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.
z031718-5.jpg

[aod]

Originally Posted by 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.
Attachment 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]

Originally Posted by aod

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.
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[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]

Originally Posted by 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

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.

z031718-5.jpg

[Paul Workman]

Originally Posted by secondchance

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]

Originally Posted by Paul Workman

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