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72 Gas tank sending unit impedence values

Forum: C3 Electrical, Body and Interior

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72 Gas tank sending unit impedence values

Posted: 11/9/06 1:28pmMessage 1 of 5
w
windrider1200
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Clifton, NJ - USA
Joined: 10/3/2003
Posts: 142
Vette(s): 1972 Coupe Ontario Orange Black leather interior LS-5; Turbo 400

Anyone know what the range ( empty to full ) of impedence is for a 72 gas tank sending unit?

BB NJ Ken

1972 T Top 454; "Boomer" Latest "upgrades": 1 1/8" front Stabilizer bar. Rebuilt SS calipers with O-ring pistons. Under car Chambered exhaust. Fiberglass rear spring (360lbs/in). Bilstein Rear Shocks. 3/4" Rear Stabilizer Bar. Tow hitch. Performer manifold with 600 cfm Holley. Comp Cam 262 .499 lift. L-88 Hood in process

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72 Gas tank sending unit impedence values

Posted: 11/9/06 8:19pmMessage 2 of 5
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Adams' Apple
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
Uh...low to high? LOL
 
This is a question I don't think I've ever heard! So...I went & checked the service manual...no luck...it says to "test with a known good unit"(sender)!!!  Confused 
 
If you have a multi-meter set to ohms, it should have a full sweep, from infinity to 0, I would think. I've never actually checked the resistance numbers...just that it makes a full sweep.
 
Are you having problems with your gauge?

Joel Adams
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72 Gas tank sending unit impedence values

Posted: 11/10/06 7:36amMessage 3 of 5
w
windrider1200
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Clifton, NJ - USA
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Vette(s): 1972 Coupe Ontario Orange Black leather interior LS-5; Turbo 400
Not really. I'm getting ready to order some aftermarket gauges to replace the factory ones. The oil press gauge doesn't work, and I find ammeters much less informative than voltmeters. Anyway,  the gauge bezel in my car now is cracked at the usual place,  it will need replacement eventually. So, for the time being, I don't mind hacking up the old one for aftermarket gauges and a DIN radio.  I'm looking at the Z series Autoguage line. 

1972 T Top 454; "Boomer" Latest "upgrades": 1 1/8" front Stabilizer bar. Rebuilt SS calipers with O-ring pistons. Under car Chambered exhaust. Fiberglass rear spring (360lbs/in). Bilstein Rear Shocks. 3/4" Rear Stabilizer Bar. Tow hitch. Performer manifold with 600 cfm Holley. Comp Cam 262 .499 lift. L-88 Hood in process

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72 Gas tank sending unit impedence values

Posted: 11/14/06 5:22amMessage 4 of 5
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luft 1
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Mesquite, NV - USA
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Vette(s): 82
About your gas sending unit the ohms are as follows 0 ohms=empty... full tank ohms reading 84-88 ohms= full. And then of course what ever between those reading is what is left in the tank. With the guage wire disconnected it should slowly go to full, with grounded should read empty, just to verfy correct guage operation.
Steve.
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72 Gas tank sending unit impedence values

Posted: 11/23/06 6:53pmMessage 5 of 5
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kstyer
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Vette(s): 1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!
Those are good numbers.
 
And an open circuit will cause the gauge to read above full.  You can go to Radio Shack and get a range of resistors to test the gauge reading.
Or short the wire to the tank, get a zero reading, leave it open and have the gauge go past full, and then put a test light in line and read somwhere between 1/4 and 3/4 tank, depending on the test light.
 
If it passes those test, put in a sending unit,  If it responds but won't operate as described, repair the gauge or check for high resistance in the wires.  
You can repeat these test at the gauge itself to eliminate the wires.   Now if there is a good power and ground to the gauge and the resistances still won't make it operate correctly, replace the gauge.
 
Don't forget to make sure the sending unit has a good ground before doing anything else.   A bad ground is a very common problem.
kstyer2006-11-23 18:54:30
On the "Tail of the Dragon"
(some day, no strike that, October 2008 it turned red, still in progress!)

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