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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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 (http://www.mindspring.com/~mccorry) (updated 12/22/00)

[This message has been edited by mccorry (edited 01-21-2001).]

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

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
350/300HP RPO Z11

[This message has been edited by Mark C (edited 01-22-2001).]

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
'69 Camaro RS/SS-350 - Daytona Yellow
'95 Camaro Z-28 - Sebring Silver
click here to see my webpage ---> www.mindspring.com/~mccorry (http://www.mindspring.com/~mccorry) (updated 12/22/00)

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. http://www.camaros.net/forum/mad.gif

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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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 (http://www.mindspring.com/~mccorry) (updated 12/22/00)

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

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
click here to see my webpage ---> www.mindspring.com/~mccorry (http://www.mindspring.com/~mccorry) (updated 12/22/00)

Here is a shot of what I have right now....

http://images.honesty.com/imagedata/h/636/54/26365464.jpg
http://images.honesty.com/imagedata/h/636/54/26365465.jpg

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 (http://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).]

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.....
Geezer

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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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 (http://www.mindspring.com/~mccorry) (updated 1/24/01)

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

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
1969 Indy Pace Car
350/300HP RPO Z11

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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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 (http://www.mindspring.com/~mccorry) (updated 1/24/01)

Here is the circuit...as far as I can tell.
Please forgive the poor quality...I just freehanded this in Paint....

http://images.honesty.com/imagedata/h/636/55/26365578.jpg

The unlabeled item in the upper left corner is the bulb...the thing I vaporized is in the lower left marked as "diode ??".
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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 (http://www.mindspring.com/~mccorry) (updated 1/24/01)

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

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

What is the purpose of the bulb is the sending unit? Boy, this is getting complicated http://www.camaros.net/forum/confused.gif

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

Not sure....but only the originals have the bulb. I think the unit is supposed to clip into the center hole between the fuel and oil pressure guages....like this....

Must be to add more light to the fuel gauge area (as well as the dash "low fuel" light). Thats just a guess though....

http://images.honesty.com/imagedata/h/563/74/25637425.jpg

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

Mccorry,
I have a set of gauges that are shot, it has the low fuel warning light. I do not know if it works or not though. Your more than welcome to it if your interested.

Kevin

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68 Camaro SS - In Resto

After looking over the wiring diagram you posted I got curious and went to look at the one I have. Unfortunately the same component was damaged on this one. It has had another diode inserted there. The board is broken though so it will no longer work.

Kevin

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68 Camaro SS - In Resto

With a switching transistor circuit that contains a relay controlled switch, the relay coil is connected to the power supply terminal (red wire) and to the switching transistor. The diode is wired across the relays coil, so it should have one connection to the red wire and one connection to the transistor. The diode is used to suppress voltage spikes in the circuit caused by the relay being picked up.

I could see it being wired in parallel with the relay coil (one side to red wire, and one side to an internal board mounted conductor, Connecting from the red to the black wire is essentially the same thing as being wired across the coil except that the diode is across both the relay and transistor and is connected to ground all the time instead of only when the transistor is picked up. This has to put added strain on the circuit over time.

None of your photos show up anymore so I can't see your circuit diagram. But based on a typical switching transistor circuit the following should be true. (I'm no electronic engineer)

The thing with the yellow wire on it is the reed switch. This is the 12V out to the fuel light. The other side of the reed switch (common terminal) must have an internal connection to the red wire (+12V) somewhere, although it may be internal to the circuit board.

The thing with the green black, and red wires will be the transistor, the coil of the reed switch relay should be wired in series with the red wire, and one leg of the transistor.

There aren't any connections in that light socket are there? I though that the socket was just used to hold the unit into the cluster. There is no connection to the Instrument panel lights in the 4 wires that go to the sender.


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Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11

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

kdorsett, if you don't need that part...I'd appreciate if you would send it to me. I could use it to get some measurements...and maybe salvage some parts from it....

Drop me an Email...

