Backup light / 1-4 issue

[Matt B]

One my bumpy road to get my Z road legal there is one last open issue - as far as I can oversee at the moment. My backup lights don't work. Neither does the 1-4 upshift function - which seems to be an advantage but may indicate a "deeper" issue...
Here's my analysis results:

- Connector 237, R/H under dash, blue wire on pin "N": being the power source for B/U and 1-4 it reads 12.8V with ignition on
- Connector 239, R/H under dash, light green wire on pin "D", coming from the B/U switch: the incoming wire should read around 12V with ignition on and reverse gear engage but doesn't. Reading is 0. Outgoing side proves grounded via the backup bulbs as expected.
- To verify that there is no issue around splice S118 (which I couldn't locate) I tested voltage at 1-4 upshift solenoid connector. With ignition on but engine off it reads about 10V green/white wire vs. black wire as well as versus ground. So the dark blue wire routing current into the upshift relay (same as routes current to the backup light switch) must be hot as expected.
- bridging the C237 N and 239 D (and thereby simulating a closed B/U switch) turns on the backup light as it should

So, to me it seems very obvious that the backup light switch has an issue, however I didn't find a way to pull it with the tranny in place.
What concerns me is that the 1-4 upshift is inactive, too though there is voltage applied. I.e. I can shift through all gears with no effort, no matter if the engine is running or not. Coincidence? Both devices defect? Or does it indicate a deeper issue?

Unfortunately the backup light switch is in such a poor position that I don't see a chance to directly analyze its behavior at the pins. And before I try to pull it (which seems awkward) I want to make sure I didn't oversee anything.

[jw63]

This won?t necessarily answer your question but a few thoughts:

Does your car have it?s original/stock chip? Some aftermarket chips disable the 1-4 shift function.

There?s a very good chance your backup switch is just bad. It is possible to remove with the trans in but it?s a pain in the you know what. I was able to get mine out eventually but it probably took 2+ hours. Ended up chopping the connector off first to get a standard socket on it.


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[secondchance]

My thoughts:

* Either aftermarket chip or 1-4 shift was disabled by pulling the plug to solenoid on the side of the transmission. Either way, it?s a good thing.

* most likely back up switch went bad. What gear do you leave the par parked? Recommend 1st gear instead of reverse.

[TX '90 ZR1]

Actually changing the reverse light switch is not that bad with the proper tools.
First you need to get the clutch slave cylinder out of the way. Just get it out of the way. No need to disconnect the fluid line.
Now you can get to the switch. Use an offset 02 sensor socket and a thin swivel head 3/8" ratchet. The longer the ratchet the better.
Pic attached of tools and switches.
Hope this helps. :cheers:
14976

[Matt B]

Thanks for these helpful points. I've immediately ordered a socket as shown on the picture. Wasn't aware these exist but for sure it will make live MUCH easier.
As far as 1-4 is concerned my idea was that someone tried to poorly kill the function by cutting a wire or connection and thereby also hit the backup lights. I'm not keen on that kind of upshift dictatorship either. But reverse lamps are legally required.

As far as parking is concerned I don't know what the previous owner preferred. But it's likely that she spent substantial amounts of time resting in reverse gear. I never use reverse, always 1st (or even neutral as my cars are parked on even ground). But it's good to know that extended reverse gear engagement may damage the switch.

[wfot]

I never leave the trans in gear. I use the brake. I have always heard it puts stress on things that don't need it. IF i were to leave the car in gear, it would be 4th. 4th is not a gear, it is a 1:1 dog that locks the front/rear main shafts together, thus leaving no pressure on any gear sets or the counter shaft, just a thought

John

[Matt B]

Good point. Just remember the issues automatic transmission may have when a car is parked on a steep hill in "P" with no parking brake engaged... This in worst case can lead to a lock out situation so yes, there for sure is a stress on things.
On the other hand - that's what a transmission is made for - but for sure not "P" in an automatic transmission or a backup light switch...

Looking forwards to getting this fixed. I never realized that the ZR has 4 (!!!) backup lights. It's an amazing amount of light it sheds to make backing up safe :)

[ram_g]

Just to reiterate the point that it is certainly possible to replace the backup switch from below without removing anything other than repositioning the clutch slave. And that the OE backup switches do go bad.

[Paul Workman]

My thoughts:

* most likely back up switch went bad. What gear do you leave the par parked? Recommend 1st gear instead of reverse.

