69 fuel and temp gauge not working

[Trav_450R 10]

OK so, in my familes 69 Coupe the tempature and fuel gauges have not been working for a while, the fuel gauge had its moments where it would tell me how much fuel was in the tank, and then just drop back down to empty and now it just doesnt work at all... I've been meaning to ask this on here for a while, I've posted on a could threads that were already in motion on a gauge problem that seemed relivant, but no reply. Dad thinks it might be the sending unit on the back of the block, but that wouldnt really explain why the fuel gauge isnt working either correct? Could it be something inside on the gauge panel?

[ashleesmach1 28]

Could be the CVU (constant volt unit) on the back of the dash gauge panel. It's easy to replace but not easy to get too. The Temp, Oil and fuel gauges get 5volts dc from the cvu. so I would check that first. Then check each sending unit and then the gauges. There is an article in May 2010 pages 40-46 of Mustang Monthly how to troubleshoot all these. It may be on their web site as well. Also check the printed ciruitboard for lifted runs and broken ones. Good luck!

[ashleesmach1 28]

here is the web site for troubleshooting your gauges http://www.mustangmonthly.com/techarticles/mump_1005_ford_mustang_instrument_panel_troubleshooting/index.html

[relic1864 10]

Just went through the same thing a while back on my 69 coupe. Since you only want to take the dash pad and instrument pannel off only one time you need to order everything you need to replace this first time. It is no fun taking all this off several times like I did.First thing you need to do is order a new instrument cluster voltage regulator. You might as well order a new instrument circuit board too. While you are ordering go ahead and get all new light bulbs for all the lights behind the dash. I went with the new LED light bulbs. Next order the replacement cardboard guage holders and the protective covers that go over the rear of the screws that hold the guages in place. These cardboard holders through time sometimes warp and cause the guages to touch the dash pannel guage openings and ground out the guages. Grounding out one guage will cause all of them not to work. After you get all your new parts in start removing the dash pad and instrument pannel. The speedometer cable has a white tab you push down to release it. This will be brittle through the age of the car and sometimes breaks off like mine did. So now I just push it back on and so far it still stays in place and my speedometer still works. One more thing I did to make sure I had more insulation when putting the guages back in was to put black electrical atound the metal guage openings so that if a guage touched it would not touch the metal of the dash housing. Believe me this entire job is no fun and it took me several attempts to get the fuel and temp guage back to working. My alternator guage and oil pressure guage still needs replacing but I know its the guage on both of them broken and not them grounding out. I still haven't fixed them due to the hard time it took getting the other two guages working. I just don't want to take everything back appart right now to attempt replacing the other two guages. As long as the fuel and temp are working I'm ok.

[Trav_450R 10]

Thanks for your help guys! Damn Relic you've got a shopping list lol. Dads wanting to see if the plastic contacts need cleaned and see what that does, then i think we'll try the CVU deal... Im a dummy when it comes to electrical shit

[dennyb68 11]

If the oil works and the others dont it wouldnt be the cvu.I would suspect the gauges are grounded to the metal housing. It took me a few times and some re-engineering of Fords design and it all works fine now.

[Trav_450R 10]

All the other gauges still work, the amp, speedo (even though its off) and the oil pressure. Just the fuel and water temps don't

[Max Power 74]

Speedo isn't relevant. It's cable driven, not electrical. Removing the dash isn't that big of a deal. After a couple time you will get real good at it.

[69RavenConv 286]

Before you take the dash apart, unplug the wire at your water temp sender, stick a nail in it and ground it to the chassis or engine block. If your gauge moves, your cluster is ok and your sender is bad. Do it quickly, don't leave it grounded for too long. It should go full scale at a dead short to ground.

 

You can repeat the process for the fuel sender under the gas tank.

[Trav_450R 10]

Before you take the dash apart, unplug the wire at your water temp sender, stick a nail in it and ground it to the chassis or engine block. If your gauge moves, your cluster is ok and your sender is bad. Do it quickly, don't leave it grounded for too long. It should go full scale at a dead short to ground.

 

You can repeat the process for the fuel sender under the gas tank.

 

Just run them to any safe ground?

[69RavenConv 286]

Yep.