yet another fuel gauge question.

-
66Dartdriver

66Dartdriver

Well-Known Member
Joined
May 22, 2010
Messages
459
Reaction score
221
Location
Erie Pa.
ok purchased this 1965 dart about two months ago. the fuel gauge would only show 5/8 when full. I read a bunch of posts on here and read to ground the sending unit wire to the frame and if it registered as full on the gauge the sending unit is bad and the gauge is ok. installed new sending unit and same thing. so read some more and decided to remove the internal regulator/limiter and replace with a 5v "7805" replacement. see pic. reinstalled the gauges back in the dash turned on the key and the fuel gauge went only to 1/8 with a full tank? wth? pulled the gauges back out bench tested the gauge with the "old sending unit and it worked great, full, half and empty tank positions on the sending unit rheostat.
i figured it was a ground problem on the tank sending unit. tried an external ground strap to the frame nothing...tried a ground strap all the way to the neg term on the battery still nothing. any suggestions or what to look at next??
thanks!

IMG_0905.JPG
 
This is why you need a test "standard" and that is why you need to emulate the factory guage tester. This was a swtichbox with three resistors, and we have discussed this on here:

Hey Del, Look what I found!!! An original Miller Gauge tester!!!

c-3826-jpg.1714848381


But you don't HAVE to use a test box or even three resistors. If you have a good ohmeter, and a fuel tank sender, or a good rheostat, you can just manually move the fuel sender TO the resistance specified for full, empty, or 1/2 and then hook that up........your gauge should emulate those readings.

How to eliminate sender: your "test" sender, whatever it is made of, should give you the same reading on both/ all three gauges. If they are all off.....

1....Your test resistance may be wrong, double check with a "known good" ohmeter

2.....Both / all three gauges could be bad. Might be unlkely. Do you suspect they are damaged? Do they all read the same? but just "all off"? Then the trouble is elsewhere

3....Voltage supply troubles. Make CERTAIN your sender and cluster are properly grounded to each other. On some models, the harness connector for the PC board can be broken. The stud nuts on the gauges can be loose / corroded. Make CERTAIN you have a min. of 12.6 supply volts. DO NOT USE a battery charger!!!
 
WHAT IS THE DEAL on this connection? Is it MAKING connection?

DOH.JPG
 
67Dart273 said:
This is why you need a test "standard" and that is why you need to emulate the factory guage tester. This was a swtichbox with three resistors, and we have discussed this on here:

Hey Del, Look what I found!!! An original Miller Gauge tester!!!

c-3826-jpg.1714848381


But you don't HAVE to use a test box or even three resistors. If you have a good ohmeter, and a fuel tank sender, or a good rheostat, you can just manually move the fuel sender TO the resistance specified for full, empty, or 1/2 and then hook that up........your gauge should emulate those readings. this is how i tested the fuel gauge on the bench it worked as it should. then when i reinstalled it in the dash it just went to 1/8 tank and that was it.

How to eliminate sender: your "test" sender, whatever it is made of, should give you the same reading on both/ all three gauges. If they are all off..... so i should bench test the temp gauge too?

1....Your test resistance may be wrong, double check with a "known good" ohmeter will do

2.....Both / all three gauges could be bad. Might be unlkely. Do you suspect they are damaged? Do they all read the same? but just "all off"? Then the trouble is elsewhere as i stated the fuel guage was off and showing 5/8 at full and the temp gauge seemed to be a little off too. i dont have an oil gauge just an idiot light. it works.

3....Voltage supply troubles. Make CERTAIN your sender and cluster are properly grounded to each other. On some models, the harness connector for the PC board can be broken. The stud nuts on the gauges can be loose / corroded. Make CERTAIN you have a min. of 12.6 supply volts. DO NOT USE a battery charger!!!
Click to expand...
i didnt see any broken damaged studs or anything back there.
you have to click to expand to see the answers to your questions above.
thanks for the reply!
 
66Dartdriver said:
the yellow wire is attached to the blue connector attached to the terminal post. is that the connection you are referring to? there is nothing attached to the post with the copper cap connector
Click to expand...

The "copper cap" is where the 5V is fed (originally out of) INTO the fuel gauge. That terminal MUST have connection to that gauge stud.

With the cluster "rigged" to operate, stick your meter probe into the side and contact that stud. It should have 5V to cluster ground.

When I was talking of stud connections, not just damage or broken..........These get loose if they have not been "fiddled" with, and corroded. You need to loosen/ tighten the nuts on ALL the studs and consider replacing the nuts with "real" ones.
 
67Dart273 said:
The "copper cap" is where the 5V is fed (originally out of) INTO the fuel gauge. That terminal MUST have connection to that gauge stud.

With the cluster "rigged" to operate, stick your meter probe into the side and contact that stud. It should have 5V to cluster ground.

When I was talking of stud connections, not just damage or broken..........These get loose if they have not been "fiddled" with, and corroded. You need to loosen/ tighten the nuts on ALL the studs and consider replacing the nuts with "real" ones.
Click to expand...
i attached the "5V lead to the Temp guage post that feeds between the fuel and temp and that copper cap does show 5V to it. I will check all connections and replace nuts as well. thanks!
 
You must log in or register to reply here.
-

Back
Top