Fuel Gauge Problem - Team Camaro Tech
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post #1 of 29 (permalink) Old Jan 19th, 09, 09:46 AM Thread Starter
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Fuel Gauge Problem

I know there are search threads but I was hoping to find an expert to talk to.Fuel Sending Unit is putting out 89 Ohms,I installed new resistor in Fuel gauge,panel is grounded.It read 1/2 tank with nothing on it,put the 12v to it when I cranked the car it went past Full,I think it is ground related.But everything seems to have a good ground. Will it hurt anything other than reading Full ? Any help is apreciated.I am pulling my hair out after installing the Console.
Thanks.........alan
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post #2 of 29 (permalink) Old Jan 19th, 09, 06:58 PM
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Re: Fuel Gauge Problem

Seems like the needle needs to come off and be "clocked" correctly, or close to it.
Remove the tan wire at the sending unit and install a 45, 48, 0r 50 ohm resistor to ground = 1/2 tank. Or a borrowed resistor decade box from Mr TV repairman.

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post #3 of 29 (permalink) Old Jan 20th, 09, 06:17 PM Thread Starter
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Re: Fuel Gauge Problem

Quote:
Originally Posted by Everett#2390 View Post
Seems like the needle needs to come off and be "clocked" correctly, or close to it.
Remove the tan wire at the sending unit and install a 45, 48, 0r 50 ohm resistor to ground = 1/2 tank. Or a borrowed resistor decade box from Mr TV repairman.
Thanks Everett,When above statement said Fuel Sending Unit puts out 89 Ohm's this was before installing in the tank (at simulated Full tank),Update.... I ran a temp. ground jumper from sending unit ground to battery/chassis ground ,no fix. Battery unhooked,I checked ohm's in trunk ,tan to ground gave me 44 ohm's,checked other side of plug-in connector, tan to ground 44 ohm's,Can you help me understand what it means to clock ? Is this resistor temporary to get it to clock ? I am a High Voltage Journeyman Lineman for a power co. but this dc thing sometimes has me scratching my head.Again Thanks for the reply and your help,I really would like to fix this but if I have to tear that console apart 1 more time I might put an aftermarket gauge in the glove box. I really apreciate your help..........take care....alan

Last edited by 98blackburb; Jan 20th, 09 at 06:47 PM.
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post #4 of 29 (permalink) Old Jan 20th, 09, 06:49 PM
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Re: Fuel Gauge Problem

Hi 98blackburb,

Is this on a 1st gen or a 98 Camaro (4th gen)?

Did you install a new repro sending unit?

On my 1st Gen, I purchase two bad repro sending units (giving bad readings) that I finally change for a Spectra Premium Sending Unit P/N FG104C (3/8 Single Line) that I purchased from NAPA.

Good Luck, Daniel.

Daniel,
1969 SS-350 Camaro, Hugger Orange
2005 Black Mustang GT

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post #5 of 29 (permalink) Old Jan 20th, 09, 07:02 PM
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Re: Fuel Gauge Problem

Hopefully, this will help.

http://www.chevelles.com/techref/ftecref18.html

alan
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post #6 of 29 (permalink) Old Jan 20th, 09, 07:31 PM Thread Starter
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Re: Fuel Gauge Problem

Daniel... Yes 1st. gen,1969 Camaro SS ,It's even Hugger Orange like yours Nice car you have there. Console gauges,I too bought a new sending unit (bad), replaced with a new good 89.7 Ohm's before installation. Sad to say but it happened to me from a Well known Camaro place too.I am thinking of taking off Console cover and run a temp. jumper to gauge face and see if it moves it even though panel is grounded,kind of a long shot. Alan ,Thanks for the link ,read that too,Waiting on Everett with this clocking thing. I'm listening if you guys got anything else.......Thanks guys..........alan
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post #7 of 29 (permalink) Old Jan 21st, 09, 10:15 AM
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Re: Fuel Gauge Problem

I would say with 44 ohms through the sending unit to ground, its telling me you have 1/2 tank of fuel. So gauge should read 1/2 tank.

Tan wire tied to ground, gauge should read empty. Tan wire with a 90 or 100 ohm resistor to ground should read full tank. Of course, all these actions/resistance values connected, with power on, gauge should indicate the cheated level.

In your first post, you said 90 ohms, appiled voltage with key on, and gauge went past FULL. Personally, I found the final FULL indication about three marks past full if gauge was in the cluster. On a console gauge, I would think it would indicate just past F. So I said to clock the gauge, meaning if the needle slams against full rather than rest against F, and if gauge reads something other than alittle more than half (44 ohms), then I would think the needle needs to come off its axis and get pressed back on in the proper spot, mechanically align the needle to the scale to match its electrical input or current flowing.

The gauge has two coils, and the resistance value, 0-90 ohms of the sending unit, determines the amount of current through the coils creating a magnetic field and this field "pulls" the needle weight/axis to indicate on the scale.

I believe console gauges have three posts on it? One for 12V input, one for ground, and one for sending unit. All I have is for a cluster gauge, no console gauge. Your 44 ohms into the harness to the gauge, if I read correctly, should not be there, unless the gauge(?) resistor is there and you're reading it, but still, shouldn't be ohms there to ground. I would really rather not get inside the gauge. I may be too deep into this thinking.

