Erratic Fuel Gauge, cannot find ground

[CoachKarl]

I am trying to figure out what the ground point is for the fuel gauge sender on my 95 Windstar. Here is my dilemma. For years this gauge has behaved erratically. It either shows the correct fuel level or drifts to empty. I've disconnected the harness at the fuel tank to diagnose this problem, expecting the gauge to show empty when I throw the key. Instead, it shoots to "full" without me grounding the wire. Now I suspect I have a short, and am preparing to trace the wire back to the front of the van looking for a worn harness. I don't understand though, why, if I have a short circuit, the fuel gauge works at all? Have any of you witnessed this sort of trouble before? Please Help.

[CoachKarl]

Allow me to answer my own question. I'm trying to solve this problem using the Hayes Windstar book from 1998. There is a discrepancey. Back in the electrical chapter (section 12-12), it says that the gauge should "jump to full" when you ground the sending unit wire. I believe that it should read "Jump to empty". The fuel system chapter, (section 4-8) discusses the impedence of the sending unit, "160 ohms when full, 15 ohms when empty". I think this means that impedence is greatest when gauge reads full, and least when tank reads empty. I now believe that my harness is OK, and my Windstar is suffering from a faulty fuel gauge sender. I will post again after I replace it.

[CoachKarl]

Fixed! Replacing the sending unit in the gas tank fixed the fuel gauge. So, if your fuel gauge is intermittently going to "Empty", disconnect the electrical connection just in front of the gas tank. Turn on the ignition. If the needle rises to "Full" with the harness disconnected and shows "Empty" when you ground the yellow/white wire, the fuel sending unit in the tank is bad.

[12Ounce]

Good Info! Thnx!

I've bought the replacement pump/sender unit but have been dreading the task. My pump is blowing "fuel pump" relay quite often. Figure its trying to tell me something. Better get it replaced before I get stranded.

About the circuit diagrams in Haynes -- don't expect too much. Ford makes too many year-to-year changes. You can buy a diagram book for your specific model from Helminc.com for approx $35. One on the best maintenance tools you can have.

[CoachKarl]

Back to square 1, fuel gauge drifted to empty, after 3 trips. This problem is intermittant, and not critical (If we remember to reset the trip odometer every fuel fill.) I knew this one was going to be painful to fix. I got the bull by the horns here, I went to the trouble of dropping the gas tank and putting in a new sender, (and a new fuel pump, because . . hey, . . who wants to ever do this job twice?) Boy I wish I could fix this! Any idea's anyone? How about that antislosh thing behind the cluster? Anybody been there?

[12Ounce]

You are making me recall a fuel gauge problem that I once had on a mid-80's Escort. It was very unreliable. A co-worker suggested replacing a "voltage regulator" that resided on the printed circuit "board" of the instrument cluster. I had never heard of such, but after getting one from the dealer and installing all was well. I think the thing was call an "IVR". Instrument Voltage Regulator????

Don't know if that could be your problem or not.

[DRW1000]

I had the same IVR on my 86 Mustang. It is indeed a voltage regulator. It is very important that the voltage be correct for the gauges and although I can't remember all of the details I know I changed it because I had a gauge or two giving unbelievable readings. Most gauges (Fuel and temp) are meter movements that measure current flow (much like an old fashioned ammeter or voltmeter). The known resistances at either end of the scale (160 ohms and 15 ohms will cause deflections of a calibrated amount. If the voltage through the meter circuit is incorrect then the deflection will vary from the factory setting since Current (deflection of the needle) = Voltage / Resistance.

[CoachKarl]

Thank you, I'll look into an IVR. I chased the yellow (sender) wire back from the tank and sprayed contact cleaner in three harness connectors. 1. at the tank. 2. where the aux heater/AC is, and 3. under the hood release. I found a ground wire screwed into the floor there loose. I filed it and soldered it home! (Guess I fixed something, probably the remote key entry that I don't use.) I'll check into the voltage regulator DRW, 12oz. Either of you know a way to bypass that $60 (US) anti slosh thingamabob? I suspect this thing more because all the other gauges work fine.

[12Ounce]

I don't have a diagram for your year vehicle, but I do have one for a '97 tracer. They may be similar. (I don't see a "IVR" by the way).

There is a yellow wire that goes back to the fuel pump module, with a black/grn wire that goes on from the tank sender module to ground. The resistances are 145ohm-full and 22ohm-empty. The yellow wire goes to terminal #6 on the "anti-slosh/bulb-prove-out module" on the instrument panel". Conductors from terminals #4 and #5 (grnd), of this module, go on to the fuel gauge. Blk/grn is also the ground wire color of the instrument panel, and blk/yel is the 12v supply for the fuel gauge. (Lift #4 and #6 from the module and connect together???)

Hopes this is the same for your unit and will help.

[CoachKarl]

Gauge has worked so far. Stay posted.

[DRW1000]

I re-read my post and feel it may not be clear. I was not saying that I know your vehicle has the regulator. I was stating that I had a car that did have the voltage regulator 12ounce mentioned and what it does. It may very well have been an older design not used any more.

Sorry for any confusion

[CoachKarl]

Thanks, DRW. The gauge is still working. I'm not going to dig into the dash until it fails again. My latest adventure has me in the passenger side door swapping out a speaker, and fixing the window motor with the butt of a screwdriver.

[CoachKarl]

The fuel gauge has performed flawlessly for more than a month. The problem must have been a faulty connection in one of two harness connectors under the vehicle. In both cases, I "fixed" them by distorting the female part of the connector of the yellow/white wire with a 4 penny finishing nail, and sealing the connection with some white grease. Thank you all. Hope this helps someone.