Fuel Guage No working???

[xory72]

Hey all,

So I took my guage cluster out over the winter to do a major cleaning (getting dust out from behind the guage glass & replacing some bulbs). I put it all back together and everything works but the fuel guage.

The fuel needle is sitting above the "1" (full) mark and I know my tank is not full.

Did I move the guage by mistake while I had it apart, higher then where the fuel actually is, therefor it is not reading?

How would I reset this? Should I fill my tank and take the guage cluster back out and set the fuel guage to the full line? Do I set the needle to empty and it will realloctae it self? Is there way test the guage to make sure the guage actually works?

Thanks for you help in advance everyone.

Darrin

 

[xory72]

Does anyone have any advice on this. I saw a very old post back in 2004 where a guys switch to white face gauges and his fuel gauge stopped working.

There were a couple of replies with suggestions, but the thread ended without noting the actual fix.

Hopefully someone can chime in.

Thanks,
Darrin

 

[AdvansCPAP]

It sounds like you could have broke it while putting back together. It's very sensitive and just over tightening the screws will mess it up. Buy a new one for 45.00 and problem solved. Just don't touch the needle or tighten the screws too much.

 

[johnboy]

This is just speculation,but after working on several watches, I would think the hand is a press fit on the post [cannonpinion] and the hand can be re- positioned to accurately reflect the proper level. It may have gotten knocked out of position when it was out of the cluster.

 

[OLDMNSX]

It sounds to me like you have an open circuit between the gauge and the fuel tank sending unit. This could be caused from a number of things.
1. Bad connection at the back of the instrument panel.
2. Broken wire in the gauge itself.
Since this is where the last maintenance procedure occured, this is where I would start. When you tightened down the mounting bolts you may have broken a wire as noted in a previous thread. Pull out the gauge cluster and take it apart again. I bet that you find a broken wire, or poor connection.

The fuel quantity indicating system is a resistance measuring design. So if the fuel sending unit is not connected to the gauge then there is no resistance and so the gauge will indicate full, or over full. As the level of fuel in the tank decreases, the resistance in the indicating signal from the float sending unit increases, causing the gauge needle to indicate a lower level, or for a better term, the voltage is being limited going to the gauge.

There is "NO" move the needle to "RESET" it. You can put the needle anywhere you want and it won't make any difference until you power up the electrical system and the gauge reads what the sending unit is saying for resistance.

Brad

 

[xory72]

Hey guys,

Thanks for the replies and ideas. I will try your siggestions out tonight or over the weekend.

As mentioned, the gauge cluster was taken out and I cleaned it all, reassembled and put it back. Since this is the only area that I touched, I will start from here. I may have to replace the gauge.

I will repost when I find the problem, but thanks for giving ideas where to start.

Darrin

 

[NSXT]

OLDMSX is close, but not quite correct.
From the online service manual, look at pages 23-126 and 23-135.
Page 23-135 of the online manual says sending unit resistance is:

Full tank = 2 to 5 ohms
Mid tank = 25 to 39 ohms
Empty tank = 105 to 110 ohms

This means that for the gauge to read above Full, the sending unit sensor wire is shorted to ground, not open circuit.

That being said, a problem with ground connection at the gauge will also cause the pegged at full reading, since the electromagnet gauge mechanism isn't getting proper current. If I were to guess, I would guess the ground connection at the gauge is bad. Power is evidently available, otherwise the gauge would not move at all.

The connector to the gauge cluster should be checked for bent/broken pins, as well as ensure power, ground and sensor signal are all correct at the gauge.

 

[xory72]

OLDMSX is close, but not quite correct.
From the online service manual, look at pages 23-126 and 23-135.
Page 23-135 of the online manual says sending unit resistance is:

Full tank = 2 to 5 ohms
Mid tank = 25 to 39 ohms
Empty tank = 105 to 110 ohms

This means that for the gauge to read above Full, the sending unit sensor wire is shorted to ground, not open circuit.

That being said, a problem with ground connection at the gauge will also cause the pegged at full reading, since the electromagnet gauge mechanism isn't getting proper current. If I were to guess, I would guess the ground connection at the gauge is bad. Power is evidently available, otherwise the gauge would not move at all.

The connector to the gauge cluster should be checked for bent/broken pins, as well as ensure power, ground and sensor signal are all correct at the gauge.

NSXT,

Makes sense ... thanks! I am going check the manual and will trouble shoot from there. I am going take the gauge cluster out again and recheck the pins etc. I guess what I need to do is determine if the gauge still works and work backwards from there.

Thanks for you advice and I will re-post with the out come.

Darrin

 

[xory72]

Hey all!

I just wanted to post to let you know I fixed my fuel gauge today. Through all your advice, the manual and process of ellimination I found the probelm in a matter of no time.

First test I did was what the manual suggested and test the wires from the fuel sending unit to the gauge then turning the ignition on. I got a reading of 10.26 V. It was not between the 5-8V as the manual indicated. That was why the guage was sitting higher then FULL. I then I tested another ground to make sure I had a good ground ... same reading ... 10.26 V

I then tested the fuel sending unit while still in the tank. The reading was 26.5 ohm. This meant I had soemwhere around half a tank of fuel according to the manual. Just to make sure I took sending unit out and tested it and all checked out per manual specs.

I now took the gauges out. I then tested the YEL/WHT from the fuel sender end and the YEL/WHT at the gauge connector end (green connector) to check continuity. Tested fine. I did the same for ground it was fine. This test confirmed that the problem was in the gauge!

I took the guage out to inspect it. I tested the 2 resistors on the guage and the they tested fine (75 ohm & 62 ohm). Then I noticed 2 things. I guess when putiing the gauge back in the cluster, I over tighten the screws and it turned the posts disconnectiong the resistor and breaking the little hair like copper wire.

Once discovering this, I soldered the resistor back to it's pole and then being real patient and easy with the solder iron, I actually soldered the copper wires back together.

I reinstalled everything and BAM ... just over half a tank of fuel!

What caused this was when I reinstalled the gauge after cleaning I over tightened the screws which the twisted the pole turning the post and breaking the connection of the copper wire and resistor. So if you ever take your gauges out, simply snug the screws that holds the gauges to the circuit board.

Thanks for all your help. I managed to fix this when I thought I was going to have to order a new fuel / volt gauge.

Thanks for you ideas, advice etc.

Darrin :biggrin:

 

[OLDMNSX]

OLDMSX is close, but not quite correct.
From the online service manual, look at pages 23-126 and 23-135.
Page 23-135 of the online manual says sending unit resistance is:

If I were to guess, I would guess the ground connection at the gauge is bad.

Hey NSXT you are too kind (VERY PROFESSIONAL). I screwed up, I should have taken the time to look at the manual FIRST before I opened up my BIG MOUTH. I was shooting from the hip from old information from past experiences. No excuse. Thanks for covering my mistake to keep the information correct.
I owe you one.
Brad

 

[NSXT]

The only thing incorrect was describing 'open circuit' as 'no resistance'. An open circuit is very high (infinite) resistance, a shorted circuit is no (zero) resistance.