Ho! Good ta know. Never thought of that. Neither of our Zs' backup lights work. (Yeah, I know... Raul Julia said it best:)

https://www.youtube.com/watch?v=wTVDpOaTGsc

[WARP TEN]

Ho! Good ta know. Never thought of that. Neither of our Zs' backup lights work. (Yeah, I know... Raul Julia said it best:)

https://www.youtube.com/watch?v=wTVDpOaTGsc

Ha Ha Paul--I loved Raul Julia. Especially in Presumed Innocent as Harrison Ford's lawyer Sandy Stern. He was superb. Too bad we lost him so young, age 54 in 1994.--Bob

[secondchance]

Ho! Good ta know. Never thought of that. Neither of our Zs' backup lights work. (Yeah, I know... Raul Julia said it best:)

https://www.youtube.com/watch?v=wTVDpOaTGsc

Gumball ralley. I think I saw that movie in 1976.:cheers:
I don?t remember why but developed a habit of leaving my manual cars in reverse just in case parking brake didn?t work right. After back up light switch failure, I changed the habit to 1st gear.

[Matt B]

Thanks for the helpful hints how to remove the switch. I pulled mine today within less then 15 minutes. It's the OEM Pollak switch.
I bench testet it and it works very well. It already engages when only 0.08" depressed (about 2mm) and reads around 0.4 ohm resistance. Resistance is stable through the entire travel of the switch.
When plugged to the harness and manually depressed all backup lamps go up. So clearly there are no electrical issues.

Nevertheless, putting the switch back in place, fully seated and with no additional washer, there is no backup lights in reverse gear...
Looks like an issue with engagement of the switch. I checked the shop manual but there seems to be no adjustment to the engagement pin. Also I could not detect any excessive wear.


By the way - happy easter ;)

[secondchance]

Thanks for the helpful hints how to remove the switch. I pulled mine today within less then 15 minutes. It's the OEM Pollak switch.
I bench testet it and it works very well. It already engages when only 0.08" depressed (about 2mm) and reads around 0.4 ohm resistance. Resistance is stable through the entire travel of the switch.
When plugged to the harness and manually depressed all backup lamps go up. So clearly there are no electrical issues.

Nevertheless, putting the switch back in place, fully seated and with no additional washer, there is no backup lights in reverse gear...
Looks like an issue with engagement of the switch. I checked the shop manual but there seems to be no adjustment to the engagement pin. Also I could not detect any excessive wear.


By the way - happy easter ;)

Send an email to Bill and see what he thinks.
billb@zfdoc.com
http://www.zfdoc.com/S6-40ShifterOptions.htm

[Matt B]

Thanks. I dropped him a message.

Today I checked the activation pin together with my mistress, an endoscope and a hex key. Result: moves nicely in and out even when counter-pressure (as much as was possible with a 1/2 ft long hex...) is applied. So, as long as the switch is properly seated (i.e. its tip touches the activation pin) everything should work. But doesnt... Hope Bill has a hint, I'm running out of ideas.

[ram_g]

Interesting. My OEM switch was haphazard when removed and tested - initially it seemed fine and I was in the same boat as you, but then when I played with it some more it quit working. Wonder if that's the same thing going on with yours.

BTW I sourced my replacement from Eckler's. It looked slightly different but screwed in and worked fine. I'm kicking myself that I didn't take a picture of old and new switches side by side.

[DRM500RUBYZR-1]

I trust you checked the bulbs?
If so; Then.
Replace the switch.
:cheers:
Marty

[Matt B]

I checked absolutely EVERYTHING. Manually engaging the switch (when removed from the transmission housing) turns on all lights as desired. So it's a mechanical issue.

My new Ecklers replacement is already on the way. Hope it will fix the issue. Just takes ages to get it here... And it didn't expect my OEM switch to actually work that fine when bench tested.

[Paul Workman]

:happy1:

[Matt B]

:cheers: :)

I meanwhile discovered that the switch pin is too far inside the transmission. Fully extended (with reverse gear engaged) it barely touches the backup light pin.

No answer by Bill so far. I will wait for the Ecklers switch but as long as it's not longer and thereby reaches further into the housing it won't help.
In that case I will squeeze a thin teflon disc between pin and switch to fill the gap. I'm sure that's gonna work BUT would prefer the know the reason. There must be a reason and I hope that no tranny internals are affected...

[ram_g]

:cheers: :)

In that case I will squeeze a thin teflon disc between pin and switch to fill the gap.

Finding it hard to visualize how that disc is going to stay in place, given that the switch contact point is a shiny/slippery ball bearing.

[Matt B]

Well, it's just a tad bit smaller sized than the bore diameter. So there's not much room for it to actually move, no place to go. I hope...

