Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace) - Page 3 - Team Camaro Tech
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post #31 of 103 (permalink) Old Jul 29th, 13, 07:58 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Could you elaborate on this please.
Quote:
Originally Posted by 69-Pace View Post
To test the sender you need to test the ohms (resistance) with a simple multimeter.
You measure across the loose lead in the trunk to the connector to the gauge. You
should read anything from 0 to 90 (empty to full). If you are getting something close to what you think is in the tank, the sender maybe ok.
Measure the loose lead to the connector to teh gauge is unclear to me.

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post #32 of 103 (permalink) Old Jul 29th, 13, 08:41 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Okay...nevermind last post.

I disconnected the brown wire from the trunk pan. Turned the key in the ignition...Needle rises to past the F on the gauge.

Question...what happens if you GND the loose lead going to the sender? I screwed up and did that first. I seem to be my own worst enemy the last few days.

I then GNDed the brown wire on the harness side and the needle went to E...but not past it.

I checked with the multi-meter set at 200 Ohm across the two wires (still disconnected)
The reading was 111.7

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post #33 of 103 (permalink) Old Jul 29th, 13, 09:36 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

111 is way too high and should then read past full. If that is correct the LFWM should not be activating.

You were reading the loose connector-wire and not the receptacle that goes forward to the gauge right?

Sounds like the resistor is or the gauge is bad. Also run the Ohm's meter over through the two leads of just the resistor and post a picture of the resistor or describe the unit.


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post #34 of 103 (permalink) Old Jul 29th, 13, 10:35 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Quote:
Originally Posted by 69-Pace View Post
111 is way too high and should then read past full. If that is correct the LFWM should not be activating.

You were reading the loose connector-wire and not the receptacle that goes forward to the gauge right?

Sounds like the resistor is or the gauge is bad. Also run the Ohm's meter over through the two leads of just the resistor and post a picture of the resistor or describe the unit.
I should note the LFWM is no longer lighting like it did yesterday...it was a one time thing.

The gauge did go past full when I disconnected the brown wire and turned the key. But did not go past empty when I grounded it...it stopped right at Empty.

I put the multi meter between the two disconnected trunk connectors...was that not the right way to check? Black lead on gauge side, red lead on sender side.

I'm not sure what you mean by "run the Ohm's meter over through the two leads"

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post #35 of 103 (permalink) Old Jul 29th, 13, 11:13 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

If you want to test the sending unit, disconnect the tan wire from the plug in the trunk. One lead of your MM to the wire coming from the sender, the other lead to ground. 0 ohms is empty, 90 ohms is full. If you know approx how mush fuel you have you can get a general idea.


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post #36 of 103 (permalink) Old Jul 29th, 13, 11:23 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Quote:
Originally Posted by BPOS View Post
If you want to test the sending unit, disconnect the tan wire from the plug in the trunk. One lead of your MM to the wire coming from the sender, the other lead to ground. 0 ohms is empty, 90 ohms is full. If you know approx how mush fuel you have you can get a general idea.
Okay...thanks. This is why I was confused by the instructions at the top of the thread that say:


To test the sender you need to test the ohms (resistance) with a simple multimeter.
You measure across the loose lead in the trunk to the connector to the gauge.


I just measured per your directions and it reads 56 Ohms...which makes sense since I have a little less than 3/4 tank of gas.

Here is what I know so far:

Brown wire disconnected in trunk, key on = Reads past full
Brown wire in trunk going to gauge grounded, key on = Reads right at empty (does not go past empty)
Sending unit reading at 56 Ohms with little less the 3/4 tank of gas.

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post #37 of 103 (permalink) Old Jul 30th, 13, 12:05 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Everything sounds good so far - have you checked the sending unit ground wire. Will be near the front of the passenger's gas tank strap

Good troubleshooting guide a couple of posts down here: http://www.chevelles.com/forums/showthread.php?t=53519


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post #38 of 103 (permalink) Old Jul 30th, 13, 12:45 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Quote:
Originally Posted by BPOS View Post
Everything sounds good so far - have you checked the sending unit ground wire. Will be near the front of the passenger's gas tank strap

Good troubleshooting guide a couple of posts down here: http://www.chevelles.com/forums/showthread.php?t=53519

Haven't checked the gnd wire...but as of a couple days ago I was having no issues with the gas gauge. My recent "meltdown" caused me to think I may have damaged the gauge, it used to just move down to empty when turning the key off, now it stays put... but it was mentioned by 69-Pace that either way is normal. I also thought I damaged the LFWM due to it going on once after I re-wired my melted GND wires. It has not come back on again.

Actually, I've never had the fuel light go on at all in the past...I usually fill up before the car gets too low. I'm wondering if the LFWM has been bad all along. Any way to test this?

