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1stpop
Joined: 03 Dec 2007
Posts: 109
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 Posted: Mon Jun 16, 2008 2:05 pm Post subject: how do I reduce the voltage for my fuel gauge? |
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| I've just finished converting my Ford 103E 'pop' from 6 to 12 volts - everything has gone really well but I'm not sure how to convert the fuel gauge? I got a voltage reducer from my parts guy and he said to just put in on the main feed from the ignition switch. I've tried this and also putting it on the feed from the tank but it just sends the needle straight round to full!!!! The gauge has a live feed from the ignition and a live feed from the tank sender unit. the earth is picked up from the body of the gauge. Anyone got any ideas? |
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peter scott
Joined: 18 Dec 2007
Posts: 7215
Location: Edinburgh
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ukdave2002
Joined: 23 Nov 2007
Posts: 4236
Location: South Cheshire
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| Posted: Thu Jun 19, 2008 4:07 pm Post subject: |
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Hi
The reason your gauge has a live feed and a feed from the tank sender is to compensate for voltage fluctuations (otherwise the fuel gauge would wander as the battery charged and loads like headlamps were switched on).
If you put a regulator just on the live side , the gauge will always read double what it should, if you put it on the sender side it will try and regulate to a fixed voltage , until the voltage drops below certain level and then it will just become unstable.
So you can use one of the regulators that Peter posted but it must supply both the live feed to the gauge and the “input” to the sender, that should then work fine, and it’s a cheap solution.
Dave |
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Uncle Joe
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| Posted: Thu Jun 19, 2008 4:53 pm Post subject: |
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| Uk, just a thought, but on my Chrysler, the fuel gauge uses a 5v supply. This used to be done by a Flintstone-era regulator, which was unreliable to say the least. I made up an elctronic version using a 7805 chip, heat sink, and capacitor. Could a modified version of this set up not be used? It certainly was cheap and fun to do, as it improved my lack of electrical knowledge a bit. Now its roughly wartime Lucas....ie, quite a lot of blackouts! |
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pigtin
Joined: 23 Nov 2007
Posts: 1879
Location: Herne Bay
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| Posted: Thu Jun 19, 2008 5:11 pm Post subject: |
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Possibly easier using a zener diode and resistor? or I may be over-simplifying not knowing details of the unit.  |
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Uncle Joe
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| Posted: Thu Jun 19, 2008 5:19 pm Post subject: |
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Remember the Zener diodes on the old 12v Triumph motorcycles? I still have nightmares!  |
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pigtin
Joined: 23 Nov 2007
Posts: 1879
Location: Herne Bay
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| Posted: Thu Jun 19, 2008 6:14 pm Post subject: |
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| Technology has moved on a little since then and the current drawn would be far less. |
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peter scott
Joined: 18 Dec 2007
Posts: 7215
Location: Edinburgh
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| Posted: Thu Jun 19, 2008 6:39 pm Post subject: |
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In a PM I've suggested to 1stpop that he inserts the regulator between the "B" terminal on the gauge and his ignition switch, leaving the "T" terminal to connect to the tank sender just as was. My understanding is that the tank unit only connects between "T" and chassis.
Peter |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4236
Location: South Cheshire
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| Posted: Fri Jun 20, 2008 6:32 pm Post subject: |
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Peter
you are right, I was over complicating things in my mind!!
Dave |
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peter scott
Joined: 18 Dec 2007
Posts: 7215
Location: Edinburgh
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| Posted: Wed Jul 02, 2008 12:56 pm Post subject: |
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| ukdave2002 wrote: | Peter
you are right
Dave |
Not altogether, 1stpop pm'ed me to say he'd tried my regulator suggestion and (appropriately) it went "pop".
Peter   |
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