I've encountered another issue w/ my 68 Dart, I thought someone might know the answers. My Fuel Gauge (and temp too I guess) has recently quit on me and I thought I knew why.

Now in the past, when I first got the car the F & T gauges were not working but I fixed them by getting a new Voltage limiter and repairing a circuit break in the printed circuit board. When I first dealt w/ this I wasn't sure that my repairs had fixed it, because when I'd turn the key (to test the repair) the fuel gauge would race to the FULL side. It was later that I realized I had neglected to re-connect the ground at the dash under the steering column..when I did that the F gauge behaved.

Up 'till now all has been well, until the F gauge stopped working last week. Upon closer inspection I found that the wire I ran from the pin (1 of 5 pins) to the break in the circuit, had broke apart where I soldered the wire to the thin copper-like circuit. That surely was the cause, and I re-soldered at the point where it broke (better this time). I turned the key for the test, and fully expected the gauge to move to the right, like I explained above (before I ground the dash) how it races to the FULL side.

To my surprise the gauge did not move. I took out my testing light and started testing everything. All the fuses were good. I touched my tester to the 4 screws that hold the Fuel & Temp gauges to circuit board( 2 for each gauge), and the light flashed/pulsed as it is supposed to do. Everything was checking proper but something was amiss.

The only thing that I wasn't sure about was when I touched my light tester to the 5 pins on the left side( these are the pins wiring harness connects to ). While connected I touched the pin the represented the GAS gauge, the light would slowly pulse and the needle on the gauge would slowly start to move to the right. Only when I stopped touching the pin w/ the tester, would the gauge go back down. So touching the pin caused the gauge to move but I don't know why the tester would cause that. Also I read that the tester light should pulse when touching the screws for the F & T gauges but I don't recall reading what it should do when touching the corresponding pins.. should they also make the light pulse or stay lit?

I hope I have described the situation well enough for folks to help. I'm not sure how to make sense of the results I'm getting w/ my test light, at least in regards to touching the pins, but perhaps it's telling some fellow something. Perhaps you know what I should do and I would appreciate whatever you can tell me.

THANKS!!

Your fuel gauge is not seeing pulsed power from the instrument cluster voltage regulator; you've got a(nother) break in that circuit. It began working when you connected the tester because the tester provided a current path.

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Too many people who were born on third base actually believe they've hit a triple.

Thanks for being prompt!

When I touch the Fuel or Temp affiliated pins connected to the harness w/ the tester, should the light pulse like when I touch the Fuel/Temp screws, or should the light stay constant? I'm just wondering. This is/was the last good printed circuit board, I tried using the one I had just for parts but it behaved the same. Although I cant see any damage to the circuits anywhere..I suppose there must be one somehow like you say.

Do you have any good tips about what I should do now or where one can get a replacement printed circuit board for a 68 Dart?

As always, your most helpful

Did it stay on empty?


Are you touching the dark blue wire that goes to the sending unit in the tank?

Danny

QUESTION 1: Yup it stayed on E. I filled up on gas and the needle didn't budge, I knew something was wrong.

QUESTION 2: Yes, I was touching the PIN that connects to the dark blue wire (while the wiring harness was connected)

-This may be stupidity on my part but I never connected the ground for the dash instrument panel, the one that connects under the steering column. ..Could this be the cause of my problem??

THANKS

The last '68 A-body I worked on had the pin to the fuel sender on the board right where the round connector plugs in get slightly loose - it would sometimes work and sometimes not work.

If you don't have any ground to the voltage limiter, (the mechanical ones at least) will send +12V continuously to the gauges, making them peg. I'd recommend see if you've pulsing 12V right at the sender and work your way back to where it's not getting through.

You can repair the runners on the board fairly easily by using stiff bare copper wire of ~14 gauge or a little smaller, bending it to follow the stock routing, and carefully soldering it to what's left of the runners. Tack it in place with epoxy and give it a coat of insulation (Glyptol or Liquid tape) and it ought to last forever.

