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Reed
Supercharged
Joined: 03 Nov 2002
Posts: 8515
Location: Fircrest, WA
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Post subject:
Homebrew tool C3826 instrument cluster testing tool?
(Wed Sep 21, 2011 11:06 am)
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Anyone who has read the diagnostic section of their factory service manual has come across the mention of "Tool C3826" or "C3826A." This is the tool that has three settings- "E", "1/2" and "F" and is used to test the dash gauges in many years of Mopar cars and trucks. I can't find a source for these tools, but reading the FSM leads me to believe that this tool is basically a three position variable resistor- "E" would be maximum resistance, indicating an empty gas tank, "1/2" would be 1/2 resistance, and "F" would be little or no resistance, indicating a full gas tank.
I think it would be fairly simple to create one of these at home using simple components from Radio Shack (a three position toggle switch, some leads, some resistors, and a box), but the magic question would be the value of the resistors.
Anybody own a tool C3826 or know what the resistor values should be? Would it be safe to get some ohm readings from a known good fuel tank sending unit and use these as the resistor values for E, F, and 1/2? It seems this would work since my 83 van service manual says you can substitute a fuel sending unit for tool C3826 in testing the fuel gauge if the special tool is not available. The same tool is also used to test the temp gauge and oil pressure gauge, so the same values as provided by the fuel sending unit should be correct for all gauges, yes? |
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bigslant6fan
Turbo Slant 6
Joined: 09 Aug 2008
Posts: 519
Location: Taneytown, MD
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Post subject:
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(Wed Sep 21, 2011 2:05 pm)
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8-10 ohms "full" ,75 ohms empty_________________ V8?? We don't need no stink'n V8!!  |
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Reed
Supercharged
Joined: 03 Nov 2002
Posts: 8515
Location: Fircrest, WA
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Post subject:
(Wed Sep 21, 2011 2:11 pm)
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| Ahh, thanks! I might make building one of these a back burner project. On the other hand, I suppose one could just use a fuel level sending unit for all tests instead of building a tool from scratch. |
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equium
1 BBL (New)
Joined: 17 May 2011
Posts: 9
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Post subject:
(Mon Mar 05, 2012 9:57 am)
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| I tested my sending unit on my workbench and I'm getting about 7ohms FULL and 70ohms EMPTY. The question: Is this an accurate test while the sending unit is out of the tank and on my bench?
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KBB_of_TMC
Turbo Slant 6
Joined: 09 Sep 2005
Posts: 848
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Post subject:
(Mon Mar 05, 2012 2:14 pm)
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| Some years ago, I made up my own testing tool w/ power resistors, a little plastic box, and some bananna plugs from Radio Shack; works fine.
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Red
Board Sponsor
Joined: 28 Oct 2002
Posts: 606
Location: Santa Cruz, CA
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Reed
Supercharged
Joined: 03 Nov 2002
Posts: 8515
Location: Fircrest, WA
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Post subject:
(Mon Mar 05, 2012 2:47 pm)
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Sweet. That is exactly what I was thinking of. I knew somebody had to have done this before!
I suggest that link become a sticky in the electrical forum. |
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DonPal
TBI Slant 6
Joined: 01 Sep 2006
Posts: 219
Location: Tolland, Ct. 06084
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Post subject:
Fuel Guage Testor
(Sat Mar 10, 2012 7:01 pm)
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I took all the info at the A body site & complied it into 1 annotated diagram assuming a sticky would rather pull up the gut info:
https://picasaweb.google.com/107913457502264904472/March102012#slideshow/5718451245205329426
I believe my 65 Dart has the voltage limiter built into a guage so verifying whether the limiter is effecting the results or the guage itself might be an added step?
My guage shows "overfill" when the tank is filled and shows 1/8 when I'm down only 6 gallons......with a new sending unit of questionable quality.....so this test might tell me if the new sending unit is not spot on?
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1965 Dart 75k, 225, 1920 holley/alum intake, 2 1/4 single exh., sbp manual scarebird front disc, 7 1/4 rear 2.94 sure grip, 14 x 4.5 OEM wheels, 833 OD with hyd. clutch, HEI, electric fan, ram air/heated air, Accusump. Goal-daily driver with good mpg.
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