Reverse Lights Not Working

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1974DartSport

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Mandeville, Louisiana
Some of you may remember the difficulty I had getting my 74 Dart started after restoring it. I finally broke down and took it to a mechanic who kept it two weeks and finally got it running. Prior to taking it to him, the reverse lights worked. After bringing it home, the reverse lights do not work.

I just learned that the mechanic changed the neutral safety switch when he had my car. The Dart is an automatic transmission, column shift and the old neutral safety switch was the original from 1974 when I bought the car.

Q. 1 - Could the new switch be the reason the reverse lights do not work?
Q. 2 - How would I test to find the problem? I have a multimeter.

All bulbs in the brake lights and reverse lights are new. Brake lights, turn signals, and flashers work fine.
 
Maybe if yuo look under the car the wires to the neutral are lose. I think that is the only switch that runs the reverse lights.
 
I am guessing your mechanic installed the wrong neutral safety switch which also is supposed to have a switch for the reverse lights. Also, check to see that the connector at the switch on the transmission is pushed on all the way and check fuses.
 
Okay, the switch is the three prong thingamajig that plugs into the transmission. What my mechanic changed was the "plastic prong" that has three wires coming from the engine wiring harness. The old plastic prong was the original from 1974 when I bought the car, and it kept falling off the switch that correctly in the transmission. However, the old plastic prong worked properly prior to replacement (when connected the backup lights worked).

I have been to several parts stores. They can find the switch that plugs into the transmission, but they don't find the "plastic prong". What is the correct name for this prong, and could it be the wrong item for my new switch?

Are they readily available?
 
Randy, still having problems, huh?
Your '74 Dart's neutral safety switch has three "prongs". A prong is the short metal male terminal sticking out of the switch that makes contact with the female terminal on the end of a wire, completing the electrical circuit. What I call the "connector" is the round plastic fitting that is molded around the three female terminals, and it plugs "onto" (rather than "into") the three exposed male terminals ("prongs") on the switch - it basically is held in place by the action of the female terminals gripping the male terminals. I'm not certain if the plastic connector is designed to have a lip molded around its inner circumference that "snaps" into a groove around the switch's outer circumference, holding them together (or vice versa) - I haven't inspected both of them closely.

Since I never replaced one, I can't say for certain, but I believe the neutral safety switch is "threaded", rather than "plugged", into the transmission housing. It really does nothing more than act as a ground for the switch. With the gear selector in "Park" or "Neutral" the switch circuit is closed and allows the engine to start. If the gear selector is in any other position other than "P" or "N", the circuit is open and the engine can't start.

Obviously, this only pertains to the "start" circuit. Once the engine is running, you can change to any gear position you choose and the switch has no effect. It's called a "safety" switch for the obvious reason - the car won't start while in gear to prevent it from causing damage or injury.

The other two outer terminals of the switch are where the circuit is closed when the gear selector is in the "Reverse" position. In any other position, the circuit is open and... no backup lights. Again, the ground is made to the transmission housing.

Theoretically, if all of the wires are solid with no breaks and have no bare spots rubbing to cause a short, all of the wire and connector terminals are clean and make good, tight connections, all of the bulbs are confirmed to be good with tight sockets and clean terminals, then I can't see how the neutral safety switch or its associated "connector" can be your problem.

Since I haven't seen what goes on inside the transmission to make all of this magic happen, I can't say what might be a possible issue in there. If a lever, pawl, tang, tab, prong, tine, or whatever you might call it is malfunctioning in there, sorry, I can't help.

Keep us posted,
Jerry
 
Had same problem on my 72. Check and make sure the plug is on the right way, mine was plugged in the wrong way, changed it and "walla" back-up lights.
 
I think what he means is that it doesn't matter which way you push the connector on, it is simply completing the circuit from one side to the other. The gear selector in "R" position closes the circuit in the neutral safety (reverse) switch. That's why someone earlier suggested that you can by-pass the switch completely by crossing over the connector from one female terminal to the other (on the wire harness). If you get backup lights, then the switch (or gizmo inside transmission) is faulty.
 
I crawled under the car tonight and noticed the connector was the original connector that has been on the car since 1974 and was the same connector on it prior to taking it to the mechanic. I pulled it off the neutral safety switch and immediately noticed the switch was different. So I grabbed the detailed invoice from the mechanic and there was a charge on the bill for a new neutral safety switch. Prior to taking it to the mechanic, I replugged that connector so many times, I was really beginning to think about gluing the damn thing on, so it wouldn't fall off again.

As suggested above, I took a paper clip, unbent it, and put each end in the outer two ends of the three prong female connector. I turned the ignition to ON, and put the car in reverse. The backup lights came on! So obviously my problem must be the new neutral switch is bad or the wrong one for my car.

I think I'll visit Advance Auto tomorrow. Did they make different kinds of switches for 74 Darts? If I remove the faulty switch, will transmission fluid leak out?
 
Randy,
This is what it says in my Torqueflite A-727 (similar) Transmission Handbook:

"To replace the switch, begin by placing a container under the transmission. Remove the switch; have an assistant move the gearshift lever to the "Park" and "Neutral" positions. Make sure that the arm on the valve body is intact and centered in the hole. It is fairly common for the plastic wiper on the detent arm to become loose or break. The detent plate itself can become loose from repeated abuse. Either of these conditions can cause problems with neutral safety switch operation. Replace the gasket and thread the switch back into the case, tighten to 24 ft-lbs. Refill the transmission as required."

"To test the switch for neutral safety function, remove the wiring connector and check for continuity between the center terminal and the case in the "Park" and "Neutral" positions only. Be sure to confirm the gearshift adjustment prior to condemning the switch."

In other words, the switch could still be correct and functioning, but the gearshift selector or detent arm could be out of adjustment.

Keep us posted,
Jerry
 
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