Revers Lights Flickering, Lord Have Mercy

The_Red_Baron

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Hello everybody,

Recently, I was driving with my buddies behind me on the highway, and when we pulled into the apartment parking lot, they said my reverse lights were flickering on and off. "we thought you were telling us to slingshot around you" (watched Fast 9, so of course a bit of Dom was in all of us that night). We tried to get them to do it in the parking lot, to no avail. I just assumed they were yanking my chain, because I wasn't shifting at all on the highway (50-70mph zones, the engine would self destruct in 2nd gear at those speeds). I just put it at the back of my mind, and assumed nothing of it.

Today, at the end of my shift, I noticed that, surprise surprise, my reverse lights were indeed flickering on and off intermittently. I pulled the car around to a clean white brick wall, and tried to get them to react more predictably. So, When shifting up from 1st to 2nd and then to drive, the reverse lights flash on and off once. So, 1st to 2nd, flash, 2nd to drive, flash. Then I tried shifting from drive to neutral, and it wasn't as predictable. Then I thought, "what the hell, might as well see if I can get them to do it in drive alone." Sure enough, they were going crazy. As I jiggled the shifter in drive, the lights would come on and go off, random time differences, and sometimes they would stay on. While extra light coming from the rear of a classic car is a good thing (helps stay visible to distracted drivers), I'd prefer it if I didn't scare people on the highway, making them think I just dropped the car into race mode and I'm about to leave a trans fluid trail like you've never seen.

Anyways, normally I'd have a video to better show what I'm talking about isn't total BS, but my phone died mid shift and I didn't have a charger.

Is there any switch in the column that could be shorting, or just going bad? As far as I know, there really isn't, I thought it was just a rod that goes out to the shift linkages for the trans. Has anyone ever experienced this before?

Side note, I put LEDs (totally legal and meant for street applications btw) all around the car (front turn signals, marker lights, tail lights). I doubt that has anything to do with it. The turn signal switch on the fuse box doesn't interfere with that at all right? I had to put in a digital switch as oppose to a mechanical, seeing as the LED's pull far less voltage and wouldn't make the element inside a mechanical switch hot enough to click like it needs to.

Thanks for any and all input you guys and gals can provide, this forum has been nothing but a gold mine for me...

Red Baron
 

Aspen500

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You have either a neutral safety switch, which also controls the b/u lights, going bad with where it's grounding the circuit when it shouldn't or the wire from the b/u lights has a sporadic short to ground between the lights and neutral switch on the transmission. The wire is violet from the lights to the connector in the left kick panel and after the 9-way connector, it becomes violet with black stripe. The neutral switch closes the ground circuit to turn the b/u lights on.
 

69-

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IIRC - the + supply for the b/u lights go thru the nss at the trans, i'd not assume a short in the b/u wires. The b/u lights are grounded at their bulb base. Otherwise, there would be a need for two long wires from/to the b/u lights, and no OEM is/was prone to such excessive wiring.

I strongly guess its the nss at the trans. It's easy to change (Although some trans oil will give you hugs when you pull it out). Although lately, I had aftermarket nss which did not have perfect sizes... But they are cheap, if one does not work as expected, use a different Brand. This applies to the three wire nss.
 

shadango

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IIRC - the + supply for the b/u lights go thru the nss at the trans, i'd not assume a short in the b/u wires. The b/u lights are grounded at their bulb base. Otherwise, there would be a need for two long wires from/to the b/u lights, and no OEM is/was prone to such excessive wiring.

I strongly guess its the nss at the trans. It's easy to change (Although some trans oil will give you hugs when you pull it out). Although lately, I had aftermarket nss which did not have perfect sizes... But they are cheap, if one does not work as expected, use a different Brand. This applies to the three wire nss.
I was going to suggest the NSS too....and I echo the issue with aftermarket NSSs.....I had tried one in my Cuda smallblock 7272 trans and while it fit fine it did not trigger the lights at all...so my guess is it was too short.....

