ammeter, the electrical loads of the vehicle will not have voltage as well, all loads are spliced into the black wire in the dash harness.
That make so much sense. So if neither the Red wire or the Black wire are connected to the back of the cluster, then the car won't have any power, Right?
 

72RoadRunnerGTX

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Yes, the red wire is the battery side of the ammeter, if either of the wires are disconnected, the car will be dead. If for some reason you wish to by-pass the ammeter, connect the two wires together and insolate to be sure they will never touch the cluster frame.

The ammeter gets a bad rap on these forums, not very well understood for the most part. Tight, but not too tight, connections, good mounting insulators, the ammeter is the most actuate gauge to real time battery charge/discharge state and is perfectly safe.

BTW, on these cars, never assume a black wire is negative or is a ground of some kind. There are several circuits running positive voltages over black wires.

For that matter, with these cars, you can’t even count on all segment wiring of the same circuit retaining the same color code for the entire circuit.

I disagree the basic premise of the “Mad Electrical” article linked above and its condemnation of all versions of Mopar’s ammeter-based charging systems. With one exception, the late seventies attempt by Dodge to make a plastic framed ammeter for their trucks, that was a mistake. Most ammeter connection problems can be traced to poor past maintenance/service work, nut either over tightened or left too loose. Over tightened nuts will crush the fiber insulators, loose nuts will lead to heat build-up that will burn the insulators. That can lead to the possible stud to cluster contact, more heat.
 
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Nathan Pardo

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Yes, the red wire is the battery side of the ammeter, if either of the wires are disconnected, the car will be dead. If for some reason you wish to by-pass the ammeter, connect the two wires together and insolate to be sure they will never touch the cluster frame.

The ammeter gets a bad rap on these forums, not very well understood for the most part. Tight, but not too tight, connections, good mounting insulators, the ammeter is the most actuate gauge to real time battery charge/discharge state and is perfectly safe.

BTW, on these cars, never assume a black wire is negative or is a ground of some kind. There are several circuits running positive voltages over black wires.

For that matter, with these cars, you can’t even count on all segment wiring of the same circuit retaining the same color code for the entire circuit.
Ah ok. That makes sense. Thank you so much for your help! I have another question though. how do I make my gas gauge work? it has a new sending unit. but nothing. And why one of my headlights is brighter than the other one. And my turning lights never work, and I do have emergency lights and brake lights.
 

Nathan Pardo

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One issue at a time, what dash do you have? Rallye or standard? Do the other gauges work, temp and oil pressure?
Standard, I know they worked because before breaking in my 440 whenever I turn on the key the gauges would move. It has a light for oil pressure, which comes on from time to time. I have an actual oil gauge that reads from 40 to 60 psi most of the time.
 

moparleo

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Some members may disagree with my advice at this point. Save up your money and buy a new dash and engine harness. This will eliminate anything hidden under the insulation, ( broken, pinched wire) problems that you can't see from the outside. Any burnt, melted wires, connectors etc.... I recommend the ammeter /voltmeter conversion. Other members say that it is just maintenance. I don't know of anyone who does proper electrical maintenance on their cars. The new harnesses will be fresh wires and insulation/connectors. The stock wiring is now 48 years old. The new harnesses from M-H or YearOne are factory replacement type with all factory colored wires and connectors. They are labeled where to go, so no guessing or burned up stuff. The turn signal switch inside of the steering column feeds the power to the turn signals and btake lights. I will send you some electrical links for Mopars. Read them completely and make up your own mind what to do with the info. Electrical systems and grounds especially have always been a weak point on Calssic Mopars. So clean all connections including bulb sockets. Replace all bulbs with new, high quality parts. Wagner, etc... No Asian or Chinese. European are good usually nickel plated to prevent corrosion. Use dielectric greas on all connections. It does a couple of things. #1 it water proofs the connection, #2 it eliminates air contamination of the connection ( read corrosion ) and makes disconnecting any wires much easier in the future since the connections won't corrode stuck.
Always disconnect your battery including the positive side before working on your electrical system, for obvious reasons. A fire extinguisher is good to have on hand for many repairs.
Vintage Chrysler electrical repairs and updates
Vintage Chrysler electrical repairs and updates (part 2)
Improved Wiring for older Mopars
Catalog
https://www.rt-eng.com/rte/images/e/e5/LimiterManualIVR3_D.pdf
http://moparconnectionmagazine.com/...-restoration-turn-signal-switch-installation/
 