For sure it's better to grind down the mating surface of the switch to get it deeper down the hole. But as long as I don't know where the root cause lies I rather not make any mechanical changes but take a reversible interim solution to gain some time

[DRM500RUBYZR-1]

For over twenty years it has been the switch, as they have routinely failed.
While the possibility exists that it could be more, the probability remains high that it is just the switch.
Let us know what happens once it has been replaced, and if needed, we can go from there.
Best wishes for a simple solution!
:cheers:
Marty

[ram_g]

I agree with Marty, it seems improbable that your transmission has developed a fault that does not appear common, whereas the switch being defective is quite common.

One way of harmonizing both views is to reflect on the fact that we don't really know what the functional specification was in the first place, for how much deflection was needed to activate the switch. Perhaps GM and/or ZF specified a very small deflection to activate the switch, whereas over time the switches become less and less sensitive needing more deflection to activate. So when you're bench testing your switch, you're pressing down enough to activate it, while a new switch would be much more sensitive and capable of switching on the reverse lights with just a tiny input from the transmission. This is all just conjecture, of course, but as I said maybe a way to see how both "facts" would align.

[Matt B]

Hm, very good point. Maybe the required travel is really THAT small... The new switch is on it's way anyway, unfortunately takes ages to arrive here. So for my second attempt to get her certified next week I'll have to go with the interim solution. But as soon as the switch arrives I will try it.
Most probably you are right.

[Matt B]

Wise man! Never thought about that point. And it scares me when I do.

I received a notification that the switch will be delivered tomorrow. Let's pray it will happen as on Wednesday I have my federal inspection and definitely would appreciate to NOT install any work around just for that (no backup light -> no registration). Also then we'll have the answer: German angst or a real mechanical issue :D

[secondchance]

My grandfather (IIRC) said that if left in REVERSE and someone tried steal it by push starting.... Well, never mind about the rest: that makes 'sense'...I guess!:neutral:

Reminds me of local news when I lived in Florida. A guy tried to steal gas from a camper during the night but had the hose in a wrong tank and tried to siphone using his mouth. Quite a surprise.:)

[ram_g]

Reminds me of local news when I lived in Florida. A guy tried to steal gas from a camper during the night but had the hose in a wrong tank and tried to siphone using his mouth. Quite a surprise.:)

I guess, oh sh!t went through his head...

Sorry, multiple puns! :)

[ZR2]

Interesting, I have a 94 and my backup light does not work and I do not have any skip shift functions either, so no matter how I drive I am able to go thru all the gears. Rarely do I have it out at night and even rarer would I use reverse at night, so it hasnt bothered me enough to try and fix it.

[dredgeguy]

We will be changing out my backup light switch this Sunday at our Wazoo maintenance day in Westminster. Come on over.

[ZR2]

A possibility!!!! Pretty close by in Reisterstown. Thanks for reminding me.

[Matt B]

Okay then... New switch arrived perfectly in time for my federal inspection. And your experience was confirmed. It works! That means that these switches use only between 0.04" and 0.08" travel to engage the circuit. Way more precision than I expected, wow. My old one engaged at about 0.08" which apparently already was out of tolerance.
1-4 is still not operating but maybe the selenoid has an issue or was disabled. My initial idea was a relation between both issues as both systems are fed by the same wire. But apparently it was just a coincidence and thankfully I was wrong and it was so easy!!

Thanks for your great support!!!

[ram_g]

Awesome, good to hear!

[aod]

Actually changing the reverse light switch is not that bad with the proper tools.
First you need to get the clutch slave cylinder out of the way. Just get it out of the way. No need to disconnect the fluid line.
Now you can get to the switch. Use an offset 02 sensor socket and a thin swivel head 3/8" ratchet. The longer the ratchet the better.
Pic attached of tools and switches.
Hope this helps. :cheers:
14976


Thanks for posting this. Mine has just failed this year as well. So weird to have multiple failures happening at the same time. And I do not park it in reverse. I have a new switch from Ecklers ordered. I've never moved the slave cylinder before. Is it a PITA to push the plunger back in when you are bolting it back in? Any advice there? Also, once you move the slave cylinder do you have access to disconnect the connector going to the switch before you start removing the switch? Sorry for the dumb questions, I haven't gotten under the car yet to see what I'm getting into, but I understand it isn't a fun process.


Thanks!