Mark C, the pictures wouldn't load since my webpage has exceeded its allotted bandwidth for the month. I moved the pics over to another server tonight.

What you are saying is making sense. The circuit diagram is up know...check it out...

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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 (http://www.mindspring.com/~mccorry) (updated 1/24/01)

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

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

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

Well....finally figured this thing out. Ended up replacing the diode and both transistors. Seems to be working fine now.

Here is what I found out.....

Basically, this is a "stepped" transistor circuit. The first transistor is "on" until you reach a low fuel condition. At that point, this switching transistor is turned "off" which then biases the second transistor (high power) "on". This "on" condition connects the yellow wire to ground and lights the lamp.

I think I can make an adjustable circuit now that I know how this component functions.

Thanks to everyone for the help...

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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 (http://www.mindspring.com/~mccorry) (updated 2/24/01)

[This message has been edited by mccorry (edited 02-28-2001).]

[This message has been edited by mccorry (edited 02-28-2001).]

Glad to hear you finally got that bugger taken care of, HAPPY MOTORING http://www.camaros.net/forum/cool.gif

Kevin

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68 Camaro SS - In Resto

Ok,played with my low fuel light most of the day.Got lost,and frustrated,put it all together,gauge doesn't work now, is on 1/8 tank.:mad oh well. My real problem is,the loww fuel light wont light up.If I ground the sender,the gauge is on empty,and I have 3 volts at the yellow wire.The solders look good,I have a good power and ground at the module I've checked the bulb,it's good.I thought the yellow wire supplied 12 volts to the bulb,but found there is already 12 v. at the bulb,from the ign.switch.Obviously the yellow wire supplies the ground.I grounded the yellow wire,the light,lights up. If I'm understanding right,the switching transistor(squarish 3 prong)has a relay in it.I havn't a clue what a reed switch does(must be the round 3 prong thing).I also understand the part that mccorry blew up is a capacitor,to cut down on voltage spikes(I suppose the whole thing would work without it,maybe not for long,though).Anyone got a clue on testing the stuff on the circuit board.The gauge did work,until I put it all back together,so it shouldn't be the problem.

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

I finally got mine working right it was a bad ground at the fuel tank on the frame cleaned it & put a new screw in it & when I filled it up at $199.9 today it went off for the first time
It also come's when I get down to 1/4 tank now like it should
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1967 RS/SS 396 Camaro

[This message has been edited by johnnyr (edited 05-06-2001).]

dale68Z, a transistor IS an electrical relay. Think of it as a valve that is opened by applying voltage to it. When voltage is supplied to the base of the transistor, current flows thru it.

The components on the board are
1.) a diode (to suppress voltage spikes I believe).
2.) A bias transistor (this is the small black one
3.) A main switching transistor (the big round white one).

On a low fuel condition, the main tranistor is switched "on" and connects the yellow wire to ground.

My guess is that you have a bad transistor....

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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 (http://www.mindspring.com/~mccorry) (updated 3/10/01)

[This message has been edited by mccorry (edited 05-05-2001).]

I guess I should run over to radio shack,and buy both of the transistors.I had no idea a transistor was a relay!Why do they need two of them?When you bought yours,did they have the parts in stock?I felt,from the other discussions on replacing these things,that the newer stuff is physically larger.Therefore more difficult to fit into the holder.

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

Dale, unfortunately, its not that simple. I will try to dig out the part #'s I used.

I know that the main transistor was a 40W PNP and I believe the other was a basic switching PNP. I will try and find my sheet.

Also, good luck in resoldering the new components to the old board. The board is actually a ceramic wafer and I couldn't find ANYTHING that would stick to it. The solder would just bead up.....

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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 (http://www.mindspring.com/~mccorry) (updated 3/10/01)

OK...found my sheet....

The general switching transistor I used was an NPN (Radio shack part # - 276-1617).

The main switching transistor is a 40W NPN transistor (TIP31 - Part # 276-2017).

The diode was a generic silicon diode...