I ended up finding an aftermarket one at Carlisle a couple years ago that I only recently got around to changing to try an chase a leak.....it works fine....not sure I solved the leak though.....could be the shifter rod seal above it....but I digress.

The brand is "automotive transmission" or maybe "AA Transmission" at 317 831 3066 part#nss 12410cn "70-up aftermarket 3 prong NSS"

Not sure it would be the same part number for the 904 or not?
 

The_Red_Baron

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Thanks guys, I appreciate the responses. I'll most likely grab a NSS and replace it on a day coming up.
 

Aspen500

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I also had an aftermarket switch in my car and it didn't activate the back up lights either. Then I replaced it with a different one (aftermarket) and it worked fine,,,,,,,,,,,for a while (like 2 months). One day, fortunately in my own driveway, it wouldn't crank but the b/u lights still worked, lol. I bypassed the switch and the car started, to get it back in the garage. That evening I was over visiting my dad and mentioned it while we were talking cars (as always). He said there was a jar with 4 or 5 old original Mopar ones on the shelf in the basement and I was welcome to as many as I wanted. That was over 5 years ago and it's still working perfect. Aftermarket,,,,,,,,,,China strikes again.

One thing I never did, for some reason, is check and see if they're still available new from Chrysler yet.
 

Mikes5thAve

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I haven't had problem with the aftermarket ones but make sure they plug in and the right one and work before you put it in.
The plugs look the same but the plug for one with a long hex body usually won't connect to one with a short hex body. That's the only problem I've run into.
 

BudW

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If it is the switch, try to find a NOS or a used part if possible. The repops (ie: China) are not that good.

They make a short 3-wire and a long 3-wire NSS (Neutral Safety Switch). They will both fully interchange (if from a rear wheel/four wheel drive vehicle).
Long NSS.jpg

Short NSS.jpg

The top one came out in '68 (I think) and was superceded with the lower one during the FMJ years. My '77 has the long version and my '86, the Short one.
The lower one was used well into the '90's

Note: I will caution to anyone who hears me. Be very careful removing, moving, transporting, or installing a Chrysler transmission - because that switch (the NSS) is very easy to damage. Wait, scratch that, is EXTREMELY EASY to damage and is/are most likely thing I see is that switch damaged after some like of work around it, or transportation of a transmission (even accidentally kicking a transmission well hidden under the work bench . . .). I even got to the point of removing the NSS before removing a transmission (taping it to the tailhousing) and the last thing to install after an install.
I can also say that I have damaged my share of 'em, as well.

Also make note of the direction of the seal. Both versions above are using the proper usage of the seal.
BudW


Edit: there is also a version that looks close to the short NSS - but for the front wheel drive cars. I have heard the 3-wire electrical connector will not plug in correctly on some of them.
 
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Mikes5thAve

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My 84 and 88 both have the long one, my 79 had short. The plugs didn't interchange. I found that out when the switch on my 88 failed and I tried to use the short one from the 79.
It's strange, some parts sites show the short one for newer cars, others show the long one. Some say they interchange right thru the 70s and 80s others have a cut off..
 
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BudW

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What few memory cells I have left, is thinking the switch change was '79 or '80 - but don't quote me on that.

I do know many of the FWD versions looks like the short version, and screws into the case - but has connector fitment issues.
 

Aspen500

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My 84 and 88 both have the long one, my 79 had short. The plugs didn't interchange. I found that out when the switch on my 88 failed and I tried to use the short one from the 79.
It's strange, some parts sites show the short one for newer cars, others show the long one. Some say they interchange right thru the 70s and 80s others have a cut off..

You can't always trust the parts listings to be accurate. They're only as good as the data the person who entered it all had in front of them. Now, throw in a mid model year change and all bets are off! "Funny" part is, 9 times out of 10 if the listing is wrong at (for example) Advance Auto Parts, it'll be wrong the same way at Napa, O'Reilly, Auto Zone, Carquest........................
 

Mikes5thAve

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I guess simply put make sure the one going in looks the same as what came out and buy local so that return is easy if it doesn't work or plug in.
 
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