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dkthom7
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Joined: April 02, 2008
Posts: 23
Location: Atlanta, GA
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 Posted: Sun Feb 21, 2010 8:21 pm Post subject: Fuel guage vibrator question |
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Can someone tell me what is the purpose of the vibrator that is attached to the back of the fuel guage?
The reason I am asking is because I am planning to install Porsche 914 gauges in my '69 beetle. I have tested the 914 fuel gauge and it seems to work without the VW vibrator but I don't want to damage something by leaving it out if I need it. Thanks. |
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Glenn 
Mr. 010
Joined: December 25, 2001
Posts: 79493
Location: Sneaking up behind you
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| Posted: Sun Feb 21, 2010 8:23 pm Post subject: |
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It evens out the voltage so the gauge doesn't swing side to side when you make turns.
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Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
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dkthom7
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Joined: April 02, 2008
Posts: 23
Location: Atlanta, GA
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| Posted: Sun Feb 21, 2010 8:29 pm Post subject: |
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| Glen, does that mean that I should figure out a way to wire the vibrator to the porsche fuel gauge? The porsche fuel gauge doesn't seem to have one unless it's internal. |
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Glenn
Mr. 010
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| Posted: Sun Feb 21, 2010 8:30 pm Post subject: |
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I don't know.
I also don't know if the stock VW sender will give accurate reading for the 914 gauge.
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Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
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Luftgekült
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Joined: December 30, 2007
Posts: 388
Location: Canary Islands, Spain
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| Posted: Mon Feb 22, 2010 12:19 am Post subject: |
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I thought the purpose of the vibrator was to provide always the same voltage to the fuel gauge, so it reads the same when, for example, you turn the lights on. I really don't think it has nothing to do with the needle moving on corners. It is only my opion, and I am not an expert.
I am using 914 gauges without vibrator. The fuel gauge is not very accurate, it reads 3/4 when full. It takes 300km to reach the 1/2 mark and only 100km from the 1/2 to zero.
I also have a 911 oil temp/press gauge. When I turn the lights on, oil temp rise and press drop a little. I haven't seen any changes in the fuel gauge, though.
I believe the stock vibrator could make my oil readings stable.
My question is, is there any kind of morden electronics (diodes or whatever) that could replace the vibrator?
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'71 VW 1302 1300cc in progress....
'72 VW 1302S 2109cc
'84 Passat Variant GL 1.6TD |
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Denis
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Joined: October 05, 2005
Posts: 19
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| Posted: Mon Feb 22, 2010 6:16 am Post subject: Voltage Regulator |
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The vibrator is a mechanical voltage regulator. Not sure about VW's but the Mustang I have has a vibrator which lowers the battery voltage from 12 volts to 5 volts for the gauges.
There are electronic voltage regulators whcih do the same thing. They can be purchased at any good electronics store. About the size of a transistor. |
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gevmage
Samba Member
Joined: February 12, 2008
Posts: 1066
Location: Kentucky
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| Posted: Mon Feb 22, 2010 1:33 pm Post subject: Re: Fuel guage vibrator question |
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| dkthom7 wrote: |
Can someone tell me what is the purpose of the vibrator that is attached to the back of the fuel guage?
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As someone else has said, it's an electro-mechanical device to stabilize the AVERAGE voltage sent to the fuel gauge. That way, your fuel level doesn't vary between when you're running on battery (as low as 11.5V) and running on the generator (as high as 15V).
I don't know what the effective average voltage is; it might be 5V.
The best answer to your question is to use a gauge and a sender that are designed to work together, and wire them up how they're supposed to be wired up.
If you want to use the Porche gauge with the VW sender, then you'll have to figure out the voltage expected by the gauge and what its upper and lower current limits are, and wire things up so that it matches and won't pull too much current.
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Craig Steffen
Getting my 1972 Super back on the road
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Luftgekült
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Location: Canary Islands, Spain
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| Posted: Mon Feb 22, 2010 2:18 pm Post subject: |
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The vibrator output is 12v
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'71 VW 1302 1300cc in progress....
'72 VW 1302S 2109cc
'84 Passat Variant GL 1.6TD |
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gevmage
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Joined: February 12, 2008
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Location: Kentucky
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| Posted: Mon Feb 22, 2010 2:32 pm Post subject: |
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| Luftgekült wrote: |
| The vibrator output is 12v |
But not the AVERAGE output. It outputs whatever voltage is input, but only about one third the time. So the average effective output is in the range of 4 to 5 volts. I just don't happen to know, and I haven't measured it.
_________________
Craig Steffen
Getting my 1972 Super back on the road
Chronicling it on YT
(channel name "figuring stuff out dot net")
Physicist, pilot, computer person
craigsteffen.net |
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Luftgekült
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Joined: December 30, 2007
Posts: 388
Location: Canary Islands, Spain
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| Posted: Tue Feb 23, 2010 12:46 am Post subject: |
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| gevmage wrote: |
| Luftgekült wrote: |
| The vibrator output is 12v |
But not the AVERAGE output. It outputs whatever voltage is input, but only about one third the time. So the average effective output is in the range of 4 to 5 volts. I just don't happen to know, and I haven't measured it. |
You're right
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'71 VW 1302 1300cc in progress....
'72 VW 1302S 2109cc
'84 Passat Variant GL 1.6TD |
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Rowroy
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| Posted: Tue Feb 23, 2010 6:22 am Post subject: |
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It's quite easy to replace the vibrator with a solid state 5 volt regulator. They only cost about $1.50 at Radio Shack.
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yol
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Joined: July 30, 2007
Posts: 115
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| Posted: Tue Feb 23, 2010 9:08 am Post subject: |
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Like previous post, The vibrator is an elctromechanical voltage regulator - the fuel gauge works on 5 volts.
so, like others mentioned, it is there to reduce the ~12V to 5V by means of duty cycling the 12v ( intermittant on/off) .
it is also true that it is possible to replace it to a solid state 5v regulator.
notice that if you hook the fuel gauge or the fuel sender to 12v you might burn them. both of them are quite sensitive so be careful. |
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dkthom7
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Joined: April 02, 2008
Posts: 23
Location: Atlanta, GA
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| Posted: Tue Mar 23, 2010 8:29 pm Post subject: |
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| FYI - I installed the 914 fuel gauge with the vibrator and the needle would dance between empty and full so I decided to run it without the vibrator. Also, it does not appear to be accurate but it is better than nothing. |
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