Of course, I too could have too many ohms..............

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post #8 of 29 (permalink) Old Jan 21st, 09, 03:32 PM Thread Starter
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Re: Fuel Gauge Problem

Everett,you are correct as to my 1st. post,sometimes I get ahead of myself,As far as you having too many ohm's....I doubt that ,I highly respect your opinion and I hold it in high regard, you're a pretty sharp cookie....Good info there Everett ,My Fuel gauge is next to my Oil Pressure Gauge

I believe I have it grounded right,I'm wondering if the Gauge itself is not connecting good enough for the ground,I am going to take off console cover and jumper the gauge metal with a ground to test that theory.Longshot..... Is my resistor in right?
I really apreciate the input and your help,not looking forward to the console apart thing. Real close to running a new gauge in the glovebox hidden .As far as removing and re-clocking,I'm assuming it is a pressed fit.
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post #9 of 29 (permalink) Old Jan 21st, 09, 03:47 PM
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Re: Fuel Gauge Problem

Before I go any further, I would like to see a schematic of a console gauge set-up. I'll have to check my 68 Assembly manual for one. Might be one inside and I not see it as I was rapid-thumbing through the manual. Any help where these might go? Low level light?

On the resistor, I see a thin green wire and a red(?) thin wire on the other side. But I see a pink(?) wire - power and a tan wire on the plug to the gauge.

To make troubleshooting easier, I would temp place a variable resistor between the ground lug/to dash ground/battery neg post, make it one connection, and the resistor wiper to the tan wire terminal on the gauge. Apply bat power to red/pink terminal gauge and see gauge indication. While varying resistance of resistor from 0-90 ohms, gauge should follow.

Thanks for the vote of confidence - maybe it is a lack of ohms.............let me ask my wife....not!

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post #10 of 29 (permalink) Old Jan 21st, 09, 06:07 PM Thread Starter
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Re: Fuel Gauge Problem

LOL.........be careful now if Momma ain't happy ain't nobody happy. I told my wife just the other night ....you're right I'm wrong, I'm sorry......she kissed me then I went and ordered more Camaro parts.......yes those small wires are Low Fuel Indicator lights.I am running different console lights each having thier own ground but the cluster is also connected to the gauge panel so all the potential is the same.I bought a 47 ohm resistor today but garage is too cold tonight, 37* in Fla. ,You believe that ? Here is a schematic..............I do have an Automatic......thanks Everett for your help

Better view of connections before lights installed,I do have a new resistor in place of old blade style
Hard to see but small black goes to big black,bulb is no longer there, Rick's told me that was for Corvettes for that year

Last edited by 98blackburb; Jan 21st, 09 at 06:24 PM.
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post #11 of 29 (permalink) Old Jan 21st, 09, 06:15 PM
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Re: Fuel Gauge Problem

I looked at my Assembly Manual and U17-A2 shows the harness hookup to the console gauges. The sketch (didn't have CAD back in "67) does not show a resistor. So it might a gauge thing rather than a harness item.

However, I do remember gauges back in this time frame, both OE and aftermarket, had a voltage dropping resistor, not just for the fuel gauge, but for the others, water temp and oil pressure, as the idea was not to send a full 12V to the sending units, only 5 volts.

A schematic of console gauges woiuld be nice. Maybe some one here will scan one and post it.

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post #12 of 29 (permalink) Old Jan 21st, 09, 06:16 PM
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Re: Fuel Gauge Problem

If you gauge is new they have the resistor already built into the windings so you don't need the external one. Resistor itself should measure somewhere around 42 ohms (temperature sender resistor measures around 86 ohms) Original ones look just alike, the newer ceramic versions have different color paint daubs on them, pink and blue I think, I don't know which one is which.

Having the wrong resistor (higher resistance) in there (or 2 resistors in series) will make it read beyond full.

When you disconnect the sender at the connector in the trunk and short it to ground (the wire going back to the guage) does the needle go to empty, or stay above full?

Mark Canning
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post #13 of 29 (permalink) Old Jan 21st, 09, 06:20 PM Thread Starter
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Re: Fuel Gauge Problem

Mark , I have'nt got around to it yet, maybe tommorow will be warmer in the garage. Us Fla. boys can't handle the cold....Thanks Mark
Everett I added a schematic up above.Thanks guys for your help........alan
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post #14 of 29 (permalink) Old Jan 21st, 09, 06:24 PM Thread Starter
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Re: Fuel Gauge Problem

Mark it is an old gauge.............thanks
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post #15 of 29 (permalink) Old Jan 21st, 09, 06:25 PM
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Re: Fuel Gauge Problem

Thanks for the schematic! Ah-ha! Unplug the gauge and without the low level light, attach the 47 ohm to the tan terminal and the other end of the resistor to ground or negative power source. Attach the pink terminal to 12v power source -gauge should indicate 1/2 tank approximately.

Did you get two 47 ohm resistors? Put them in series, one attached to the other -
lead to res to lead to lead to res to lead = 90 ohms and gauge should read full.
Put them in parallel, 22 ohms, and should indicate 1/4 tank.

The needle is a press fit onto its shaft.

You're welcome.

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