Fuel guage repair

Help Support 7173Mustangs.com:

MooseStang

Well-known member
Joined
Jul 1, 2021
Messages
181
Reaction score
70
Location
Texas
My Car
72 Q-code Vert
I recently installed instrument cluster lens, great upgrade. However,  as I followed the instructions regarding the ribbon circuit and verifying all of the blue domes were intact (mine looked brand new btw), while tightening one of the nuts on the back of the fuel gauge, I  heard a slight "pop". I figured it was something just settling in,  so I continued to put everything back together.  Lights were great.  Tonight,  went for a drive,  no fuel guage reading.  After a fair amount of effort,  I finally found that the plastic holding the stud had cracked,  allowing it to spin, which broke the wire connection.   Great. Anyone know how to repair this? Or am I looking at buying another guage?

20210831_213350.jpg

 

MooseStang

Well-known member
Joined
Jul 1, 2021
Messages
181
Reaction score
70
Location
Texas
My Car
72 Q-code Vert
Update. I decided to try a mechanical connection, so I shoved the end of the broken wire in the hole, and then shoved in the stud.  Put some voltage to it,  and it works.  Here's another pic, actually both sides are cracked.   Should I drop some super glue at the base of the studs? Will that be enough to keep the loose one from spinning?

20210831_222205.jpg

 

Aus73Mach1

Well-known member
Joined
Aug 5, 2019
Messages
113
Reaction score
51
Location
QLD Australia
My Car
1973 Mach 1 Sports Roof.
Q code. 351-4V
C6 Auto, 3.25 Rear Axle, AC, Power steering.
Had the same problem with my gauges. While the stud is out make sure the lock nut spins freely before reassembly. I sanded the flat section of the stud and applied a blob of solder. While the heater wire does not "attract" solder, I cleaned the end, put a slight twist in the wire and encased it in the blob of solder on the stud. Put it back together and super glued the stud and cracked plastic backing. Everything held together on reassembly and guages worked fine.

 

MooseStang

Well-known member
Joined
Jul 1, 2021
Messages
181
Reaction score
70
Location
Texas
My Car
72 Q-code Vert
Thanks for the confirmation.  I think I'll stick with the mechanical and not solder for now.  Will just apply the super glue.   I would advise anyone going through the led upgrade to be VERY CAUTIOUS when removing the ribbon circuit to inspect the blue domes, or possibly skip the step entirely.

 

MooseStang

Well-known member
Joined
Jul 1, 2021
Messages
181
Reaction score
70
Location
Texas
My Car
72 Q-code Vert
My guage needs calibration.  If you look at the pics, you'll see two arms with adjustment teeth.   Does anybody know how to do this adjustment?   I would think it should be based on applying a particular voltage and then moving the adjustment arms to achieve the proper needle reading,  yes?

 

MooseStang

Well-known member
Joined
Jul 1, 2021
Messages
181
Reaction score
70
Location
Texas
My Car
72 Q-code Vert
I found this info on another forum https://www.vintage-mustang.com/threads/inaccurate-fuel-gauge.850386/page-2

If you are able to make a simple potentiometer, as suggested earlier, you can independently test you sending unit, and your gauge.
You will find out if the sender is supplying the correct resistance at the various levels. With the arm in the upper position it should read 10 ohms. Full.
At Empty, 78 ohms.
Then apply your potentiometer device to the gauge. Use 5 volt input to one post, and put the potentiometer between the other post and Ground, and dial up the ohms and then see how the gauge reads at the levels of resistance you input.... 78 is empty, 10 is full.


So now I just need to go find me some ohms.

 

MooseStang

Well-known member
Joined
Jul 1, 2021
Messages
181
Reaction score
70
Location
Texas
My Car
72 Q-code Vert
Without me doing anything, the crazy thing started working again, well, at least it's reading about where I think it should be.  I'll have to do a complete fill up to check.

 

Bobby

Well-known member
Joined
Sep 24, 2018
Messages
157
Reaction score
24
Location
League City, TX
My Car
1972 Mach 1
Hey, just found your post on the fuel gauge.  I updated my cluster with new Autometer gauges.  I have saved my old gauges and you are welcome to my old fuel gauge if you can’t get yours operational. I’m down in League City. 

 

MooseStang

Well-known member
Joined
Jul 1, 2021
Messages
181
Reaction score
70
Location
Texas
My Car
72 Q-code Vert
Thanks for the offer.  I "think" mine may be working better now.  I'll have to fill it and then run it empty after I get my diff issue resolved.

 

Bobby

Well-known member
Joined
Sep 24, 2018
Messages
157
Reaction score
24
Location
League City, TX
My Car
1972 Mach 1
I had replace my gas tank about two years ago and put in a repro sender and all was good. My my tach had to be rebuilt when I got my Mach 1 rewired since it was designed to work in series with the ignition system it was a serious point of failure. If the tach ever failed, the engine would not run.  The rebuilt tach had issues right away and would intermittently bounce back and forth from 1500 to 2000 rpm. I then decided to replace all the gauges since the alternator gauge didn’t work either. Anyway as those things go, you fix one problem and immediately create another.  The new fuel gauge was giving crazy readings. I called Autometer tech support and they said that the problem was the aftermarket repro sending unit. The resistance readings between the old sender an new were the same at full and empty but different every where else. The only fix was to get on OEM sender or return the new unit back to be rebuilt to work with the repro sender. That would change the color and create a mismatch. I found a new old stock sender on eBay and installed it and sure enough, works good now.  So I have all the old gauges stored. 

 
Top