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post #1 of 19 (permalink) Old Sep 13th, 10, 10:19 AM Thread Starter
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Question on gas gauge voltage.

Hi guys. I know I've been reading and posting all over the forums lately trying to fix my gas gauge/sender issue and just happen to read some post in this forum. I bought a fuel gauge resister for my console fuel gauge the other day. Before I go into removing the gauge I did a reading on the volts from the plug at the rear and the meter read 6.02. Is this correct or not?

I got the sender working and meter read 9.0 to 94.2 when I tested the sender out of the car, but when I plug in the sender in the trunk the gas gauge doesn't respond to indicate the correct level as I move the float up and down. The meter also reads anywhere from 9.0 to 11.9 at the rest position on the sender and 94.2 at the all the way up position.

Am I on th right track?

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post #2 of 19 (permalink) Old Sep 13th, 10, 02:09 PM
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Re: Question on gas gauge voltage.

With the sending unit out of the tank, add a jumper from s/unit chassis to ground.
Six volts is about correct. Yes, you're on the right track.

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post #3 of 19 (permalink) Old Sep 13th, 10, 02:42 PM Thread Starter
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Re: Question on gas gauge voltage.

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Originally Posted by Everett#2390 View Post
With the sending unit out of the tank, add a jumper from s/unit chassis to ground.
Six volts is about correct. Yes, you're on the right track.
Not sure what you mean. Are you saying to jumper sender to ground and check the voltage from gauge plug thru the meter and sender to ground? In series correct?



Ok. I made a complete circuit with red lead of the meter at the gauge plug, grounded the body of the sender to the ground on the trunk brace and touched the black lead from the meter to the pin for the rheostat. The meter indicated 6.03.

What does that tell me? Should I have looked at the gauge to see if it was doing anything...I didn't.


OK, checked again. Gauge doesn't do anything making this check.


Well it looks like I just need to reinstall the tank and see what happens. The sender reads as it should and if I did the above correct then the gauge should be OK too correct? Both wires, ground and power at the sender OHM'd at .02, so those are good. I ground the gauge and it goes to empty from full and goes back to full when ungrounded.

Would it make any difference if I replaced the resister at the back of the gauge or just leave it alone? I do have a new one.

Thanks for the help.

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post #4 of 19 (permalink) Old Sep 13th, 10, 05:15 PM
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Re: Question on gas gauge voltage.

I am suggesting while the s/unit is out of tank, it needs a ground to the car body/chassis to complete the in-car circuit for fuel meter testing.
With a complete circuit, s/unit at 90 ohms, gauge should read full.
Half stroke, half full (40-60 ohms); empty (0-10 ohms), empty should be indicated on the fuel gauge.

Ohms should be measured with no power on the circuit as in checking s/unit rheostat and the tan wire continuity from gauge to ground with s/unit in place.
Six volts should be read any where along the tan wire to car body/ground with ign key in the IGN position.

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post #5 of 19 (permalink) Old Sep 13th, 10, 05:41 PM Thread Starter
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Re: Question on gas gauge voltage.

Quote:
Originally Posted by Everett#2390 View Post
I am suggesting while the s/unit is out of tank, it needs a ground to the car body/chassis to complete the in-car circuit for fuel meter testing.
With a complete circuit, s/unit at 90 ohms, gauge should read full.
Half stroke, half full (40-60 ohms); empty (0-10 ohms), empty should be indicated on the fuel gauge.

Ohms should be measured with no power on the circuit as in checking s/unit rheostat and the tan wire continuity from gauge to ground with s/unit in place.
Six volts should be read any where along the tan wire to car body/ground with ign key in the IGN position.
I get a good bench test with the sender out of the tank. With the way I had it all jumped together laying in the trunk, I got nothing with the gauge when I move the float arm. I don't even have a clue if I had things connected to make the gauge work as you are saying. At this point I still don't know if the gauge is working right with the sender. I don't think I'm getting this.

Can't I just ground the body and connect to the harness and move the float to see if the gauge will work? or doesn't it work that way?