I'd still like to check the resistor...but I was unclear on 69-Pace's directions on checking that.

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post #39 of 103 (permalink) Old Jul 30th, 13, 04:21 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Unscrew the resistor card from the rear of the gauge.
Test Ohm's side to side. Inspect for damaged such as rust, or broken/melted wire on the card.

The LFWM basically is a gauge without a face.
At a set point the yellow wire either grounds to trip the light or power is feed to trip the light.
I think 68 powers the yellow but I'm away from my notes.

56 Ohm's is a little high to trip the module. Most went at 1/4 to 1/8 of a tank, but some after market units were higher, and some people rigged theirs to trip earlier. You can also buy a variable set point replacement unit.


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post #40 of 103 (permalink) Old Jul 30th, 13, 09:51 AM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Quote:
Originally Posted by 69-Pace View Post
Unscrew the resistor card from the rear of the gauge.
Test Ohm's side to side. Inspect for damaged such as rust, or broken/melted wire on the card.

The LFWM basically is a gauge without a face.
At a set point the yellow wire either grounds to trip the light or power is feed to trip the light.
I think 68 powers the yellow but I'm away from my notes.

56 Ohm's is a little high to trip the module. Most went at 1/4 to 1/8 of a tank, but some after market units were higher, and some people rigged theirs to trip earlier. You can also buy a variable set point replacement unit.
Got it...will measure tonight. Hey...I'll even remember to disconnect the battery BEFORE messing with connections this time.

Really suspect that my LFWM has never come on under normal circumstances.

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post #41 of 103 (permalink) Old Jul 30th, 13, 01:53 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Well you can test the module with a 0-100 ohm potentiometer. To figure out what is the set point of your module, here are a few questions: Does your module have any markings or clips on the top? Thick or thin gauge wires?


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post #42 of 103 (permalink) Old Jul 30th, 13, 08:08 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Okay. Resistor physically looks good (pic 1) and measures 86.6 Ohm across the leads.

Pic 2 is of the bottom of the LFWM... Pic 3 is of the top

I see no corrosion anywhere (I am in Cali, it's pretty dry here).

THe LFWM does have some yellow/rusty color on some of the solder. The brownish circuit board has some black residue (as seen in pic) that is between the leads that attach to it.

I see no markings on the LFWM. THe wires for it are very thin.




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post #43 of 103 (permalink) Old Jul 30th, 13, 09:19 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Also...as a sanity check...I can't find the proper wiring for the module in my assembly manual.

This is how the module was wired as you are looking at it mounted to the cluster...is this right?

light yellow wire - left stud
dark red wire - right stud
light brown wire - center/lower stud

*(YELLOW) ______________(RED)
*
*
*_________(BROWN)

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post #44 of 103 (permalink) Old Jul 30th, 13, 10:25 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Hum its late and I'm rusty but flipped over so you are looking at the rear of the gauge pod, oil is on the lower left fuel on the lower right.

The console gauge pod came as a sub assembly so I don't remember if the module is shown or discussed in either 68 or 69's AIM. I am confused on your module wires. The unit looks factory original but it should have four wires. Yellow, Green, Red, and Black.

In theory for the 68/69 the yellow lead from the LFWM is directly connected to the yellow in the harness. This is the ground path for the FUEL light on the dash. The green is connected to the left terminal lug of the fuel gauge back and red on the outside terminal, black on the middle.

Yes 86 or 87 Ohm's is good for a factory resistor.

And your FUEL is lit all the time?


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post #45 of 103 (permalink) Old Jul 30th, 13, 10:44 PM
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Re: Gas Gauge Failure. . .How to fix...Thank you, Brian (69 Pace)

Quote:
Originally Posted by 69-Pace View Post
Hum its late and I'm rusty but flipped over so you are looking at the rear of the gauge pod, oil is on the lower left fuel on the lower right.

The console gauge pod came as a sub assembly so I don't remember if the module is shown or discussed in either 68 or 69's AIM. I am confused on your module wires. The unit looks factory original but it should have four wires. Yellow, Green, Red, and Black.

In theory for the 68/69 the yellow lead from the LFWM is directly connected to the yellow in the harness. This is the ground path for the FUEL light on the dash. The green is connected to the left terminal lug of the fuel gauge back and red on the outside terminal, black on the middle.

Yes 86 or 87 Ohm's is good for a factory resistor.

And your FUEL is lit all the time?
So looking toward the BACK of the car at the back of the gauge pod...OIL on the left, fuel on the right.
The four wires are thicker bright yellow from the connector then thinner light brown, light yellow and dark red coming out of the module.

Fuel light only went on once after I rewired my GND's after the meltdown. It's never been on any other time since I've owned the car. I always wondered why it didn't work.

When you say green is connected to left terminal...are you talking as if you are looking toward the FRONT of the car?

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