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Dumb reverse lights....

Posted By: sharpie

Dumb reverse lights.... - 06/03/09 06:53 AM

Okay, so weird problem - my reverse lights are on in reverse AND in drive, 2, and 1. Neutral and park do not have them on as usual. I know this must be an issue with the Back Up Light Switch Circuit, but I have no idea how to fix it. Is this common? Do I have a short, or do I just need to change something? Any help is appreciated!
Posted By: Hrtbkr

Re: Dumb reverse lights.... - 06/03/09 11:30 AM

I just worked through this problem. If you have (I"m not sure of the exact year for the change) a '70 or older transmission, the switch in the side is only for neutral safety. The reverse lights are switched either at the floor or column shifter. The trans switch for the older style had a single connector. You can install a newer three prong switch, but then you get the symptoms you describe.
To fix this, you need two friends like I have. Darryl GAVE me the correct valve body (the cam on the shifter rod activates the safety and back up lights plus you get part throttle kick down), and you need Kenny to install it. Automatics are a complete mystery to me , but Kenny swapped VB's last night like it was nothing...
Posted By: scratchnfotraction

Re: Dumb reverse lights.... - 06/03/09 12:38 PM

yes if it on the colum at the floor you need the one wire nss

like said the rooster comb is diff for the 3 prong nss

you can move the rev light switch for some adjustment on the colum some..that might help

the trans you took out would have the nss and correct vb,but I know you said it gone

so its just a matter of the right nss maybe

find out if its got the rev light switch on the colum

Posted By: sharpie

Re: Dumb reverse lights.... - 06/03/09 02:36 PM

Well, my trans is from a 76 truck and my car's a 71, so I think it's supposed to have the 3-wire NSS (same plug came with my wiring harness originally). I don't know if that helps or not.
Posted By: 68HemiB

Re: Dumb reverse lights.... - 06/03/09 03:32 PM

Indeed, the rooster comb inside can vary, but I am not sure that this should come into play, given the years of the parts you used. IIRC, '68 was the last year of the single pin NSS and reverse lights from elsewhere.

It would be very useful diagnostic information if you could establish that the switch and comb are or are not truly the source of your problem. Doing so might avert the need to start digging into the internals of the transmission needlessly.

I would suggest that you disconnect the harness plug from the switch, and use an ohm meter to establish if the outer two pins in fact have continuity in reverse/drive/2/1 and no continuity in park and neutral (matching your symptoms).

a. If this is the case, it's bad news and time to dig further into the switch integrity and switch/comb interaction.

b. However, if the outer pins behave as they should (continuity in reverse, and no other gear), you can breathe a sigh of relief and continue your search external to the transmission itself.
Posted By: 6packattk

Re: Dumb reverse lights.... - 06/03/09 04:35 PM

I ran into this problem on my bee a few years ago and finally figured out my three prong wiring harness plug was so heat hardened it was not plugging in correctly,got one from mopar junk yard,same problem,no one made new ones at the time.Wired each wire to prongs seperately using typical wire crimp connector(tube type)crimped just enough on prong end to make tight like won`t never fall off.Works great,I was getting ready for texas car inspection.Back up lights are checked.Would of liked to have factory end but was not to bee
Posted By: sharpie

Re: Dumb reverse lights.... - 06/03/09 05:01 PM

Does it matter which way the plug goes on? It can only go on two ways, but if upside down won't work, I should know.
Posted By: stumpy

Re: Dumb reverse lights.... - 06/03/09 05:07 PM

It will work either way. The two outer terminals are just in and out not directional.
Posted By: John_Kunkel

Re: Dumb reverse lights.... - 06/03/09 07:37 PM

The only way to know if the transmission is configured correctly for the 3-prong switch is to remove the switch and determine what type of internal lever (roostercomb) is installed. If the lever has two metal contacts it won't operate the 3-prong switch' if it has the correct lever with a plastic shoe the ploastic end might be broken off.

Below is a pic of the different internal levers and the switches that they operate.

Attached picture 5270469-NSSwitches.jpg
Posted By: sharpie

Re: Dumb reverse lights.... - 06/03/09 07:55 PM

Wow John, that's a great picture. I do know that I have the middle lever, with the fox-ears on the switch-side of the lever. I can't tell whether the middle switch is a three-prong, but the one I have in there looks exactly like this:

Posted By: stumpy

Re: Dumb reverse lights.... - 06/03/09 08:55 PM

If you have the middle lever you need a single terminal switch. For backup lights you need the third lever and three prong switch. You can see how the lever slides along the switch to make it work in different positions. The middle one only works the switch with the two points in park and neutral for starting.
Posted By: sharpie

Re: Dumb reverse lights.... - 06/03/09 09:33 PM

So how would I go about resolving the issue?
Posted By: scratchnfotraction

Re: Dumb reverse lights.... - 06/03/09 09:48 PM

pull the vb and install the new 3 prong nss rooster comb in you vb

I have the right rooster comb if ya need it

the vb is for parts so I dont need it

its yours if ya want it



Posted By: John_Kunkel

Re: Dumb reverse lights.... - 06/03/09 10:35 PM

Only the '69 and '70 roostercomb (on the left below) can be used to convert a '68 and earlier valve body, the '71 and later is different.

