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P-Bear
Samba Member
Joined: July 20, 2020
Posts: 147
Location: Portland OR
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 Posted: Tue Nov 10, 2020 3:13 pm Post subject: Alarm wiring re:door switch/dome light |
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Quick question about finishing up an alarm system I am wiring.
The door switches are ground switches correct? Meaning the dome light always has power but it's not grounded so when the door is opened it completes the circuit by supplying the ground right?
Please refrain from stating the reasons to not have an alarm. I've read all of those responses and it's too late for that.
Thanks.
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1974 Super Beetle |
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Tim Donahoe
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Joined: December 08, 2012
Posts: 11740
Location: Redding, CA
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| Posted: Tue Nov 10, 2020 3:18 pm Post subject: Re: Alarm wiring re:door switch/dome light |
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Right.
Tim
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P-Bear
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Joined: July 20, 2020
Posts: 147
Location: Portland OR
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| Posted: Tue Nov 10, 2020 3:19 pm Post subject: Re: Alarm wiring re:door switch/dome light |
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Thanks Tim.
I can finish this thing up now.
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ashman40
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Joined: February 16, 2007
Posts: 15982
Location: North Florida, USA
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| Posted: Tue Nov 10, 2020 8:43 pm Post subject: Re: Alarm wiring re:door switch/dome light |
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| P-Bear wrote: |
| The door switches are ground switches correct? Meaning the dome light always has power but it's not grounded so when the door is opened it completes the circuit by supplying the ground right? |
I'm gonna say, "sometimes".
If you have the simple door switches that have a single male spade terminal...
... then "yes", when the door is opened the switch grounds the wire connected to the terminal to the body via the screw that holds the switch in place.
But if you have the OE 4-prong type door switch like this...
... shown on the left side door of this '70/'71 wiring diagram (F2):
EDIT: I believe from the way it is wired the brown wires in the pic short together when the door is opened. Since one of these is grounded, it grounds the dome light wire to turn it ON.
But the other two wire terminals short together on door open to allow the grey "SU" wire from the ignition switch to only ground the (H5) door buzzer when the key is inserted in the ignition. If the door switch wires were all grounded every time the door opened then the buzzer would sound every time the door was opened. Instead the buzzer is meant to remind you not to forget your keys when you open the door with the keys still in the ignition.
These 4-prong switches were not grounded at the switch body like the single prong ones. These were pass thru (DPST) switches. The did work the same for the dome switch because the pass thru allowed the dome light wires to pass thru to a grounded wire (brown), not because the switch itself grounded the wire.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road  }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}
Last edited by ashman40 on Wed Nov 11, 2020 3:42 pm; edited 1 time in total |
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Tim Donahoe
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Joined: December 08, 2012
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Location: Redding, CA
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| Posted: Tue Nov 10, 2020 9:06 pm Post subject: Re: Alarm wiring re:door switch/dome light |
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Ash, he has a 1974 Super Beetle. I’ve replaced the switches in my ‘74 Super Neerle, and they had two terminals.
Tim
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ashman40
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Joined: February 16, 2007
Posts: 15982
Location: North Florida, USA
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| Posted: Wed Nov 11, 2020 10:17 am Post subject: Re: Alarm wiring re:door switch/dome light |
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| Tim Donahoe wrote: |
| Ash, he has a 1974 Super Beetle. I’ve replaced the switches in my ‘74 Super Neerle, and they had two terminals. |
Thanks Tim. I missed that the OP had a '74 SB. 
I was just trying to highlight that not all door switches ground their wires.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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P-Bear
Samba Member
Joined: July 20, 2020
Posts: 147
Location: Portland OR
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| Posted: Wed Nov 11, 2020 11:51 am Post subject: Re: Alarm wiring re:door switch/dome light |
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Ash, it's my fault you didn't know the vehicle I had. I'm bad at not stating it, assuming people would look at my signature.
Sorry for that, but at least you provided great info for those that have a 4 prong switch.
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cmyoch
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Joined: June 16, 2017
Posts: 61
Location: Smithton, IL
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| Posted: Wed Nov 11, 2020 6:19 pm Post subject: Re: Alarm wiring re:door switch/dome light |
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I am following this thread. My dome light did not work when I first acquired my 74 SB. One day, the light started working only when the passenger door was opened, not the driver's side door. Then, everything stopped again. I pulled the switches from the doors and sanded the connections hoping that would work...it didn't. I plan on tracing all the wiring through the system to get it fully operational, including the buzzer if it is still in the car.
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1974 Super Beetle (First ever VW owned)
Jack of all trades. Master of none! |
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ashman40
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Joined: February 16, 2007
Posts: 15982
Location: North Florida, USA
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| Posted: Wed Nov 11, 2020 10:21 pm Post subject: Re: Alarm wiring re:door switch/dome light |
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| cmyoch wrote: |
| I am following this thread. My dome light did not work when I first acquired my 74 SB. One day, the light started working only when the passenger door was opened... |
First thing to check is the fuse that powers the dome light.
Then check that the dome light bulb still works.
Then check that there is constant 12v at the dome light itself?
Then check that the brown wire coming from the door switches to the dome light is grounded when either door is open?
Cleaning up all the wire terminals is also something to look at.
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AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!} |
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P-Bear
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Joined: July 20, 2020
Posts: 147
Location: Portland OR
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| Posted: Thu Nov 12, 2020 10:32 am Post subject: Re: Alarm wiring re:door switch/dome light |
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Thanks again Tim. My keyless entry and alarm work perfect now.
As far as the dome light working...mine worked intermittently when I first purchased my car. I replaced the switches and it still wouldn't work.
I ended up taking some 220 grit sandpaper and cleaned up the bulb contacts in the housing and its worked every time going on 6 months now. So yes, as Ash said. Clean all the contacts.
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