Electrical Reverse Light Switch Question

[MJkid67]

This is my second post as I am working through some minor issues on the new to me 1985 CJ7 .

I'm having trouble with getting the reverse lights working. I removed the reverse light switch from the driver's side of the T-5 Transmission and it did not pass the continuity test when I pressed the ball side of the switch in. So, I purchased a new one from Crown, tested it for continuity before I installed it, and after it was installed (about 2 weeks ago) and it had continuity.

So I had some time this past weekend and still couldn't get the reverse lights working. I backtracked and tested the new switch with the transmission in reverse and now I don't have continuity (between the two posts). I tried loosening it a little and then tightening it a bit more than it was with no luck. I then took it out and it tests fine outside of the truck.

I'm stumped! Any ideas or tricks?

Thanks

 

[Sawjaws]

Sounds like maybe it is a NC switch and when you install it, it is making the switch during install and opening. So, if there is something in the installation that is keeping it pressed in, it will stay in that state. Is it doing this no matter what gear it's in?

 

[MJkid67]

Sawjaws, I wasn't aware that NC and a NO switches were available. I know that when the ball is depressed I have continuity across the two posts.

I will check later today if the state changes in other gears. Thanks.

 

[Sawjaws]

Fingers crossed!. I did a little online research last night too and it is possible to have the switch seated too far in as well. Something thing to be conscious of as well. Good luck!

 

[Belizean]

Think I have the NO on my T-176 .

 

[MJkid67]

So I put the Transmission into first gear and checked for continuity and nothing.

I'll experiment with the depth of the switch tomorrow and get back here with the results.

 

[Sawjaws]

So, after re-reading your initial response. It is acting like a NO switch, which seems correct. Sounds like you already tried adjusting depth as well. I'm curious if there is something misaligned with your shift rail. It may well not be an electrical issue.

 

[MJkid67]

Does addressing those issues require removing the Transmission and splitting it open?

This is the new switch that is installed now...

 

[MJkid67]

Now I just reread those instructions. I'll look more closely at the washer thickness on the new switch and report back.

 

[TSB8C]

Yes, this switch is a NO (normally open) switch and pushing the plunger closes the switch/circuit to send power to the backup lights. This switch can also be used as a neutral safety switch, allowing power to the starter only when the tranny is in neutral or park (for auto tranny applications). When installed in the T-5 , the shift rail has a portion that pushes against the plunger to close the switch. If that is not happening, either the switch is not mounted (inserted) into the tranny far enough (due to a washer or spacer on the switch) of the shift rail is worn where it hits the plunger. So obviously test the switch when not installed using a multimeter to check continuity (none when just sitting and continuity when pressing the plunger). If the switch is good, look into the mounting hole on the tranny with a light and watch for the shift rail as the tranny is moved into and out of reverse, checking for excessive wear or not. If that all looks good, adjust the amount of shims (washers) when mounting the switch. If it is not inserted far enough (too much shimming), then the shift rail won't press the plunger enough. If it is not shimmed enough (too few or no washers at all on the switch) then the shift rail will hit too hard, possibly not able to shift into reverse or cause too much wear on the rail due to excessive pressure and rubbing on the switch plunger. My approach has been to shift the tranny into reverse with the switch removed, then start mounting the switch (screwing it in) with the multimeter attached checking continuity as I do that. Then I can tell the exact moment (how far it is screwed in) at the point the multimeter shows it is activated. Based on that distance (how many threads are left that aren't screwed in yet) I can select the correct thickness of shims/washers I need. Just in enough to activate, but not too far in to affect shifting or cause excessive rubbing/wear over time.

 

[Belizean]

Nice write up TSB8C as always. I’ve a question for you. I don’t have a part # for mine on a T-176 . Last time I went to the part store i believe I got an NC and not a NO switch. Is there a description in a part number that designates if it is one or the other ? Or just take my multimeter and test it there ? The counter people had no clue there was a difference.

