I found this schmatic for a low fuel gauge but what changes would I have to make (if any) to make the circuit light one of the instrument panel light bulbs rather than an LED?
Suppost the link would be helpful
http://strickerfarms.rwisp.com/Finale%20Roadster/Disk%2010/lowfuelchevy.jpg

[This message has been edited by Phil (edited 02-26-2006).]

Phil,

where is the schematic? (Never mind)

[This message has been edited by alex de jorge (edited 02-26-2006).]

I guess I'm very lucky- both of my Fieros' fuel gages read correctly( they both go down to E )

Good for you. Mine does not. Initially it was even worse. I guess since the car sat for a while the gauge was way off. Now though, it is much better. I'll run out of gas with an 1/8 tank left.

The circuit is a simple voltage comparitor. Pin 2 has a voltage divider on it. (The variable pot (VR)should go to ground by the way) This is to adjust the voltage on pin 2 to set when the light comes on. The voltage from the fuel gauge is input to pin 3. The 741 compares the voltage on pin 2 and 3 and if one is higher then the other the output on pin 6 switches and lights the LED. You could take pin 6 and connect a 4.7K resistor to the base of a 2n2222 transistor with it's base tied to ground and it's collector to a small Radio Shack relay and a 1K resistor to +12. The relay would then be used to light a dash light. I could draw up a add-on schematic and some part #'s if you need but should be fairly simple.

Dodgerunner,

That sounds good. Would you?

Just to throw a monkey wrench into the works - could it be rigged to connect to the instrument panel lights - they have a constant 12V+ applied and they light when grounded?

what is that 741 thing? is it something you can get from radio shack or is it already on the car

The 741 is a called an Op amp. Radio Shack part # 276-007 99 cents.

No it not in the car this would be a total add on circuit..

Since you could drive a small relay with the output you could run most any lights on the dash you want as long as you relay met the current requirments. Catalog #: 275-005 or Catalog #: 275-241 should work.

I'll draw up a quick drawing of the driver for the relay. Will post back in a day or two.

Would take longer if someone wanted a full layout.

[This message has been edited by Dodgerunner (edited 02-26-2006).]

Would anyone be interested in a low fuel indicator if I came up with a working unit.

Could build up a unit that you would connected via four wires to the Fuel gauge wire, +12, Ground, and something like the Door Ajar light.

You would set when you want the light to come on (how low the fuel was) via a variable resistor (pot). Could even have the light flash at a slow rate, something like every 30 seconds. The output would be driven by a relay so should be able to drive several different lights, etc.

quote Originally posted by Dodgerunner: Would anyone be interested in a low fuel indicator if I came up with a working unit. Could build up a unit that you would connected via four wires to the Fuel gauge wire, +12, Ground, and something like the Door Ajar light. You would set when you want the light to come on (how low the fuel was) via a variable resistor (pot). Could even have the light flash at a slow rate, something like every 30 seconds. The output would be driven by a relay so should be able to drive several different lights, etc.

Umm...Like Yea. I hate runnig out of gas.

quote Originally posted by Dodgerunner: Would anyone be interested in a low fuel indicator if I came up with a working unit. Could build up a unit that you would connected via four wires to the Fuel gauge wire, +12, Ground, and something like the Door Ajar light. You would set when you want the light to come on (how low the fuel was) via a variable resistor (pot). Could even have the light flash at a slow rate, something like every 30 seconds. The output would be driven by a relay so should be able to drive several different lights, etc.

That would be so cool, I'd be happy to pay for it. Let me know, I like installing items into my car that appear stock and this fits the bill nicely. -Jason

Here is the link the above was "borrowed" from http://www.westol.com/~beaurega/gas.htm

All the homework has been done for you:

https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20050818-2-059238.html

If somebody is building one, can you do one for me ?

Yeah, I would be in for one of those.
Had one in my Olds and my wifes Caddy has one now and I like it.