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djkeev
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Joined: September 30, 2007
Posts: 32632
Location: Reading Pennsylvania
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 Posted: Fri May 22, 2015 4:29 am Post subject: Power and Ground for Auxillary Gauges |
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i am installing two extra gauges, a Tachometer and an Oil Pressure Gauge.
Both units are 2" VDO units and will be mounted in Brickwerks Ash tray gauge pod, also sold by T3.
The wiring of each individualgauge I completely understand,
my question is .............
can I utilize the same +12v and -ground wire for both gauges?
Will their operation be affected by sharing these wires?
I plan to power them using the 15amp fuse #16 that supplies the horn only.
It is switched via the ignition and is an item very very very rarely used by me.
It seems like an ideal power supply point for the gauges. If they dip on those rare occassions that I actually must warn someone via the horn....... So be it.
I am hoping the factory harness has the green tach wire in it already and sits unused.... Wishful thinking I know!
Thanks for your feedback...
Dave
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Last edited by djkeev on Fri May 22, 2015 5:55 am; edited 1 time in total |
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VWinVT
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Joined: April 21, 2013
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Location: North East Kingdom
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| Posted: Fri May 22, 2015 4:46 am Post subject: |
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I am interested to see if this will work also. I have a Dakota Digital for my air-cooled lump that is not wired off the ignition switch. This would be a simple solution to get the gauge on switched power.
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1981 Westfalia with a 2001 Cabrio ABA
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Big wheel turns by the grace of God.
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dhaavers
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| Posted: Fri May 22, 2015 5:55 am Post subject: |
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Alistair covered some great options here: http://www.thesamba.com/vw/forum/viewtopic.php?t=511676
- Run directly to fuse block
- G2 is key-on power
- G8 is dimmer-ed illumination
- ground as you wish
- NO IN-LINE SPLICING/TAPPING!
This is my plan for later this summer...
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"The WonderVan"
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thatvwbusguy
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Joined: April 18, 2007
Posts: 1712
Location: Newmarket, New Hampshire
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| Posted: Fri May 22, 2015 6:14 am Post subject: |
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As Dave mentions, on 86-91 vans, you can grab power from the G terminals on the rear of the fuse block. No need to tap into any wires when nice 1/4" tabs are ripe for the picking.
Here is a full listing of the G terminals and their functions as originally posted by tencentlife:
G1 & G3- X-bus load-controlled power (hot when ign. on, goes cold when starter operates) via S12
G2 & G5- #15 ignition-switched power via S18 (this is the ideal power source for extra instruments)
G4- D+ (alternator trigger circuit) via alternator warning LED
G6-dead end
G7 -headlights power
G8 -dimmer-controlled panel lighting power (to light your extra gauges)
G9 -parking lights power via S20
G10- hot when windshield washer pump runs
Ground the gauges to the chassis using a ring terminal and a toothed washer. Scrape away enough paint after you drill the hole for the ring terminal mounting screw to ensure a good ground. A thin coating of dielectric compound over the ground connection once everything is nice and tight will help to fend off oxidation and corrosion as long as possible.
For 80-85 vans, a piggyback connector on the circuit protected (upper) side of any ignition controlled fuse should do the trick. Fuse assignments may change from aircooled to watercooled, so check your owners manual and use your trusty VOM or test light to confirm that you have a switched circuit.
Depending on the options installed, there may even be a couple open male tabs on the fuse block. The Dakota Digital ODYR/ SLX-11-1 gauge is listed as pulling 0.2A. If this is the gauge you have, there is no need to worry about overloading a circuit.
_________________
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'85 Zetec Westfalia
Newmarket, NH
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion. |
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djkeev
Samba Moderator
Joined: September 30, 2007
Posts: 32632
Location: Reading Pennsylvania
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| Posted: Fri May 22, 2015 6:23 am Post subject: |
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| dhaavers wrote: |
Alistair covered some great options here: http://www.thesamba.com/vw/forum/viewtopic.php?t=511676
- Run directly to fuse block
- G2 is key-on power
- G8 is dimmer-ed illumination
- ground as you wish
- NO IN-LINE SPLICING/TAPPING!
This is my plan for later this summer... |
On my 86 (wiring diagram from Vin G 055 690)
G2 is protected by Fuse #18 a 10amp. This fuse serves the Seat Belt warning system and Brake warning system (foot and Parking) fuse Panel terminals G2, G5 and D7 are empty on the same fuse.
Interestingly....... Fuse 6 Terminals C22 and B16 is Vacant.
