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Automotive/1990 Ford Tempo fuel gauge

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Expert: - 6/25/2007


Question
QUESTION: I have a 1990 Ford Tempo.  The gas gauge does not work.  Could you tell me how to fix it?  Is it something that has to be replaced or is there a fuse or something easy like that to fix?  Thanks

ANSWER: The fuse that supplies power to a fuel gauge supplies power to other instruments as well so, if no other instruments nor other systems are out, a fuse would not be your problem.

Beyond that, it could be that the sender in the tank has become defective by becoming an open circuit, or the gauge readout itself has similarly failed, or it could just be as simple as a broken connection at a terminal or within a wire itself.  An open wire will generally exhibit visible physical damage.  Further investigation would be done using a multimeter in its resistance range or a voltmeter to check continuity from the power supply end of the system, back to the tank sender terminal.

As indicated in my profile, I do not have a shop manual for your car, so can be no more specific than this.  Whatever part or parts you might need should NOT be pricey, especially if you or a friend are doing the installation.

Good luck ... EGK

---------- FOLLOW-UP ----------

QUESTION: Thank you for that information.  The power locks are also out on the car.  Do you know of any place I could get a diagram of the fuse box?  It may have some missing, but I do not know what belongs.  There seems to be very few fuses, maybe three or four.  I think it may be missing some.  Thank you for your help.

Answer
You could go after this from a number of sources ...

(1)  Check out you local library to see if the collection includes a shop manual for the Tempo and similar Fords of that era

(2)  See if you can get your shop to provide you the information.  Print-outs could be had from the Mitchell Repair Information Company database, as well as from the OEM's data

(3)  Perhaps buy the shop manual?  The car is a 93 and, if you are planning to keep it, this is not a bad investment

(4)  definitely last ... does Haynes publish a book?
My experience with the Haynes books is that they are very sparse on details, and often have errors.

It should not be much of a problem getting a friendly shop to print you out something however.  Go for a wiring diagram or diagrams while you are at it.

Happy hunting, and cheers ... EGK

PS ... Thinking further about your problem:
I do not have first-hand experience with the Tempo or Taurus, but four fuses only in a fuse box (is this the only one?) along with several empty bays does have me wondering if you might not simply be missing some fuses.  It could be that your problems will be solved simply by getting the right fuses into place.  

It could also be that a former owner did not replace one or more fuses after some electrical system misadventure.  Visible evidence of this might be physical damage to a wiring harness.  Or perhaps a power door lock solenoid burned out and developed a fault to the vehicle ground, taking out the fuse.  Any replacement fuses would also burn out, so someone at some point likely just elected to abandon the function, and left the fuse out.

There is an adage in EE: All electrical and electronic devices run on SMOKE!  Provided the smoke stays in, the component is fine.  Let the smoke out, and the component fails.  Trying to force the smoke back in won't make it better.

I believe that this is called the Philogiston Principle, and it is applied with tongue firmly in cheek.

Again, happy hunting ... EGK  

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Ernest (Ernie) Kenward

Expertise

The challenges I most enjoy are thoughtful technical questions of a trouble-shooting nature in both electrical, power electronic and mechanical systems, mainly automotive but also machine control and small-machine PLC applications. Please note, however, that I am NOT a walking shop manual! I DO, however, make it a point to have those manuals and other service literature for those vehicles I DO own, and highly recommend that anyone serious about maintenance or modification of their vehicles do the same; MOST of your answers WILL be found there. For that matter, I do NOT go out of my way to acquire shop manuals for any vehicle I do NOT own! That being the case, any general query to me along the lines of "What is the meaning of this code read from the ECU of my 2015 XYZ?" or "Where is the fuse for the windshield washer pump found?" (try your car's electrical distribution panel for a start!) will not go far. What I do offer is a pretty good collection of literature, insights and hands-on experience with 1950s to 1980's Ford products (plus a developing database of information and practice with the Mercedes diesel cars), along with an engineering perspective and the ability to design and implement custom control, electrical and mechanical subsystems for vehicles. For that reason, I am happy to make my thoughts and efforts available to those who are of like mind and/or are seriously making a point of learning about their vehicles. Use the Opportunity to Learn!

Experience

A key skill in my work and hobby pursuits both is STRATEGIC TROUBLESHOOTING. I am a senior instructor in Electrical Engineering Technology at a leading Canadian polytechnic, my areas being Electrical Power and Industrial Control, electrical and electronics design and manufacturing, and AutoCAD and related CAD/CAE software - plus equipment problem-solving and new equipment design and prototyping. Hobby-wise, I have 30-plus years of experience in auto restoration, mostly in electrical and mechanical systems. Ongoing projects include a 1959 Edsel Corsair, my 1978 Ford E250 class-B motorhome conversion, and the care and upkeep of my Mercedes 300CD. My vehicles become engineering test beds for electrical and mechanical upgrades as ideas present themselves. This includes the design and production of circuit boards to restore or enhance features for which no OEM replacement parts are obtainable, or where better specifications or reliability can be had via newer concepts. Regarding the E250 RV conversion, I designed and continue to revise a custom power distribution system, managed by a Programmable Controller (PLC); this has made most revisions as easy as uploading new firmware as I develop it. The "mini" PLC is a powerful device for custom automotive control systems. One good example (there are many) would be the Moeller "Easy Relay"; these offer a wealth of control, monitoring and variable-and-status display options for such projects. A good example project which has worked well is that one for my RV noted above, which has been on the job - revised in firmware only - for a decade now. It is a load management and charging control system to avoid the sulfation-induced early failure that often befalls deep-cycle batteries used in RV power applications. The battery installed in 2003 lasted long enough to more tnan pay for the PLC that contributed to its longer life ... and the PLC will be there for the next battery as well!

Organizations
IEEE - senior member ... past WCC Student Activities; SME - senior member ... past chair, greater Vancouver chapter chair 318; Edsel Owners' Club - have served in various capacities on chapter executive during seventies; have been Power and Driveline resource on the Edsel Owners' Club "E-team" for more than a decade.

Education/Credentials
Graduate of UBC

Awards and Honors
Certificates of appreciation from IEEE and SME for work in student and chapter activities

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