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Nathan Pardo

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Some members may disagree with my advice at this point. Save up your money and buy a new dash and engine harness. This will eliminate anything hidden under the insulation, ( broken, pinched wire) that you can' see from the outside. Any burnt, melted wires, connectors etc.... I recommend the ammeter /voltmeter conversion. Other members say that it is just maintenance. I don't know of anyone who does proper electrical maintenance on their cars. The new harnesses will be fresh wires and insulation/connectors. The stock wiring is now 48 years old. The new harnesses from M-H or YearOne are factory replacement type with all factory colored wires and connectors. They are labeled where to go, so no guessing or burned up stuff. The turn signal switch inside of the steering column feeds the power to the turn signals and btake lights. I will send you some electrical links for Mopars. Read them completely and make up your own mind what to do with the info. Electrical systems and grounds especially have always been a weak point on Calssic Mopars. So clean all connections including bulb sockets. Use dielectric greas on all connections. It does a couple of things. #1 it water proofs the connection, #2 it eliminates air contamination of the connection ( read corrosion ) and makes disconnecting any wires much easier in the future since the connections won't corrode stuck.
Vintage Chrysler electrical repairs and updates
Vintage Chrysler electrical repairs and updates (part 2)
Improved Wiring for older Mopars
Thanks man, I really appreciate the help. I would of not be able to figure this out on my own.
 

72RoadRunnerGTX

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Start with these tests

20180925_205812.jpg
 

72RoadRunnerGTX

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If the gauge does respond, there is an open between the gauge and the sending unit. Put the blue wire back on the gauge, ground the blue wire at the sender, still no gauge response, check continuity on the blue wire to the fuel tank sender. There is one connection on this circuit (blue wire) in between the gauge connection and the sending unit. The dash harness to rear body harness (behind left kick panel) 6-way connector. Verify that connection.
 

gs73rallye

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As a Mopar mechanic in the 70s, as far as the gas gauge, first check the ground strap on the fuel line at the tank. The sending unit has the o ring which insulates it from ground. there should be a flat metal ground strap going from the sending unit to the fuel line at the rubber hose. Also, Mopar gauges ground to full, open to empty. GM does the opposite.
 

72RoadRunnerGTX

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The sender/pick-up would not be insulated from the tank by the sender seal if the sender retaining ring is in place. The fuel line clip-on ground strap insures a ground path for the sender to the fuel line in the event the fuel tank is not fully grounded to the body through the tank straps. Normally I would agree, easier to start at the tank for diagnostic steps, except in this case where the OP describes already having the cluster out and if the fuel gauge was the only issue, not yet established here.
 
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Jimmy01

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Some members may disagree with my advice at this point. Save up your money and buy a new dash and engine harness. This will eliminate anything hidden under the insulation, ( broken, pinched wire) problems that you can't see from the outside. Any burnt, melted wires, connectors etc.... I recommend the ammeter /voltmeter conversion. Other members say that it is just maintenance. I don't know of anyone who does proper electrical maintenance on their cars. The new harnesses will be fresh wires and insulation/connectors. The stock wiring is now 48 years old. The new harnesses from M-H or YearOne are factory replacement type with all factory colored wires and connectors. They are labeled where to go, so no guessing or burned up stuff. The turn signal switch inside of the steering column feeds the power to the turn signals and btake lights. I will send you some electrical links for Mopars. Read them completely and make up your own mind what to do with the info. Electrical systems and grounds especially have always been a weak point on Calssic Mopars. So clean all connections including bulb sockets. Replace all bulbs with new, high quality parts. Wagner, etc... No Asian or Chinese. European are good usually nickel plated to prevent corrosion. Use dielectric greas on all connections. It does a couple of things. #1 it water proofs the connection, #2 it eliminates air contamination of the connection ( read corrosion ) and makes disconnecting any wires much easier in the future since the connections won't corrode stuck.
Always disconnect your battery including the positive side before working on your electrical system, for obvious reasons. A fire extinguisher is good to have on hand for many repairs.
Vintage Chrysler electrical repairs and updates
Vintage Chrysler electrical repairs and updates (part 2)
Improved Wiring for older Mopars
Catalog
https://www.rt-eng.com/rte/images/e/e5/LimiterManualIVR3_D.pdf
http://moparconnectionmagazine.com/...-restoration-turn-signal-switch-installation/
moparleo - would you have any links to companies that sell new dash and harnesses? (1974 Challenger) Thankyou!
 
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