Are you saying to check the sender at the fuel tank? I didn't know the sender there would pulse the light on my tester.

This is exactly what I did the first time I had a break in on of the copper circuit runners. Only I forgot to tack it, and it came apart after awhile, due to the shaking from the wind via the cool air vents. Which is why I thought that by re-repairing the break the fuel gauge would work just like before...but NO!

Here are some pictures of what I'm working with. The copper runner that needed repairing was the one that comes from the the middle pin, which on my wiring schematic is the voltage regulator pin. Again, these are pics showing the most recent repair job that I had to do because the first repair attempt here eventually came undone. Both repairs were at the same place you see.

Checking a gas gauge with a test light or multi-meter can be confusing. If you supply a ground to the sender wire, a working fuel gauge will go to full. I think that might be what’s happening with the test light. It’s not a very good ground through the element in the bulb, so the gauge moves slowly, and it’s flashing because it’s picking up the voltage coming from the gauge.

To check the gauge, take the wire off of the sender, or anywhere between the gauge and the sender, and touch it to the body, the gauge should go to full. That would mean you have a sender problem or the sender isn’t grounded.
Could be. It's easy to rule out by connecting it.

Danny

Sounds like a cold solder joint, or in other words the solder is not conducting. Desolder the connections you made, and reclean the copper strips & pin until nice and shiny. Resolder using rosin core solder making sure that you heat both the copper, wire, and pin enough so the solder flows out in a nice smooth drop.

I just took a second look at your board, and I have to agree with my self; cold solder joint.

I think that your test light is acting like a jumper bypassing the bad connection. But, because the filament in the test bulb has considerable resistance, and only at 5 volts, you are able to see the change brightness as the points open and close in the limiter.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

At the fuel tank a simple incandescent test light will blink 1-2 Hz; it may even be a little unsteady, and when 1st turned on may take 5-15 seconds to start blinking. It is quite obvious - the light will get pulsing 12V and nothing. A typical test light will make the gauge read ~1/3 full scale, but that will depend on the bulb in the tester.

The test light must be well grounded and often the gas tanks are poorly grounded. There's a special little metal jumper to short the gas tank nipple to the fuel line; if often rusts apart.

If you don't see the pulsing at the tank, next check the bulkhead connector, then the round plug, then the runner on the board.

good luck!

I did do the re-solder and I feel that now that connection joint must be good...here's why. I hadn't driven the car 'till yesterday and the Temp gauge (and the other gauges) was functioning properly. Only the Fuel gauge has the problem. If I'm thinking correctly, that my re-soldering joint was bad, then the Temp & the Fuel gauge both wouldn't work..true? As it stands right now the Fuel gauge is my only issue.

NOTE: When I drove the car yesterday I put in $20 bucks worth of fuel and for just a moment when I pulled out of the station, I noticed that the fuel gauge needle move up just a hair and stayed for a couple of minutes but then eventually settled back down below the E...it never moved again.

Any thoughts on this?

Thanks

Perhaps a partially gas filled sending unit float. Did you pull the wire at the tank, ground it out, and observe if the gage moved to full? If so, I vote for a sunk float.

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I haven't had the time yet to get under there, not to mention I need someone to watch the Fuel needle whilst I do it. Hopefully, I can get it together by Friday. Just so that I'm following, if I ground out the wire at the tank the fuel needle should go to full correct? Further, if the needle does not move than the problem is somewhere along that wire heading forward towards the dash, instrument panel and so on..correct?

If it turns out to be a sunk float, does that mean I need a new fuel tank sending unit? Seems like a rough installation process to do that.

"sigh"

scottdart: Easy; looooog jumper wire so you can see the dash, and find a good ground. Good circuit = gage points to full.
No, just a float, or if it is copper perhaps you can drain it, and solder up the pin hole. I recall a reference here to a Ford float being adaptable. Someone will know here will know that part number.
Not so rough, but surely a PIA. I'm not sure if you need to pull the tank or not to access the sending unit. If so get some help with the tank project.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC