Fuel gauge at 9:00, doesn't move - Team Camaro Tech
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post #1 of 18 (permalink) Old May 29th, 10, 06:39 PM Thread Starter
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Question Fuel gauge at 9:00, doesn't move

I put the gauge cluster in yesterday and a couple things happened.... I lost my courtesy lights ??? and the fuel gauge went to 9 o'clock and stayed there.

I've read every post there is but haven't found a clue.
There's about 3 or 4 gallons in the tank, the tank ground is good and the tan power wire is connected. I shot the tan wire to ground at the tail harness and got something like 12 or 14 Ohms, which would be about 7 gallons.

Then I shot the gauge with the key on (ohms between tan and black. the red wire isn't used). Got something like 40 Ohms. That's what it SHOULD read.

So I took the connector off the gauge and Ohmed the resistor. I believe it's supposed to be in the 84 Ohm range? It's not. Checked from black (center spade) to one side of the resistor and it's a dead short. Checked to the other side of the resistor and it's like 147 Ohms. Same with checking both sides of the resistor to the tan (left spade). Short one side, 147 Ohms the other. To me that means the resistor is OK. But it isn't 84 Ohms.

I checked the tan and black wires in the connector OFF of the gauge and got the same readings I did back at the tail harness.

What's the unused center post on the back of the gauge? I can't remember if that's connected to some part of the gauge and I just can't see it because I'm upside down under the dash.

The only thing I didn't try was putting more gas in and seeing what readings I get.
Could the gauge be dead?

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post #2 of 18 (permalink) Old May 29th, 10, 08:11 PM
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Re: Fuel gauge at 9:00, doesn't move

The AIM shows three wires to the fuel gage. a "P" a"B" ana "T" the purple is ignition the black and tan you know (ground and sender)

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post #3 of 18 (permalink) Old May 30th, 10, 05:40 AM Thread Starter
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Re: Fuel gauge at 9:00, doesn't move

After a good nights sleep, it dawned on me that the resistor IS at 84 Ohms. I was reading it while it was still connected.

My fuel gauge has a third red wire (Fuel Warning) but I don't have that system so it's unused.

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post #4 of 18 (permalink) Old Jun 1st, 10, 08:29 PM Thread Starter
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Re: Fuel gauge at 9:00, doesn't move

OK... can someone tell me what these readings are telling me?

If I disconnect the tail harness and Ohm the tan fuel sender wire, I get 40 Ohms because there's about half a tank of gas in it now. Before I put more gas in tonight it read 14 Ohms with just a couple gallons.
All is good with the sender I take it.

When the tail harness is unplugged from the harness running up front, and the key is On, the fuel gauge needle moves clockwise and reads Full.
If I plug the tail harness back in the needle spins counter-clockwise past E to the 9 o'clock position and stays there no matter what I do.

I checked the tan wire at the bulkhead connector for the tail harness by the wheel well while it was unplugged and there's 8.2V on it. Just as a sanity check, there is 12V on the brown wire to the brake lights back at that connector.
With the tail harness plugged back in, the tan wire shows 8.2V on both sides of the connector.

This tells me it a bad gauge, correct?

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post #5 of 18 (permalink) Old Jun 2nd, 10, 03:29 AM
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Re: Fuel gauge at 9:00, doesn't move

Yep, bad gauge, or the stops were not installed.
90 ohms = full
45 ohms = half
22-25 ohms = 1/4 tank
11-14 ohms = 1/8 tank.
All are approximate indications.

You next gauge you can bench test with battery power and two 45 ohm resistors.
Resistors in series = full
One resistor = half
Both resistors tied together in parallel = 1/4 tank.
Or two 50 ohms resistors, more 'stock' size.

Gauge wiring:
Pink = power from the fuse panel - same power for BRAKE light, GEN light, OIL light.
Black = ground, same gauge lamp ground and turn signal indicator ground also.
Tan = sending unit.
My schematic does not show LOW FUEL, so, you're on your own.
You might remove the resistor and see what the gauge indicates.

