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

[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]

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