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another fuel gauge issue

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Old 04-14-2012, 05:23 PM   #1
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another fuel gauge issue

Thanks to all whom can help. I have been reading some past threads on fuel gauges. I need to know a few answers if possible. I have a 70 Duster. First I tried grounding sending unit wire and got no response on gauge. I pulled cluster. I powered the gauge and it works. Also need to mention the temp gauge is not working. I replaced voltage limiter with one I had. Here are my readings. on one side of gauge it reades varying voltage of around 5v. The other side of the gauge has nothing( according to power probe it shows ground) Using my power probe I grounded the already grounded other side of gauge and no affect on gauge. What am I missing?? I went to LF kick panel and checked connector there and tried grounding dark blue wire and same nothing.
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Old 04-14-2012, 05:28 PM   #2
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voltage regulator maybe ?
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Old 04-14-2012, 05:40 PM   #3
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figured the reg was working due to the varying 5 v voltage. also I replaced it with another one but the condition of both are unknown. Just not sure what I should read with my volt meter at the gauge if its working properly
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Old 04-14-2012, 07:28 PM   #4
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Read this thread. There are several issues that can happen with your cluster

http://www.forabodiesonly.com/mopar/....php?p=1811915

Repost of my post:

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Originally Posted by 67Dart273 View Post
There are several issues that crop up in these clusters

First, make sure your switched ignition (dark blue) or "ignition run" power to the cluster is solid

Second, make sure your sender wire and sender are not the problem

Then....

1 The cluster harness connector can be loose/ corroded

The PC board connector pins can be loose/ broken corroded

So solder the pins if possible, in my case SEVERAL of the pins were broken/ loose, corroded, bad shape. So I elected to go with a pair of "Molex" style connectors which I bought at RadShak. I just soldered leads to the board traces and brought them out to the Molex connectors. If you search the site, there are several posts about guys fixing these connectors

2 The PC board / cluster can have a poor ground

Loosen/ tighten all board mount screws, clean the board if necessary, and either solder a wire to the board ground, or attach a lead wire to a board ground screw. Bring this out and screw to the column support

3 The VR can be faulty, even though it is somewhat functional, may not be the correct output

The VR SOCKET in the PC board may not be making good contact with the board

Replace the VR, and check resistance and examine the brass fingers that make the contacts. On my 67, I soldered short wires from the brass clips to the board traces. They were NOT making contact on mine

4 The gauge nuts ("fake" sheet metal) may be loose/ corroded, as can be the PC board surface

Replace the nuts with real nuts, clean the board if necessary, and don't overtighten them.

5 And of course the gauge can be faulty

After you've checked and fixed everything else, this is a possibility. Both fuel and temp use the same sender resistance, this is where the test resistances come into play. You can either get resistors from (limited selection) at Radio Shack, or places like Mouser Electronics or Digikey

the resistance to obtain MT, 1/2, and full (or "hot") are

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)

Another way, if you have your fuel sender out, is to lay it out, move it until you get the resistance listed above, and then hook to the sender end of the gauge with test leads.

The gauge needs a properly working VR, or you can rig a supply (battery) of 5--5 1/2V
You can buy battery holders from RadShack, and if you can rob some AA cells out of some of your remotes, etc, and they are "down" just a little from new, they should be very close

And, for example, if you think the temp gauge is OK, you can compare readings between the two gauges. With the same voltage to the gauges, and the same sender resistances, they should read very close to the same. That should give you and idea if one is way off from the other.
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Old 04-15-2012, 05:43 AM   #5
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Thanks for the advise. I did read this thread. I will read again to make sure the issues are not related to the list. I ordered an voltage limiter last night. Does anyone know what I should see on a correctly working fuel gauge (voltage wise) at the gauge?
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Old 04-15-2012, 07:17 AM   #6
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Mecanical limieters create a pulsing voltage all around 2.x to 3.x volts which averages around 5 to 6 volts. A good analog meter will show the average while a digital meter will flash numbers like crazy.
A solid state reulator provide a constant 5 volts seen on any volt meter.
Please note; The instrument panel will not work properly while dangling from the harness connectors. It needs a chassis ground.
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Old 04-15-2012, 08:07 AM   #7
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oh dang Redfish I had no idea. Thats exactly how im checking it. What if I run a ground wire to it?
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Old 04-15-2012, 12:09 PM   #8
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Yep, needs to be grounded. That is EXACTLY why I recommend ADDING a ground wire in my post above. You either need to solder a wire to one of the board ground traces, or install one under a screw and make SURE it is clean and tight. Leave it long enough, about a foot or a little more, that you can bolt it to the column support before you put the cluster clear in.

(You actually don't need the ground for the gauges, you need it for the voltage limiter)
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Old 04-15-2012, 12:33 PM   #9
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Redfish is the man when it comes to this .
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Old 04-15-2012, 07:13 PM   #10
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Thanks to all of you for the help.
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Old 04-21-2012, 07:39 PM   #11
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I wanted to post a fix to the fuel gauge and temp gauge. I took everyones advise above. Thanks for the input. What I did was changed the regulator on circuit board. I also changed the nuts on gauges to real nuts and not the wavy ones. I also ran a ground wire to the panel and tightend all screws around the cluster. I know the fix wasnt the regulator because the old one was working. But walla after all that everything works.
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Old 04-21-2012, 07:53 PM   #12
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!! Good fer ya !!
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