Attached picture 5270810-Roostercombsandplates.jpg
Posted By: scratchnfotraction

Re: Dumb reverse lights.... - 06/04/09 01:27 AM

maybe not

I thought it was a 76 truck tranny

Posted By: stumpy

Re: Dumb reverse lights.... - 06/04/09 02:34 AM

Seems to me if it was a 76 trans it wouldn't have the two prong lever in it.
Posted By: 68HemiB

Re: Dumb reverse lights.... - 06/04/09 02:39 AM

Referring back to my earlier post...


...it's easier to yank the valve body of a transmission than to hold the probes of an ohm meter up to two pins on the NSS?
Posted By: sharpie

Re: Dumb reverse lights.... - 06/04/09 05:29 AM

I am thinking it's pretty solid that I have the wrong NSS switch in there, because I've seen the inside of the transmission (and thus the shift lever) when I was reconditioning it. Since the only real difference between 69+ NSS is 1- or 3-pin and thus the part that touches the switch (rooster comb seems to be the same), I really think it's the switch. How would I go about re-routing the reverse light circuit? It seems easier to get a 1-pin NSS switch and reroute the reverse light circuit than to replace the shift lever and valve body.
Posted By: scratchnfotraction

Re: Dumb reverse lights.... - 06/04/09 12:09 PM

IMO the rooster comb is easier to do than rewire the rev light circit

the detent ball is the hardest thing to deal with changing it

its 12 or so bolt that hold the vb in place

and you can put a new throttle valve shaft seal in there while your at it

Posted By: 68HemiB

Re: Dumb reverse lights.... - 06/04/09 02:56 PM

Quote:

I am thinking it's pretty solid that I have the wrong NSS switch in there, because I've seen the inside of the transmission (and thus the shift lever) when I was reconditioning it. Since the only real difference between 69+ NSS is 1- or 3-pin and thus the part that touches the switch (rooster comb seems to be the same), I really think it's the switch. How would I go about re-routing the reverse light circuit? It seems easier to get a 1-pin NSS switch and reroute the reverse light circuit than to replace the shift lever and valve body.



Some members (myself included) are a bit confused how such a late transmission could have an early roostercomb. You know more about the ancestry of the transmission, have seen the innards for yourself, and seem to buy onto the "wrong comb" theory, even without testing with an ohm meter. So be it.

Assuming that your problem is a comb/NSS mismatch (as I said - a leap for some of us), the task at hand is to match the NSS and car wiring to the comb, or the comb to the NSS and car wiring. I think I join the majority here in thinking that the latter is the easier path. Your idea to search out a single pin switch leaves you needing a whole 'nother set-up to get your reverse lights working. In a column-shifted automatic, this was done with a switch near the bottom of the steering column. And it is not just a switch and some wires - there needs to be a matching pin-like thing on the shifter linkage to engage the switch. The sarcastic side of me wants to recommend you seek out a "1968 Demon" to gather your needed parts...

I would urge you to confirm your problem first. THEN, if it really is a comb/switch mismatch, reconsider going the comb changing route.
Posted By: sharpie

Re: Dumb reverse lights.... - 06/04/09 03:29 PM

I guess I'll try the ohmmeter. But if there is continuity in D-2-1, what would make it have no continuity in P-N? The only thing that could make this happen is the wrong rooster-comb, is it not?
Posted By: 68HemiB

Re: Dumb reverse lights.... - 06/04/09 03:40 PM

Old, cracked, ATF-soaked connectors with tired oval contacts (remember your question about that?) have been known to do funny things. The center pin is supposed to get GROUNDED when working properly, and do it in Park and Neutral (see the synchronicity there?).

It's not a percentage bet, but it is an easy test to pull out the ohm meter. I could have gotten in my car and driven up there and tested it myself in the time I spent typing out that you should take out your ohm meter.

Okay, maybe that was a slight exaggeration...
Posted By: sharpie

Re: Dumb reverse lights.... - 06/04/09 03:53 PM

Since I don't have an ohmmeter, will a digital multi-meter work?
Posted By: 68HemiB

Re: Dumb reverse lights.... - 06/04/09 04:30 PM

Quote:

Since I don't have an ohmmeter, will a digital multi-meter work?



Doesn't your multi-meter include a setting with the greek letter Omega on it? That would be resistance (measured in ohms). Most do.

If not, all you need to do is confirm when there is or isn't continuity. A wire hooked to a 12 volt source and a test light would work just as well. If you use this method, remember that the CENTER PIN will be grounded (i.e. a DEAD SHORT) in certain gears. Do NOT touch your 12 volt source to the center pin, or any other ground. EVER. Power one outside pin (doesn't matter which one) with 12 volts. In each gear, test the other outside pin with the test light. When it lights - you have continuity. No light = open circuit.

