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74 cali
Samba Member
Joined: August 07, 2013
Posts: 98
Location: Oregon
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 Posted: Mon Nov 11, 2013 12:25 pm Post subject: Another wiring question |
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I was looking at another thread on wiring and someone had this picture of the back of their speedo and it showed power to the wire labeled #15. I couldn't really find a reference to this specifically on the wiring charts I was using to my my 74 std and assumed it must be a ground. Any charts that reference what this is and what should be connected to it? I also don't remember what circuit #15 is.
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1970VWGUY
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Joined: September 15, 2013
Posts: 864
Location: Natrona Heights, PA
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| Posted: Mon Nov 11, 2013 12:34 pm Post subject: |
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| On mine 70 and on your wiring diagram that wire connects to the fuse closest to the drivers side looking from the trunk....The bottom half of the fuse box with several other wires. |
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SBD
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Joined: October 24, 2012
Posts: 3298
Location: SOUTH DAKOTA
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| Posted: Mon Nov 11, 2013 2:15 pm Post subject: |
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| I believe that wire sends power to those 3 bulbs. They are then lit by grounding through their individual senders/circuits. |
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Aussiebug
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Joined: June 03, 2002
Posts: 2162
Location: Adelaide Australia
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| Posted: Mon Nov 11, 2013 2:54 pm Post subject: |
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SBD is right. That wire brings 12v to the joint can holder strip behind the speedo, with the ignition on. The individual wires from those bulbs (oil, blinker and gen/alt) then go to their respective components to complete the circuit for that light. You'll see that the connector strip is insulated from the speedo housing so it can take the 12v + without shorting.
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Rob
Rob and Dave's aircooled VW pages
Repairs and maintenance for the home mechanic
http://www.vw-resource.com |
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ashman40
Samba Member
Joined: February 16, 2007
Posts: 16759
Location: North Florida, USA
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| Posted: Mon Nov 11, 2013 5:05 pm Post subject: Re: Another wiring question |
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| 74 cali wrote: |
| I was looking at another thread on wiring and someone had this picture of the back of their speedo and it showed power to the wire labeled #15. I couldn't really find a reference to this specifically on the wiring charts I was using to my my 74 std and assumed it must be a ground. Any charts that reference what this is and what should be connected to it? I also don't remember what circuit #15 is. |
Starting with the '73-later wiring diagram
Look at the top of column 34. You will see a black wire coming from fuse #12. It goes down to J6 (fuel level gauge) before going to the K2, K3 and K5 indicator lamps. While it is difficult to see it with two of the indicator lamps K3 clearly goes to the oil pressure switch and then grounds at the bottom of the diagram.
If you prefer the earlier diagrams
Look at the speedo near the middle of the diagram. The three indicators are on the right side. Note the thin black line connecting all three. This turns to a thick black wire that goes to the fuel gauge and then on to the fuse box.
You can tell these three bulbs area not grounded when you compare them with the other lamps in the speedo. The other lamps all have a line ending with a large black dot on the circumference of the speedo indicating they ground to the speedo case. Follow the brown wire (which also starts from a black dot on the speedo circumference) up to where it grounds at the sideways "T". The three indicator lamps do not ground to the case, nor do they have a common ground.
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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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74 cali
Samba Member
Joined: August 07, 2013
Posts: 98
Location: Oregon
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| Posted: Wed Nov 13, 2013 10:41 am Post subject: |
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| That bottom wiring diagram is the one I used to wire the car. I guess I assumed that the black wire coming from the fuel vibrator was connected to K2 or the gen light. So all I need to do is take that black wire off k2 and put it on that tab that is at the bottom of the speedo (#15 ign on)? Also the brown wire that comes from the fuel sending unit is grounded to the speedo case? |
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mrbigmax
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Joined: September 10, 2011
Posts: 1289
Location: Modesto, CA
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| Posted: Thu Nov 14, 2013 1:15 am Post subject: |
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| 74 cali wrote: |
| That bottom wiring diagram is the one I used to wire the car. I guess I assumed that the black wire coming from the fuel vibrator was connected to K2 or the gen light. So all I need to do is take that black wire off k2 and put it on that tab that is at the bottom of the speedo (#15 ign on)? Also the brown wire that comes from the fuel sending unit is grounded to the speedo case? |
1st question - Yes, the fuel gauge gets 12v from the same place the warning lights get their 12v. The 3 warning lamps share a 12v and ground their respective circuits, oil pressure switch, voltage regulator and turn signal relay. The almost no voltage reading at the lamps is good with everything off.
These lamps are wired +12v --> warning lamp --> switch --> ground. (BTW the interior light is wired this way too)
The rest of the lights +12 --> switch --> light (headlight, etc.) --> ground.
Just remember #15(black) is +12v w/ ignition on, #30(red) is +12v always hot, #31(brown) is the ground.
2nd question - Yes, the brown sending unit wire gets grounded on the speedo but for the ground to work, the speedo needs to ground through the mounting ears. |
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74 cali
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Joined: August 07, 2013
Posts: 98
Location: Oregon
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| Posted: Thu Nov 14, 2013 8:21 am Post subject: |
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| Thanks. I'll switch the wire off of the oil light to the common power for the 3 switches. |
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mrbigmax
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Joined: September 10, 2011
Posts: 1289
Location: Modesto, CA
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| Posted: Thu Nov 14, 2013 9:06 pm Post subject: |
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The photo you posted shows the proper placement of the wires for the warning lamps. Here's a drawing of the correct wire placement (ignore the colors in this drawing.)
To better see the indicator light socket for the 3 bulbs, here's another photo. As you can see, the +12v is shared with the 3 warning lamp sockets through to the lamp holder' body isolating the 3 bulbs from the grounded speedometer body.
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