Low fuel light..... - Team Camaro Tech
Electrical & Wiring Troubleshooting electrical.

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post #1 of 41 (permalink) Old Jan 21st, 01, 12:40 PM Thread Starter
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Steve
 
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Ok....

finally got all my console gauges working....but my Low Fuel light is now staying lit. This feature wasn't working before due to a broken solder joint in the sender. I fixed it...but now it won't turn off...

I have just over 1/2 tank and the fuel gauge reads so.....

Anyone have any idea as to why this could be doing this? I have the 4 wires (yellow, red, black, and green) from the low fuel sending unit hooked up as normal...

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post #2 of 41 (permalink) Old Jan 21st, 01, 06:30 PM
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Steve I asked the same question several months ago I tried all of the suggestions & never did fix it completely! I have got it down to a dim glow & it works right when I get real low on fuel, I'll be watching to see if they can come up with something new.

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Johnny 1967RS/SS 396 Camaro
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post #3 of 41 (permalink) Old Jan 22nd, 01, 04:32 AM
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Try swapping the two wires at the back of the fuel gauge in the cluster. The Red one should be on the 12V side (from Fuse) of the fuel gauge (outer terminal with red cluster wire), the green should be on the side closest to the sender inner terminal with tan cluster wire). Black is ground, and yellow is to the light. If you grounded the black wire to the front gauge pod did you remember to add a jumper to the rear pod, because that is where the wiring harness ground attaches. If you don't have the jumper then the front gauge pod isn't grounded and the fuel gauge won't work.

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Mark Canning
1969 Indy Pace Car
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[This message has been edited by Mark C (edited 01-22-2001).]
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post #4 of 41 (permalink) Old Jan 22nd, 01, 12:34 PM Thread Starter
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All my gauges are working....and the ground strap is there.

I have the red wire from the low fuel sender connected to the outer post and the green wire connected to the centermost post. The black is connected to the bottom middle (ground).

I will check to ensure that the low fuel sender is grounded correctly.

Any other ideas?

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Steve McCorry - Central Ohio Camaro Club
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'95 Camaro Z-28 - Sebring Silver
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post #5 of 41 (permalink) Old Jan 22nd, 01, 04:28 PM Thread Starter
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Well...I did get it to work finally...was another busted solder joint...

It worked for about 30 seconds before poof! The diode in it shorted on something an vaporized.

Looks like I'm in the market for a new low fuel sending unit. Anyone got one that they wanna sell?

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'95 Camaro Z-28 - Sebring Silver
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post #6 of 41 (permalink) Old Jan 23rd, 01, 06:08 PM
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What part did you let the smoke out of? I don't recall a diode on the low fuel electronics but I might be able to figure out a replacement component
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post #7 of 41 (permalink) Old Jan 24th, 01, 03:14 PM Thread Starter
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There are 3 basic board mounted components...

1.) Appears to be a switching transistor. Has 3 leads.
2.) Another transistor or possibly a small potentiometer. Again...3 board mounted leads.
3.) A diode, reed switch, or resistor. This is what I smoked!

I have made a drawing of the circuit if that would help...or I can snap a picture of the components....

Any help is appreciated!

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Steve McCorry - Central Ohio Camaro Club
'69 Camaro RS/SS-350 - Daytona Yellow
'95 Camaro Z-28 - Sebring Silver
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post #8 of 41 (permalink) Old Jan 24th, 01, 05:30 PM Thread Starter
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Here is a shot of what I have right now....




You can see the two ?? transistors ?? on the board...and the two remaining ends of the other part (one is on the board still while the other is on the desk).

The ends, when attached to the board, appeared to look like this ---| |---- configuration so I thought it might be a capacitor or diode....

I hope this helps....
Can anyone identify these components?

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Steve McCorry - Central Ohio Camaro Club
'69 Camaro RS/SS-350 - Daytona Yellow
'95 Camaro Z-28 - Sebring Silver
click here to see my webpage ---> www.mindspring.com/~mccorry (updated 1/24/01)

[This message has been edited by mccorry (edited 01-24-2001).]

[This message has been edited by mccorry (edited 01-26-2001).]

[This message has been edited by mccorry (edited 01-26-2001).]
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post #9 of 41 (permalink) Old Jan 24th, 01, 07:15 PM
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I would think It's a capacitor, they blow like that. Diodes & resistors don't usually vanish like that...the 67 I took apart doesn't look the same and a 66 Buick isn't close...I'll send picts anyway..Oh and even if you can get the part number it can't be cross referenced...GM numbers made for GM...ask me how I know.....
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post #10 of 41 (permalink) Old Jan 24th, 01, 07:32 PM Thread Starter
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Geezer....just got your email with the photos...

In the second picture you sent me....with all the components lined up....the part on the far left is IT. That is EXACTLY what mine looked like before it went poof.

It is a diode? I'll send you a reply Email also...

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post #11 of 41 (permalink) Old Jan 25th, 01, 03:46 AM
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OK, now that you have it all apart Steve, tell me Just how does the low fuel light work ? I assume it gets a signal from the gauge at a certian location of the gauge needle.

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post #12 of 41 (permalink) Old Jan 25th, 01, 05:31 AM
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It looks like a high voltage switching transistor, and a relay operated reed switch. The switching transistor is connected across the fixed resistor on the back of the fuel guage. As the resistance of the sender circuit decreases (going towards empty)the amount of current in the circuit which increases the voltage drop across the fixed resistor. When the voltage drop gets to the switching transistors setpoint the output of the transistor picks up the coil for the reed switch closing the reed switch. The reed switch provides the output to the Fuel light throough the yellow wire.

The red wire provides 12V to the circuit to operate the relay and provide power out the yellow wire to the light. It probably also provides a reference voltage to the switching transistor. The green wire is the signal wire to the switching transistor, black is ground.

The yellow wire should be attached to the reed switch contact, as should the Red wire, although it may do this through the circuit board.

Switching transistor circuits like this do use either or both resistors and diodes.

What color wire attaches to the piece that is melted, Red, Green, Black or yellow.


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Mark Canning
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post #13 of 41 (permalink) Old Jan 25th, 01, 05:02 PM Thread Starter
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Mark C, which do you think is the switching transistor and which is the reed switch?

I am guessing the transistor is the black component while the reed switch is the black/white part?

Looks like the part I fried was indeed a diode based on what Geezer has told me.

The melted part was connected between the red and the black wires. It is also connected to the yellow wire through a board mounted resistance strip. I'll try to get the circuit drawn out....


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'95 Camaro Z-28 - Sebring Silver
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post #14 of 41 (permalink) Old Jan 25th, 01, 05:31 PM Thread Starter
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Here is the circuit...as far as I can tell.
Please forgive the poor quality...I just freehanded this in Paint....



The unlabeled item in the upper left corner is the bulb...the thing I vaporized is in the lower left marked as "diode ??".
------------------
Steve McCorry - Central Ohio Camaro Club
'69 Camaro RS/SS-350 - Daytona Yellow
'95 Camaro Z-28 - Sebring Silver
click here to see my webpage ---> www.mindspring.com/~mccorry (updated 1/24/01)

[This message has been edited by mccorry (edited 01-25-2001).]

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post #15 of 41 (permalink) Old Jan 25th, 01, 05:44 PM
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What is the purpose of the bulb is the sending unit? Boy, this is getting complicated

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69 rallye green X77 Z/28,1967 SS 396 Conv. 1974 c-10 454 swb
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