If battery voltage on pink wire, then battery voltage should be on tan wire. Sending unit determines the current flow thus the indicating level, lower level/resistance, more current; more resistance, less current. It will be milliamperes because of the size of coil in gauge.

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Last edited by Everett#2390; Jun 2nd, 10 at 03:39 AM.
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post #6 of 18 (permalink) Old Jun 2nd, 10, 03:49 AM Thread Starter
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Re: Fuel gauge at 9:00, doesn't move

Thanks Everett

Yeah, there's a red wire in the fuel gauge connector for Low Fuel. I don't have that option and the idiot light for it isn't wired.

It's interesting that that circuit has the BRAKE and GEN lights on it. My GEN light works fine but the BRAKE light won't come on with the proportioning valve wire disconnected. I assume it would.

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post #7 of 18 (permalink) Old Jun 2nd, 10, 03:52 AM
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Re: Fuel gauge at 9:00, doesn't move

good info right here

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post #8 of 18 (permalink) Old Jun 2nd, 10, 04:16 AM
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Re: Fuel gauge at 9:00, doesn't move

Quote:
Originally Posted by HwyStarJoe View Post
Thanks Everett

My GEN light works fine but the BRAKE light won't come on with the proportioning valve wire disconnected. I assume it would.
Ground the brake wire, light should come on.

You're welcome.

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post #9 of 18 (permalink) Old Jun 2nd, 10, 06:23 AM
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Re: Fuel gauge at 9:00, doesn't move

Everett to the rescue. Thanks for the info...

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post #10 of 18 (permalink) Old Jun 2nd, 10, 08:25 AM
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Re: Fuel gauge at 9:00, doesn't move

You're welcome, Mike.

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post #11 of 18 (permalink) Old Jun 3rd, 10, 09:49 AM Thread Starter
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Re: Fuel gauge at 9:00, doesn't move

Haven't had a chance to play anymore with it. Not too concerned right now. I've got AAA.
I can always throw a cheap multimeter in the trunk and check the sender once in a while. 5 Ohms means hit the gas station!

I've got resistors. I have to remove the dash anyway to install a new light switch so I'll verify the gauge this weekend.
I can't remember but is there a way to disassemble it so I can verify it's broken or otherwise internally?

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post #12 of 18 (permalink) Old Jun 3rd, 10, 07:04 PM
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Re: Fuel gauge at 9:00, doesn't move

You should be able to place the ohmmeter leads across the gauge and see the needle move - good!

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post #13 of 18 (permalink) Old Jun 3rd, 10, 07:35 PM Thread Starter
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Re: Fuel gauge at 9:00, doesn't move

Oh! I didn't know that. I'm always under the dash while probing it. I'll get my trusty 10 year old to watch it next time.

It's not at 9:00 anymore. Now it's just real close to E. Fortunately it's easy to get to while the dash is all in, except now I can't pull it out of the carrier. I put it all back together tonight with the stereo installed and new headlight switch.
See where my priorities are?

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post #14 of 18 (permalink) Old Jun 19th, 10, 04:57 AM Thread Starter
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Re: Fuel gauge at 9:00, doesn't move

*UPDATE* and question....

Until last night when I filled it, I didn't know exactly how much gas was in the tank and the gauge was over at the 9 or 10 o'clock area when the key was on.
I filled the tank (FIRST TIME EVER!!!!! ) and the needle went to just over 1/4 tank!

I think I know why.... when I had the gauges out I probably either removed the needle or spun it on it's shaft.
Now that the tank is full, can I just spin the needle over close to F and call it good? Makes sense to me.

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post #15 of 18 (permalink) Old Jun 19th, 10, 07:02 AM
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Re: Fuel gauge at 9:00, doesn't move

You can try to 'clock' the needle upon its shaft and see what happpens from there.
Visit a TV shop or Radio Shack and get a 50 ohm resistor, more commom than a 45 ohm, and jumper one lead to ground, the other to the tan wire and look to see if gauge registers approx 1/2 tank.

Ohm disconnected tan wire to sending unit referencing ohmmeter to ground to read approx 90 ohms for full tank.

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