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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 (http://www.mindspring.com/~mccorry) (updated 3/10/01)

Mccorry,THANKS,I found I couldn't solder on the board also,seems the board soaks up the heat,and won't allow the solder to stick to the trace.The solder on my 302 car was terrible,my RS car has real nice solders.Huumm,it can be done,I know I need more heat.... I'll bust out the torches,yea thats it,torches that'll do it!! Thanks again,hope I didn't ruin my fuel gauge trying to fix the low fuel light. Dale.

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

Well,I have 1 of the transistors,the2017.On the schematic it shows a base,collector,and emitter.How do I know which one goes where?Is there any way of testing the old transistors?I really don't want to undo the solders,since they are so nice.I have to go back-I wrote down the wrong # for the other one.Thanks,Dale.

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

Now I have all the transistors,The high power one(2017) will take the placeof the round,white one that is existing.The other transistor(1617) came in a package of 5 different parts,how do I know which one to use?Sorry,I don't know jack about electronics,except I know bad solders are common.

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

Dale, all the transistors in the pack are interchangeable...they are all std. NPN switching transistors.

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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 (http://www.mindspring.com/~mccorry) (updated 5/4/01)

Sorry to ask,but what does NPN mean?I will have to guess at the connections.My guess is... emitter=output of transistor,base = the supply voltage,or ground (ground in the high volt transistor's case)that is being switched. collector= the power that "turns on "the transistor.Thanks again,Dale

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

Dale...it is confusing and I only have a very BASIC grasp on the concept...but NPN vs. PNP refers to the electron "hole" movement within the silicon chip. The type of transistor (PNP or NPN) used is dependant upon how it is placed in the circuit.

All you need to know is that this circuit takes 2 NPN transistors.

As far as connections, I am not sure how to pass on what goes where. I did make up a sketch of the "low fuel" circuit a while back. I believe it is shown earlier in this post.

Anyhow, I will try and update it with the connections....

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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 (http://www.mindspring.com/~mccorry) (updated 5/4/01)

[This message has been edited by mccorry (edited 05-06-2001).]

mccorry,www.lucent.com,has some info on transistors,I'll see if I can figure this out.Thanks,Dale. by the way,my fuel gauge wires came off the connector,the fuel gauge works now!

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

[This message has been edited by dale68z (edited 05-07-2001).]

[This message has been edited by dale68z (edited 05-07-2001).]

Here's a circuit that you can built that you can use for fuel, temp, oil, pressure, etc, has 4 separate circuits, uses 1 LM339A comparator, under $10, e-mail me if you need more info...terry
http://images.andale.com/110/124/6084307/989797757416_COMP2.jpg


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57 c-20 rat
66 c-10 panel, 350 3spd
68 c-20 lb 250, 4spd
82 Camaro, 305, 200-r4
84 Monte carlo, 305. th350
Everett, WA

WOW,I shouldn't have looked at that.I'm still working on my simple 2 transistor low fuel light.I'll knoe if it works tomorrow.(I have a feeling it will light the light all the time)Thanks,anyway,Dale.

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

Dale, this is a 2 transistor circuit!, but you can monitor 4 guages, Just lop off the right 3 circuits...

I count 4 transistors and 4 op-amps. Why do you say it is a 2-transistor circuit?

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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 (http://www.mindspring.com/~mccorry) (updated 5/18/01)

Ok...my low fuel light doesn't work,just can't get the solders to hold.Think I'll make my own.I'm to stubborn to give up!!!I can fix it,my dad is a plummer,he has all the cool tools!!!! http://www.camaros.net/forum/smile.gif

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68 z28 ,68 rs 327 ,73 454 vette, 2 goofy kids

He's saying the low fuel light is a 2 transistor circuit to perform a single function (provide a ground for an idiot light on low fuel). The drawing is of an 8 transistor circuit for 4 functions. If you want to use the drawing for the 2 transistor just cut off the last 6 transitors (3 circuits worth).


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Mark Canning
1969 Indy Pace Car
350/300HP RPO Z11