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post #6 of 19 (permalink) Old Sep 13th, 10, 06:04 PM
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Re: Question on gas gauge voltage.

there should be a ground wire to the sending unit,everette is saying its not working right,corrosion,no contact,i ran a jumper from neg. battery post to the unit,hooked to the fuel supply line with an alligator clip 68 has a longer fuel line from unit,i hooked to it,an it started working,this checks the grd. circuit, star washer for fresh paint,without the ground it will never work,west68
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post #7 of 19 (permalink) Old Sep 13th, 10, 06:15 PM Thread Starter
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Re: Question on gas gauge voltage.

OK. I went out and checked it again. I just jumpered as if it was all installed. With ignition on, gauge read empty with sender at bottom stop. I moved the float to FULL stop and gauge only went as far as the first mark past 1/4 and no further. I believe I am getting somewhere, I think. If the meter is indicating the proper ohms, in my case 9.0 to 94.5 then the sender should be fine correct? With the gauge not registering with the sender what next? I did the radioshack resister deal earlier and only got to just over the 1/4 mark as well with 2 45 and 2 22 ohm resisters in series. Gauge needle will not go any further.

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post #8 of 19 (permalink) Old Sep 13th, 10, 06:21 PM
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Re: Question on gas gauge voltage.

Quote:
Originally Posted by 69Z28 View Post
Would it make any difference if I replaced the resister at the back of the gauge or just leave it alone?
Remove the resistor from the back of the gauge and try your sending unit again to see if gauge reads any fuel level manually selected at sending unit.

Your ohms reading of 9 to 94 ohms is correct.

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post #9 of 19 (permalink) Old Sep 13th, 10, 06:24 PM Thread Starter
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Re: Question on gas gauge voltage.

Quote:
Originally Posted by west 68 View Post
there should be a ground wire to the sending unit,everette is saying its not working right,corrosion,no contact,i ran a jumper from neg. battery post to the unit,hooked to the fuel supply line with an alligator clip 68 has a longer fuel line from unit,i hooked to it,an it started working,this checks the grd. circuit, star washer for fresh paint,without the ground it will never work,west68

I don't think I'm having a ground issue though. The ground wire on my sender is solid. I ohm'd it at the sender body connection and the other end and got an .02 reading. I checked the end connection and then thru the sender body and still came up with a .02 reading. I'm going to check it again now just to be sure.

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post #10 of 19 (permalink) Old Sep 13th, 10, 06:35 PM
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Re: Question on gas gauge voltage.

But the ground wire should be connected to the body to complete the circuit, not just within the s/unit itself.

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post #11 of 19 (permalink) Old Sep 13th, 10, 06:47 PM Thread Starter
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Re: Question on gas gauge voltage.

Quote:
Originally Posted by Everett#2390 View Post
But the griound wire should be connected to the body to complete the circuit, not just within the s/unit itself.

As in body of the sender or the car. Maybe I'm not understand the terms used. I rechecked the ground wire on the sender body, it's at .2 ohms. Good and solid. Is it possible I am not making the circuit connections right? I'm not letting this issue beat me fellas.

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post #12 of 19 (permalink) Old Sep 13th, 10, 07:00 PM
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Re: Question on gas gauge voltage.

Ground wire of the sending unit to the car body, or negative battery post.

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post #13 of 19 (permalink) Old Sep 13th, 10, 07:03 PM Thread Starter
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Re: Question on gas gauge voltage.

Quote:
Originally Posted by Everett#2390 View Post
Remove the resistor from the back of the gauge and try your sending unit again to see if gauge reads any fuel level manually selected at sending unit.

Your ohms reading of 9 to 94 ohms is correct.



That is my next step. If I do get a reading manually and the gauge is right with the sender, what does that mean? And if I don't get a good reading what does that mean?

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post #14 of 19 (permalink) Old Sep 13th, 10, 07:05 PM Thread Starter
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Re: Question on gas gauge voltage.

Quote:
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Ground wire of the sending unit to the car body, or negative battery post.
That is how I had it if connectiong to the trunk latch bracket. I'll try the connection to the battery as well.

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post #15 of 19 (permalink) Old Sep 13th, 10, 07:08 PM
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Re: Question on gas gauge voltage.

If the gauge works with no resistor, leave the resistor off.
If the gauge does not work, then a bad gauge or a stuck needle on the gauge - slap it once.

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