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Wiring Harness for 70 Road Runner

G

Gospel Runner

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I cannot believe these harnesses cost over $600. That is highway robbery. On top of that it seems like what is for sale is only one third of what is needed. I have what looks like three rectangular boxes plugged into my bulkhead, from which wires are protruding. The picture of the wiring harnesses I have seen all show one rectangular box and a bunch of wires neatly coiled up. I assume I will have to pay separately for the other two? My question is, are there no other options other then these high priced wiring harnesses, and what are you actually getting when you buy them? Is everything included, just not shown in the pictures? If you have gone down this path before, please enlighten me. Another side question, are the cheaper, less expensive harnesses worth looking at or are they just junk? I hope I did not ask too many questions at one time. Thanks in advance for your help in this matter.
 
Supply & demand, welcome to Mopar economics. Yep, what you see is correct on the bulkhead. Which harness do you need ? I personally would only recommend M&H Year One, or Evans for any harness.
 
The harness in my engine compartment is a mess. I have a battery drain that I cannot find. I have to disconnect my battery or it will be dead the next day. It is a brand new battery. I need an electrician to tell me where to start looking. I don't know if the aftermarket alternator is putting out enough voltage to handle all of the electrical needs I have added. (Elec. water pump, fuel pump, vacuum pump, trans. brake, ignition and various gauges)
 
Gospel Runner said:
The harness in my engine compartment is a mess. I have a battery drain that I cannot find. I have to disconnect my battery or it will be dead the next day. It is a brand new battery. I need an electrician to tell me where to start looking. I don't know if the aftermarket alternator is putting out enough voltage to handle all of the electrical needs I have added. (Elec. water pump, fuel pump, vacuum pump, trans. brake, ignition and various gauges)
Click to expand...

Hey Gospel, it's a slow process, but you can find your own bad wire. If you have a good electric meter (one where power can flow through it) you can unhook the + side of the battery and hook the meter between the + battery terminal & the + battery cable. Take a good look at your wiring harness & un-plug the circuits (one at a time & replace them as you go). When your battery drain on the meter drops to near "Zero", then you've found the circuit with the problem.

You could even have a drain inside the starter, the starter relay, maybe even the ignition switch itself. I don't think there's too many circuits to check. "Maybe" you even have an issue with the wiring going to one of your electric add-on accessories?
 
Alternator diode shorted, trunk/underhood light staying on, glove box light, dome light? Just a thought.
 
Here's a picture of the bulkhead wiring in place.

IMG_1065.JPG
 
Purple beeper my battery is in the trunk, can I pick up the positive lead off the starter? I want to definitely change the engine harness. Can you buy just that specific harness? Is it cheaper to buy just one harness?
 
I know the wiring is expensive, but the M&H stuff fits perfect. I replaced ALL the wiring in my 70 Road Runner because I did not want to risk putting tons of time and money into restoring it only to have electrical gremlins, or even worse, a bad fire. IMHO, the wiring is cheap insurance.

Just my two cents worth...

Hawk
 
Gospel Runner said:
Purple beeper my battery is in the trunk, can I pick up the positive lead off the starter? I want to definitely change the engine harness. Can you buy just that specific harness? Is it cheaper to buy just one harness?
Click to expand...
Yes, you can purchase one harness at a time. Engine harnesses will run about $100 - $150. The more pricey harness is the dash harness. Usually around $400 - $500.
 
I have to save up, but I am going to bite the bullet and get the new wiring harness. Thank you gentlemen!
 
Purple Beeper while I am waiting to save up for the new harness I am going to use your method to track down the voltage leak. Thank you sir! Have a great day!
 
Gospel Runner said:
The harness in my engine compartment is a mess. I have a battery drain that I cannot find. I have to disconnect my battery or it will be dead the next day. It is a brand new battery. I need an electrician to tell me where to start looking. I don't know if the aftermarket alternator is putting out enough voltage to handle all of the electrical needs I have added. (Elec. water pump, fuel pump, vacuum pump, trans. brake, ignition and various gauges)
Click to expand...
PurpleBeeper has the correct method, but I'll add a few tips. If the parasitic draw is over 50mA, get a cheap test lamp at O'Rielly. Place the lamp in series with the battery, and unplug fuses one at a time until the test lamp no longer glows. You have found the branch of the problem. Now reconnect the battery, and place the test lamp across the fuse you found that had the parasitic draw. With a wiring diagram, start to unplug what is on that circuit until the lamp goes out. Now you have located the draw. This method would also work with a ammeter. If using an ammeter, an analog version would work better so you can see the changes at a distance.

Long story short, I was chasing a parasitic draw on a friends C4 Corvette. It was several hundred mA and the test lamp was bright. A tail lamp socket had a soft short, but here is the weird part of the story. An ohm meter measured no shorts in the socket whatsoever with, or without a bulb, yet when DC was applied the socket sinked current!

Moral of the story is to keep an open mind when troubleshooting. As the late, great Robert A Pease would say; "The first step in (analog) troubleshooting is to have an open mind that anything can be the cause."
 
Last edited:
Thank you for your additional wisdom. I will let you know how I fair. Have a great day!
 
Today I placed the multi-meter dial on 10A and attached one terminal on the disconnected end of the battery terminal and the other end on the actual terminal. The multi-meter read .05A which is negligible. That reading led me to believe there was no real draw. Even with that I continued to check each fuse and I got no change in the reading. I need someone to tell me if I did this wrong or if there is another way to check the draw? Thank you!
 
You may want to check a lower range to be certain, but I agree 50mA is negligible. You could have an intermittent draw, but not likely.
 
A drain years ago on mine turned out to be the TicTocTach. I use a battery cut off switch and would not know if there is a minor draw overnight. Just for good measure, carefully remove all three banks on the bulkhead connector and spray heavily with electrical contact cleaner until it runs out clear. Gently reinstall.
 
When I tried setting the multi-meter to other settings the display went to 1 or it showed 0.
 
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