The Green wire is present in my Cluster Plug T14 spot 9 ........ I highlighted the numbers with a Sharpie......
The Green wire is also present in my engine wire box Plug T7a spot 5 and the green wire exits the box to the coil....... Green wire by my Pinky goes to Coil.....
I will check continuity to verify this but if the tach wire is already run, I will simply clip the green a few inches from the T14 connector (Allowing splice room just in case a Cluster tach is installed some day in the future and to not be THAT PO!!!! ) and pigtail it to my New VDO Tach. Why run a new Tach signal wire that already exists in the factory harness??
So again...... Sharing a common 12v feed and a Common ground will present no problems?
I will power up the electrics and verify the G2 terminal as a switched power point.
My Oil Pressure Gauge is from VanCafe..... An outfit I greatly respect but I do cringe at their instruction to Scotch Lock into an existing power wire to pull switched 12volts ..... I HATE SCOTCH LOCKS!!!!! Let's just design a system to destroy the integrity of good wires! 
Dave
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crazyvwvanman
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Joined: January 28, 2008
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| Posted: Fri May 22, 2015 7:50 am Post subject: |
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In 86-91 vans the green wire is used whether there is a tach or not. The oil pressure warning board in the cluster uses it. When it sees 2000 rpm and higher it monitors the high pressure oil switch. If you cut the green wire only the low pressure switch will be used by the oil warning system.
Mark |
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RocketBox
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Joined: March 20, 2014
Posts: 354
Location: Boise, ID
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| Posted: Fri May 22, 2015 7:59 am Post subject: |
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can i ask which gauges and senders you're using?
I'd like to install an oil pressure and oil temp for starters but get lost with which senders and gauges i need.... i called Oriley's and the said that oil pressure gauges don't need sender units.
_________________
84 Vanagon - tintop, 1.9L wbx. Complete Rebuild done August 2014. 2000~ miles on it so far... SOLD
80 Vanagon Camper ASI Riveria - subaru 2.2 conversion project. 1993 Subary legacy donor car + Riveria = AWESOME! |
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VWinVT
Samba Member
Joined: April 21, 2013
Posts: 1541
Location: North East Kingdom
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| Posted: Fri May 22, 2015 8:07 am Post subject: |
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| thatvwbusguy wrote: |
As Dave mentions, on 86-91 vans, you can grab power from the G terminals on the rear of the fuse block. No need to tap into any wires when nice 1/4" tabs are ripe for the picking.
Here is a full listing of the G terminals and their functions as originally posted by tencentlife:
G1 & G3- X-bus load-controlled power (hot when ign. on, goes cold when starter operates) via S12
G2 & G5- #15 ignition-switched power via S18 (this is the ideal power source for extra instruments)
G4- D+ (alternator trigger circuit) via alternator warning LED
G6-dead end
G7 -headlights power
G8 -dimmer-controlled panel lighting power (to light your extra gauges)
G9 -parking lights power via S20
G10- hot when windshield washer pump runs
Ground the gauges to the chassis using a ring terminal and a toothed washer. Scrape away enough paint after you drill the hole for the ring terminal mounting screw to ensure a good ground. A thin coating of dielectric compound over the ground connection once everything is nice and tight will help to fend off oxidation and corrosion as long as possible.
For 80-85 vans, a piggyback connector on the circuit protected (upper) side of any ignition controlled fuse should do the trick. Fuse assignments may change from aircooled to watercooled, so check your owners manual and use your trusty VOM or test light to confirm that you have a switched circuit.
Depending on the options installed, there may even be a couple open male tabs on the fuse block. The Dakota Digital ODYR/ SLX-11-1 gauge is listed as pulling 0.2A. If this is the gauge you have, there is no need to worry about overloading a circuit.
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Thank you for the pic and info…This makes things a bit easier. Should be a simple fix to locate an upper slot to tie into!
_________________
1981 Westfalia with a 2001 Cabrio ABA
Small wheel turns by the firing rod,
Big wheel turns by the grace of God.
Every time that wheel turns 'round,
You're bound to cover just a little more ground. |
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djkeev
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Joined: September 30, 2007
Posts: 32632
Location: Reading Pennsylvania
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djkeev
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thatvwbusguy
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Joined: April 18, 2007
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Location: Newmarket, New Hampshire
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| Posted: Fri May 22, 2015 10:06 am Post subject: |
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| RocketBox wrote: |
| i called Oriley's and the said that oil pressure gauges don't need sender units. |
Oddly enough, the guys at O'Reilly got this one right (kinda). There are two basic types of oil pressure gauges.
