Pelican Parts Forums

Pelican Parts Forums (http://forums.pelicanparts.com/)
-   Porsche 911 Technical Forum (http://forums.pelicanparts.com/porsche-911-technical-forum/)
-   -   911 - Reverse light - voltage? (http://forums.pelicanparts.com/porsche-911-technical-forum/1053508-911-reverse-light-voltage.html)

OneMore 02-24-2020 02:13 PM

911 - Reverse light - voltage?
 
Hi,

I’m trying to figure out the reverse light. It hasn’t been working for a while. When I started troubleshooting, the old wires coming out of the transmission going to the back lights got cut.

I connected the leads to the tester, but didn’t see any voltage at the transmission outlet.

Shouldn’t I be reading 12 VDC when shifting to reverse gear?

https://uploads.tapatalk-cdn.com/202...632c3874e3.jpg

https://uploads.tapatalk-cdn.com/202...bb7fc47727.jpg

https://uploads.tapatalk-cdn.com/202...f375f99369.jpg


Sent from my iPhone using Tapatalk

HarryD 02-24-2020 02:22 PM

If both leads are cut, there is no power to the switch. Use your OHM meter to determine if the contacts are closed when in reverse and open when in any other gear.

The green/brown wire goes to the bulb. If the bulb is in place and intact, you should get continuity from the wire to any ground on the car.

The other wire supplies 12v power to the switch when the ignition is in the run position.

OneMore 02-24-2020 03:54 PM

911 - Reverse light - voltage?
 
Thanks for your suggestion .

Regardless of the gear, no change in resistance :(

Any other idea?

https://uploads.tapatalk-cdn.com/202...d08ab7891a.jpg


Sent from my iPhone using Tapatalk

HarryD 02-24-2020 04:58 PM

Is there continuity between the brown/green wire and ground with a bulb in the reverse light holders? if you apply battery power to this wire, do the reverse lights illuminate?

Is there power in the other wire when the key is in the run position?

HarryD 02-24-2020 06:30 PM

Are you sure it is in reverse?

OneMore 02-29-2020 02:27 PM

911 - Reverse light - voltage?
 
Quote:

Originally Posted by HarryD (Post 10763331)
Are you sure it is in reverse?



Sorry for not replying before.
It was in reverse because the wheels were moving in that direction.

I removed the switch in order to figure out how it works. When you press an inner pin the circuit closes. Releasing the pin and the circuit is opened. I checked with the OHM meter as suggested.

Here is where my stupidity reached a new record. In order to avoid a false / weak connection I decided to install it back, torquing the switch with all my energy. Of course, the 33 years old switch couldn’t hold it and got broken; half of the switch is in the transmission outlet and the other half in my hand.
I know.... I should have listened my wife and play with my kiddo instead of being creative...

So, considering the ample space to work underneath.... any suggestions on how to remove the half switch remaining in the transmision ?


https://uploads.tapatalk-cdn.com/202...6fe8a49455.jpghttps://uploads.tapatalk-cdn.com/202...e8b18e0cbd.jpg


Sent from my iPhone using Tapatalk

HarryD 02-29-2020 04:11 PM

Sorry for the trouble.

Can you jam an easy-out into the hole and turn it out?

Use a chisel and try to CAREFULLY turn the remaining piece.

Depending on your confidence in welding, you may be able a weld a nut to it and use that to pull it out.

OneMore 03-02-2020 02:48 AM

It came out!!!.

New part ordered. I’ll follow up once I receive it.

Thanks for the advive


Sent from my iPhone using Tapatalk

r lane 03-02-2020 05:29 AM

This may have been suggested, but is the switch actuating pin intact and in place?

HarryD 03-02-2020 06:27 AM

Quote:

Originally Posted by OneMore (Post 10769609)
It came out!!!.

New part ordered. I’ll follow up once I receive it.

Thanks for the advive


Sent from my iPhone using Tapatalk

Great news. For the record. How did you get it out.

timmy2 03-02-2020 08:12 AM

When checking for voltage are you connecting to the wires on the harness or the switch?
(Looks like the switch in your photo) you can only test for ohms to see if the switch closes with wires disconnected.

The switch will never have voltage without the 2 wires coming from the rear of the engine harness connected to the switch.
One wire of the pair should always have power when ignition is in the run position.

Here is how it works:
One wire comes from the front fuse panel. (power on it with ignition on) It runs directly to the 14 pin connector on the rear fuse panel. The pins for the circuit are 5 and 6.

That same wire on the engine harness side of the 14 pin connector then runs directly to the switch. When the switch closes, the second wire of the pair now has power and it goes back to the 14 pin connector on a different pin. From the second pin in the circuit power goes to the 2 reverse lights.

OneMore 03-02-2020 11:49 AM

Quote:

Originally Posted by r lane (Post 10769702)
This may have been suggested, but is the switch actuating pin intact and in place?



Sorry r lane, I don’t quite follow your question.


Sent from my iPad using Tapatalk

OneMore 03-02-2020 11:50 AM

Quote:

Originally Posted by HarryD (Post 10769755)
Great news. For the record. How did you get it out.



Easy out and chivel.


Sent from my iPad using Tapatalk

OneMore 03-02-2020 11:51 AM

Quote:

Originally Posted by timmy2 (Post 10769851)
When checking for voltage are you connecting to the wires on the harness or the switch?
(Looks like the switch in your photo) you can only test for ohms to see if the switch closes with wires disconnected.

The switch will never have voltage without the 2 wires coming from the rear of the engine harness connected to the switch.
One wire of the pair should always have power when ignition is in the run position.

Here is how it works:
One wire comes from the front fuse panel. (power on it with ignition on) It runs directly to the 14 pin connector on the rear fuse panel. The pins for the circuit are 5 and 6.

That same wire on the engine harness side of the 14 pin connector then runs directly to the switch. When the switch closes, the second wire of the pair now has power and it goes back to the 14 pin connector on a different pin. From the second pin in the circuit power goes to the 2 reverse lights.



That’s correct. The proper way to test the switch is checking resistance, not voltage.




Sent from my iPad using Tapatalk

r lane 03-02-2020 12:59 PM

There is a metal pen or plunger, a couple of mm in diam and approx. 40mm long with a stepdown at the end. Fits into gallery between the switch and the reverse gear fork. When the fork moves in one direction or another, it either pushes or releases the pen and engages or disengages the switch allowing current to flow or shunting it. Actually found that missing in a customers Had I guess been missing sense the transmission had been repaired

OneMore 03-08-2020 04:51 PM

You’re right. I had to shave it a little bit on the edge because it was getting stuck in the switch.


Sent from my iPad using Tapatalk

OneMore 03-08-2020 04:53 PM

911 - Reverse light - voltage?
 
I finally finished this project today. As suspected, the issue was the old switch.

Below a few pics showing the process.

Thanks guys for your feedback!

https://uploads.tapatalk-cdn.com/202...6b4e1c5d91.jpghttps://uploads.tapatalk-cdn.com/202...383ff91e2f.jpghttps://uploads.tapatalk-cdn.com/202...fe80583cc9.jpghttps://uploads.tapatalk-cdn.com/202...a49b17c647.jpghttps://uploads.tapatalk-cdn.com/202...526aaea61e.jpghttps://uploads.tapatalk-cdn.com/202...e7bff66d93.jpg


Sent from my iPad using Tapatalk


All times are GMT -8. The time now is 03:27 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website


DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.