[TX '90 ZR1]

Thanks for posting this. Mine has just failed this year as well. So weird to have multiple failures happening at the same time. And I do not park it in reverse. I have a new switch from Ecklers ordered. I've never moved the slave cylinder before. Is it a PITA to push the plunger back in when you are bolting it back in? Any advice there? Also, once you move the slave cylinder do you have access to disconnect the connector going to the switch before you start removing the switch? Sorry for the dumb questions, I haven't gotten under the car yet to see what I'm getting into, but I understand it isn't a fun process.


Thanks!

As always, getting the car up on a lift makes life easier. It is doable without one if necessary.
I have not noticed the slave removal and re-installation to be any different than other hydraulic clutch systems. Just make sure you get it lined up when putting it back in. If your slave has not been changed, check it for signs of leakage. Might as well change it out if it looks suspicious. Unless you are NCRS anal, use a slave from a later year. The position of the bleeder is much more accessible on the later ones as opposed to the '90.
Getting the connector off the original switch can be a bit of a challenge depending on the dexterity of your fingers. The new switch will have a pigtail so will not be an issue to reconnect. Be sure and secure the wiring after installation.
Hope this helps.
I notice you have not joined the registry yet. Not required, but sign up and get a cool T-shirt plus a lot of other benefits!!!
:cheers:

[aod]

As always, getting the car up on a lift makes life easier. It is doable without one if necessary.
I have not noticed the slave removal and re-installation to be any different than other hydraulic clutch systems. Just make sure you get it lined up when putting it back in. If your slave has not been changed, check it for signs of leakage. Might as well change it out if it looks suspicious. Unless you are NCRS anal, use a slave from a later year. The position of the bleeder is much more accessible on the later ones as opposed to the '90.
Getting the connector off the original switch can be a bit of a challenge depending on the dexterity of your fingers. The new switch will have a pigtail so will not be an issue to reconnect. Be sure and secure the wiring after installation.
Hope this helps.
I notice you have not joined the registry yet. Not required, but sign up and get a cool T-shirt plus a lot of other benefits!!!
:cheers:


Thanks for that. I just got a Quickjack so it should make things a bit easier. And thank you for the reminder to join the registry. I've been meaning to but always got sidetracked for whatever reason. I have now joined! :cheers:

[TX '90 ZR1]

Thanks for that. I just got a Quickjack so it should make things a bit easier. And thank you for the reminder to join the registry. I've been meaning to but always got sidetracked for whatever reason. I have now joined! :cheers:

:thumbsup: :cheers:

[aod]

As always, getting the car up on a lift makes life easier. It is doable without one if necessary.
I have not noticed the slave removal and re-installation to be any different than other hydraulic clutch systems. Just make sure you get it lined up when putting it back in. If your slave has not been changed, check it for signs of leakage. Might as well change it out if it looks suspicious. Unless you are NCRS anal, use a slave from a later year. The position of the bleeder is much more accessible on the later ones as opposed to the '90.
Getting the connector off the original switch can be a bit of a challenge depending on the dexterity of your fingers. The new switch will have a pigtail so will not be an issue to reconnect. Be sure and secure the wiring after installation.
Hope this helps.
I notice you have not joined the registry yet. Not required, but sign up and get a cool T-shirt plus a lot of other benefits!!!
:cheers:


So I got the reverse switch replaced and reverse lights work! Unfortunately, I'm guessing I did not get the slave cylinder lined up correctly when I put it back in. The clutch pedal goes to the floor with no resistance. Any tips on how to make sure it is lined up correctly when you put it back together?


Thanks again!

[JG95ZR1]

AOD aim the slave rod to the fork indentation. It?s slightly to the right of center from under neath.The slave will not go all the way in on its own if it is aligned, you will need to push on it from behind about an 1? to hit the bell housing to be able to get the mounting nuts on. At that point you should be on.


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[TX '90 ZR1]

AOD aim the slave rod to the fork indentation. It?s slightly to the right of center from under neath.The slave will not go all the way in on its own if it is aligned, you will need to push on it from behind about an 1? to hit the bell housing to be able to get the mounting nuts on. At that point you should be on.


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This ^^^ :cheers:

[Johnny5]

what socket is it that you ordered. I have to replace mine as I checked my fuses + bulbs. no luck. FYI heibeck tunes the car and rids that annoying skip shift

[TX '90 ZR1]

what socket is it that you ordered. I have to replace mine as I checked my fuses + bulbs. no luck. FYI heibeck tunes the car and rids that annoying skip shift

Johnny,
I used an offset 3/8" drive O2 sensor wrench with a long, flex head, 3/8" ratchet. Works great.
Here's a pic. :cheers:

16985

[Matt B]

Exactly that :)

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