Mechanical oil pressure gauges use an adapter and a tiny tube to pressurize a bulb inside the gauge and move the indicator needle using the actual engine oil pressure (seriously, I wouldn't make something like this up).
Electric oil pressure gauges use a sender that converts the pressure of the oil on the engine side of the sender to an electric signal that is then converted to a pressure reading inside the gauge.
Both types are readily available and they both typically work fine. The mechanical gauge has the potential drawback of spraying oil all over the place if the tube gets damaged or a fitting comes loose. If this happens, be sure to pay attention to the oil pressure gauge, since you could conceivably run the engine dry if you ignored it long enough.
If an electric gauge fails, you won't have the slightest clue what your oil pressure is, but at least the oil should still be in the engine where it belongs.
Grounding both gauges at a common ground point should be fine as long as it is a solid connection. The stock grounding trees are probably not a great choice unless you remove them and clean them up really well before installing the gauges.
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Jay Brown
'85 Zetec Westfalia
Newmarket, NH
If you want others to be happy, practice compassion.
If you want to be happy, practice compassion. |
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RocketBox
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Posts: 354
Location: Boise, ID
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| Posted: Fri May 22, 2015 11:06 am Post subject: |
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ok - thanks Jay! running a mechanical unit up near the dash with a long ass tube on a vanagon seems like a bad idea to me. i'll run the wires rather than a tremendously long oil tube.
_________________
84 Vanagon - tintop, 1.9L wbx. Complete Rebuild done August 2014. 2000~ miles on it so far... SOLD
80 Vanagon Camper ASI Riveria - subaru 2.2 conversion project. 1993 Subary legacy donor car + Riveria = AWESOME! |
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Christopher Schimke
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| Posted: Fri May 22, 2015 11:23 am Post subject: |
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| thatvwbusguy wrote: |
Mechanical oil pressure gauges use an adapter and a tiny tube to pressurize a bulb inside the gauge and move the indicator needle using the actual engine oil pressure (seriously, I wouldn't make something like this up).
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Yeah, that is called a Bourdon tube type gauge and the engineering inside one is incredibly simple, yet super cool at the same time.
When the Bourdon tube (which is a flattened tube that is wound into a C-shape or spiral) inside the gauge is pressurized, it wants to straighten out. Attached to the tube on one end is the pressure inlet, but the other end is usually attached to a linkage, pinion and gear set that actually operates the needle. Like I said, very simple and effective, yet very cool piece of engineering. There are other, more complicated variations of the Bourdon tube gauge, but this is an illustration of the most basic type.
Sorry for the sidetrack. Just thought it would be cool to share that tidbit with anyone who may not know about it.
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kamzcab86
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| Posted: Fri May 22, 2015 11:57 am Post subject: Re: Power and Ground for Auxillary Gauges |
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| djkeev wrote: |
can I utilize the same +12v and -ground wire for both gauges?
Will their operation be affected by sharing these wires? |
FWIW, the Cabriolets have three factory-installed VDO gauges in their center consoles (oil pressure, oil temp, volts... boy, do I miss these when driving the van!). Here is their wiring diagram:
The ground for all three is a spot on one of ground "trees" behind the relay panel. The oil pressure gauge uses a dual-sender (0.3 bar), similar to the one you bought.
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djkeev
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| Posted: Fri May 22, 2015 2:56 pm Post subject: |
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Decisions made!
For the Tach, I Tee'd into the green tach wire at the instrument cluster and ran a Green wire to the VDO "S" terminal.
Ran the provided wire from VanCafe from the Oil Pressure Gauge following the factory harness back to the engine.
For both gauges, I had abandoned the Illuminated Dash Lighter so I pulled the 12v dash lights utilizing the lighter light wire using a Blue wire.
I pulled the Ground for the lights from the lighter Brown Ground Wire using a brown wire.
I pulled Ground (-) for the gauges from the recently cleaned Stars above the fuse panel using a Brown Wire.
For the switched +12v for the gauges I plugged into G2 on the rear of the fuse panel using a Red Wire.
The lights, ground and 12v wires leapfrog from one gauge to the other.
Done deal! No backing out now! 
Dave
_________________
Stop Dead Photo Links how to post photos
Ghia
http://www.thesamba.com/vw/forum/viewtopic.php?t=392473
Vanagon
http://www.thesamba.com/vw/forum/viewtopic.php?p=6315537#6315537
Beetle
https://www.thesamba.com/vw/forum/viewtopic.php?t=482968&highlight=74+super+vert |
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Skidub
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