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12 V Conversion Voltage Dropping Device (VDD)

Your old Chris-Craft electrical system can be a challenge. If it runs on "juice" pose your questions and offer your advice here.

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beancounter
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12 V Conversion Voltage Dropping Device (VDD)

Post by beancounter » Fri Aug 14, 2015 2:37 pm

An article in the Brass Bell(Summer 2006) discusses wiring regarding the original 6V guages. It describes how to install a Runtz VDD for the guages that are connected to the original 6V sending units. However, the article goes on and describes using a Zenor Diode VDD for applications that have a 12 V sending unit, as in my case as I ordered a new gas tank from Raco Marine (Florida). My question is, does anyone know where I can find a Zenor Diode as described in the article? The transistorized Runtz VDD are readily available, but I am having difficulty locating a Zenor Diode VDD. Thanx, Pete [email protected]

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evansjw44
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Re: 12 V Conversion Voltage Dropping Device (VDD)

Post by evansjw44 » Tue Aug 18, 2015 8:39 am

Let's see if I read this right. You have a 6 volt system and you want to incorporate a fuel gauge and sensor that are 12 volt. You are looking for a zener diode to make the conversion.

You need a voltage boosting device to convert the 6 volt power to 12 volts to power the fuel gauge. A zener diode is a voltage dropping device, not a voltage boosting device. As an electrical/electronics engineer I can envision a device to do what you need but I don't recall ever seeing one. You need to do some research or better yet go on the hunt for a 6 volt fuel tank sensor and gauge.

Fuel tank sensors have a fairly standard flange layout. If you search for car restoration parts (vintage cars) you should be able to find a 6 volt sensor. Look at the fuel tank suppliers too. Try an Ebay search on "fuel tank". Also try a Google search on "fuel tank - vintage". I've seen what you're looking for there.
Jim Evans

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Re: 12 V Conversion Voltage Dropping Device (VDD)

Post by sproat3 » Sat Aug 22, 2015 3:12 pm

This may help, maybe not.
Fuel level sender units are variable resistors attached to floats or magnetic reed switches. They'll work with either 6 or 12 volts DC. The key is to be able to calibrate the sender unit with your gauge.
In my case, I replaced the old original sender unit with a new Moeller stainless steel magnetic reed switch sender with a resistance of 33-240 ohms which is standard. (Check out their website and call their tech support. They're very helpful.)To calibrate it with my original Chris Craft 1960 Capri fuel gauge, I installed a small electronic module under the dash between the sender and the gauge. The module is the Fuel Gauge Wizard I found on eBay. It took about 20 minutes to calibrate (before you put the sending unit in the tank). It works very well and I'm getting accurate fuel level readings on the gauge. (Need to get the anti-slosh option). It needs 12VDC as a power source , but it doesn't care if your gauge was originally on a 6 or 12 VDC system.
Ward Sproat
1960 Chris Craft Capri (Tahoe Heidi)

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bobbystone
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Re: 12 V Conversion Voltage Dropping Device (VDD)

Post by bobbystone » Fri Dec 25, 2015 11:43 am

If you want to go from 6 to 12 volts you can use a device called a boost converter. They're very efficient and you can find loads on eBay. Just make sure you get one with the required amperage.
1958 48' Constellation
Twin 454's with Paragon Transmissions
Hull No. : X-48-107

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