 

[TSB8C]

The Crown part # for the reverse light switch on a T-176 is J5751207. This is an NO (normally open) switch that operates just like the J8134068 for the T-5 . I don't know of any specific designator in the part # that says whether it's NO or NC. Just different #'s for different parts and you have to get the right one for your application. Some auto Transmission shifter assemblies use a NC switch that opens or disconnects the circuit to prevent juice from going to the starter solenoid when shifted into gear (activates the plunger). That is where an NC switch would work. But for reverse lights, you need an NO that only closes (or connects) when you shift into reverse to send juice to the backup lights. In the CJ harness, the red wire has a switched +12V source (hot with key on) and the white with tracer goes to the backup lights. Here's that T-176 switch installed and the pigtail connector:



When I installed my 700R4 auto tranny, it has neither a reverse light switch nor a neutral safety switch either one. So I had to install both externally. My Lokar shifter assembly has a spot for the neutral safety switch on a bracket near the shifter lever. This is an NO switch that is depressed (closed) by notches on the shifter base when in park or neutral. So by connecting the light blue wire to the starter solenoid through this switch (spliced some extensions to reach), it only allows the starter solenoid to engage when the switch is closed by the shifter lever. I had to use the same install steps outlined above in terms of shimming it so that it gets fully depressed, but doesn't interfere with the operation of the shifter. For the backup lights, another NO switch is mounted on a bracket to two of the pan bolts and the shifter base has a separate "lever" that presses the plunger to turn on the backup lights. There are slotted holes in this bracket to adjust the positioning of the switch so that the lever only hits it when in the reverse position.

Reverse light switch and bracket:

Neutral safety switch:

 

[Belizean]

Great explanation ! Thanks.

 

[MJkid67]

Thanks for suggesting that process TSB8C.

I was able to confirm that the shift rail is present when the Transmission is in Reverse.

The rail is not present while not in Reverse.

However, with the switch fully seated, I suspect that the ball is not being depressed enough. It seems like the shaft needs to go into the transmission another 1/8" or so.

Is there a switch that is at least 1/8" longer? Could I get a used OEM or a switch from a different model that might be longer?

Perhaps there is just a little too much slop in there because of age?

 

[TSB8C]

It does seem you may have excessive wear on the shift rail if the switch is inserted as far as possible (no washers or shims) and the rail is still not pressing the ball/plunger enough to activate it. Proper fix is to replace/adjust the rail inside the tranny. Work-around as you suggested is look for another switch that is a slight bit taller and could screw in further. In terms of another switch that is longer, I do not know the specific dimensions of this switch. So hard to search for another that would be the same diameter and threads, but slightly taller. The WVE #1S5283 looks close. I don't know if the threads are the same, and you'd have to replace the pigtail connector, but the GM #14069600 might alo be another option.

Another potential option is to file or ground down a bit off the face of the "nut" part of the switch on the side where it screws in. Then it could screw in further before bottoming out.

Cut or grind away this part so it screws in further. Since you're not torquing this thing to some high amount, you just need to leave enough for a box wrench or 6-point socket to grab it. Maybe you could pick up the additional 1/8th inch you need.

 

[Jeep Soup]

Just for Schmidt and Giggles,
Stick a Phillips screw driver tip into the hole, have a sharpie ready, have a Sexy and Beautiful Volunteer shift it in and out of reverse and "Feel" how much the screw driver moves. Then do it again and mark the screw driver for the In and out positions.
Compare to your switch.

AND???
Did the reverse lights WORK before?
Do you have a Neutral Safety Switch on this Transmission ?
Pull it out. Check IT'S size. Put it in the Reverse hole and see if it works.
Go get another Neutral safely switch.
Feex't

 

[MJkid67]

Laughing at that post Jeep Soup!

Didn't know that there was a neutral safety switch. I'll look and report back.

 

[MJkid67]

Update (for those that care):

I cut down the face of the nut, but that was such an imperfect process that it weakened the extended shaft and it snapped off while I was carefully tightening it. Not sure if it's possible to do this successfully with a dremel tool.

So I found a Ford/Volvo switch that has a longer shaft (not sure about the thread diameter) on eBay. It was only $9.95, so it's worth a shot.

And, today, I found an OEM switch NOS (still in sealed factory bag) on eBay. I'm hoping that the Crown switch is not made to the same spec as OEM. I know that the Crown pinion seal is not the same size as OEM.

 

[Jeep Soup]

Evidently there is not a Neutral Safety Switch for you to check out for size. Most went to a Clutch Pedal Safe Switch.
Some had a 4-5th gear switch for the ECM unit.

Good luck, I was wondering how things were going?

 

[MJkid67]

Correct, there is no neutral safety switch.