Alternate alternate testing method. Read no further if you get confused, and stick with the stuff above. If you want to remove the risk of a dead short from clipping around with a 12 volt source, do the test backwards, with the 12 volt source hooked into the test light, and the other outboard pin clipped instead to ground. Wherever the probe lights, you have a ground. As above, test for continuity in each gear.

But I bet your multi-meter has a resistance setting...
Posted By: sharpie

Re: Dumb reverse lights.... - 06/04/09 04:51 PM

Yeah, it has a K(Omega) setting.

So I want to get this right so I don't screw it up. Does this look like the right way to check? The one labelled 'Mine' should look like this?

Posted By: 68HemiB

Re: Dumb reverse lights.... - 06/04/09 04:58 PM

Great picture.

Completely wrong interpretation of my words.

In each gear, you are testing for continuity the NSS switch outer pin pair while bolted into the transmission and disconnected from the harness, with the ignition key having nothing to do with it.

Attached picture 5272398-nss_sharpie.JPG
Posted By: sharpie

Re: Dumb reverse lights.... - 06/04/09 06:01 PM

I sort of get it, but I guess I'm not understanding continuity. I thought continuity meant it would make a circuit. If there's no energization from a source (car battery via harness), how would I see continuity? Maybe I don't understand the multi-meter. I know, I am hopeless
Posted By: hooziewhatsit

Re: Dumb reverse lights.... - 06/04/09 06:26 PM

Quote:

I sort of get it, but I guess I'm not understanding continuity. I thought continuity meant it would make a circuit. If there's no energization from a source (car battery via harness), how would I see continuity? Maybe I don't understand the multi-meter. I know, I am hopeless



When you put your multimeter on resistance (omega), it measures resistance. It doesn't need any outside power. To see this, just touch the two probes together. Resistance on the meter should go to 0 ohms.

Now, touch the probes to the two outer pins, and have someone go through each gear. When you see 0 ohms, you have continuity between the pins, just like when you touched the probes together.

This is the 'safest' method as you're not jumping any 12v points to it.


---Alternate method-----

You only need power from an outside source if you want to use a test light. If you want to use this method, put 12v on the left pin. Ground your test light, and touch its probe to the right pin. When the light comes on, there is continuity between the pins.

-Dave
Posted By: 68HemiB

Re: Dumb reverse lights.... - 06/04/09 06:28 PM

Continuity (conductivity) and resistance are opposite sides of the same coin. Yes, you need some sort of "juice" to prove a circuit. That is provided by the battery in your multi-meter.

You use the ohm meter mode of your multi-meter to check for resistance (or LACK of resistance):

High resistance (big number) = open circuit.
Low number (theoretically ZERO) = intact circuit.
Posted By: John_Kunkel

Re: Dumb reverse lights.... - 06/04/09 07:25 PM

Anytime the metal pin in the center of the switch is allowed to extend, the BU light circuit will have continuity; when the correct roostercomb is in place the pin will only extend when the "divot" in the plastic shoe is in line, in all other gears the plastic shoe keeps the pin pushed in (see pic below).

The test results you posted are typical for the wrong 2-eared roostercomb or a correct one with the end of the shoe broken off.

Attached picture 5272637-Switchnshoe.jpg
Posted By: 68HemiB

Re: Dumb reverse lights.... - 06/08/09 04:41 PM





You alluded to a solution in a bacon thread on the General Board.

Care to offer some closure here?
Posted By: sharpie

Re: Dumb reverse lights.... - 06/08/09 05:00 PM

You don't want to know and I don't want to get yelled at for doing something that probably isn't the safest thing in the world...
Posted By: 68HemiB

Re: Dumb reverse lights.... - 06/08/09 05:03 PM

You think you're the first one to carry around an eight year-old in the trunk who jumps out with a flashlight every time you back up?

Posted By: sharpie

Re: Dumb reverse lights.... - 06/08/09 05:08 PM

Quote:

You think you're the first one to carry around an eight year-old in the trunk who jumps out with a flashlight every time you back up?







No, since I wasn't heading into reverse in the forseeable future (I park on the street in between two driveways), and the NSS itself works fine, I just unplugged the reverse lamps. I know, not the best thing to do, but the only thing that wouldn't take a lot of effort but would make it legal to keep shaking down the drivetrain.
Posted By: scratchnfotraction

Re: Dumb reverse lights.... - 06/08/09 05:12 PM

ROTFLMAO

I thought I was the only one that cut the center wire and grounded it to the frame

then run a toggle switch up on the dash to turn back ups on

I figured it took care of shifting before cranking,just cranking on the fly

and the switch gets the tail gaters off the bumper when I throw the white light on them

ya want that rooster comb I gots?? you can have it itss already R&R from the vb

lmk

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