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EBody Fuel Gage Question #354835
06/22/09 06:27 PM 06/22/09 06:27 PM
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Just put new 3/8"" sending unit in my 70 Challenger 440RT. Have it out of the tank and checking it out--can only get 1/2 tank reading on gage when float is fully extended. When I ground out the blue wire, I get full gage deflection. I have a good ground on the sending unit. Any suggestions? I hate to rip into the dash (cuz I just put it all back together ) Any suggestions on what my options would be will be appreciated
Re: EBody Fuel Gage Question [Re: 70VERT] #354836
06/22/09 06:38 PM 06/22/09 06:38 PM
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If you get full deflection when you ground the blue wire, then your gage and wiring are good. Some of the re-pop sending units are not of the best quality

While outside on the turnpike They got this new hit tune Where thrills become as cheap as gas And gas as cheap as thrills
Re: EBody Fuel Gage Question [Re: Hrtbkr] #354837
06/22/09 07:22 PM 06/22/09 07:22 PM
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yeah I know what you mean but this is the 2nd unit I've installed and both do the same thing (actually I am getting a little more deflection form the one I have in there now)
Re: EBody Fuel Gage Question [Re: 70VERT] #354838
06/22/09 08:16 PM 06/22/09 08:16 PM
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what I was kinda wondering if there isn't some way to get the gage to read full scale with the current signal from the sending unit?? Seems I remember some post about adding a resistor or something. Just spent 120 bucks for the unit from mancini and I'm kinda stuck
Re: EBody Fuel Gage Question [Re: 70VERT] #354839
06/22/09 11:15 PM 06/22/09 11:15 PM
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As said from the sending unit forward you are fine. I would run a long jumper wire w alligator clips from the sending unit ground to batt negative & make sure you have a complete circuit.

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Re: EBody Fuel Gage Question [Re: 70VERT] #354840
06/22/09 11:16 PM 06/22/09 11:16 PM
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I wired a reostat in parallel with my sending unit. More resistance=less voltage. It's still not perfect but it's usable

While outside on the turnpike They got this new hit tune Where thrills become as cheap as gas And gas as cheap as thrills
Re: EBody Fuel Gage Question [Re: Hrtbkr] #354841
06/23/09 03:59 PM 06/23/09 03:59 PM
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where would I install the reostat? Does gage function normally with it? Thanks
Re: EBody Fuel Gage Question [Re: 70VERT] #354842
06/23/09 04:29 PM 06/23/09 04:29 PM
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I wouldn't think an added rheostat would fix that much error(gauge shows 1/2 tank @ full deflection). If the gauge is grounded well I'd think it is the wrong unit

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Re: EBody Fuel Gage Question [Re: RapidRobert] #354843
06/23/09 04:56 PM 06/23/09 04:56 PM
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u can check with an ohm meter for the range..
Re: EBody Fuel Gage Question [Re: AARCONV] #354844
06/23/09 10:00 PM 06/23/09 10:00 PM
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OK--I ran a solid wire from the neg battery terminal to the sending unit---when I touch it to blue wire get full gage deflection, when hooked up to sending unit with blue wire on sending unit terminal, get 1/2 deflection on gage. This is a 3/8" sending unit with a rally gage. I get the same result with 2 different sending units. What am I missing here??????
Re: EBody Fuel Gage Question [Re: 70VERT] #354845
06/23/09 10:13 PM 06/23/09 10:13 PM
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With the long jumper wire from the batt neg post clip it to the flat metal on the sending unit to make SURE the sending unit has a good ground and that a poor ground is not causing this malfunction then with the sending unit hot lead from the front plugged into the nub on the sending unit raise the float & see what you get on the gas gauge.

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Re: EBody Fuel Gage Question [Re: 70VERT] #354846
06/23/09 10:13 PM 06/23/09 10:13 PM

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will your ballist resistor affect your signal?Are you getting a good chassie ground?
Re: EBody Fuel Gage Question #354847
06/23/09 10:19 PM 06/23/09 10:19 PM
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Yes--I ran a ground wire directly from the neg terminal of the battery to the sending unit to be sure I had a good ground connection
Re: EBody Fuel Gage Question [Re: 70VERT] #354848
06/23/09 10:26 PM 06/23/09 10:26 PM
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Quote:

OK--I ran a solid wire from the neg battery terminal to the sending unit---when I touch it to blue wire get full gage deflection, when hooked up to sending unit with blue wire on sending unit terminal, get 1/2 deflection on gage. This is a 3/8" sending unit with a rally gage. I get the same result with 2 different sending units. What am I missing here??????



Do you have an ohm meter?
The sender is just a rheostat that is adjusted by the float level. If the float is all the way up, the resistance should be very low, just a few ohms, just like when you short it out with ground wire. Disconnect the sender from the circuit and measure the resistance from the blue wire to frame ground. No voltage should be present or it will mess up your meter.
It is unlikely that two senders are bad but it also is not impossible. If you have the original, measure it just for kicks too.
Craig

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Re: EBody Fuel Gage Question [Re: denfireguy] #354849
06/23/09 10:34 PM 06/23/09 10:34 PM
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Craig--I want to make sure I have this right---are you saying measure teh resistance from the blue wire itself to ground or from the sending unit's stud (where blue wire attaches) to ground? What kind of reading should I be looking for?
\
Re: EBody Fuel Gage Question [Re: 70VERT] #354850
06/23/09 11:12 PM 06/23/09 11:12 PM
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Quote:

measure teh resistance from the sending unit's stud (where blue wire attaches) to ground? What kind of reading should I be looking for?

nothing connected to the sending unit measure ohms from the stud to the round flat metal on the sending unit(ground) iirc 10 and 80 ohms with the arm "up" and "down". I might be off on the 2 figures but post what you get then disconnect the ohmmeter and plug in the blue lead to the stud and with the circular metal flat grounded directly to the battery neg what does that give you on the gas gauge w key on & you moving the arm thru its travel?

live every 24 hour block of time like it's your last day on earth
Re: EBody Fuel Gage Question [Re: RapidRobert] #354851
06/24/09 04:54 PM 06/24/09 04:54 PM
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OK--here's the scoop with my "cheapo" voltometer---with sender disconnected, moving the arm from up to down get about 14-55ohms. With blue wire connected and battery ground on sending unit gage goes form empty to 1/2 full with float travel from up to down. I get about the same results with the other sending unit in both cases. Whaddya think?
Re: EBody Fuel Gage Question [Re: 70VERT] #354852
06/24/09 06:42 PM 06/24/09 06:42 PM
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oh yeah--just for info-- I am using a Year One reproduction wiring harness also (not sure that this matters but thought I'd mention)
Re: EBody Fuel Gage Question [Re: 70VERT] #354853
06/24/09 06:46 PM 06/24/09 06:46 PM
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Challenger 1 Offline
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Quote:

OK--here's the scoop with my "cheapo" voltometer---with sender disconnected, moving the arm from up to down get about 14-55ohms. With blue wire connected and battery ground on sending unit gage goes form empty to 1/2 full with float travel from up to down. I get about the same results with the other sending unit in both cases. Whaddya think?



According to my FSM, you should have 9.6 ohms plus or minis 1 ohm at full stop. At empty you should have about 73 ohms plus or minis 17 ohms.

Maybe you can bend the stops to get the right readings?

If you can't get those readings the manuel says to replace the sending unit. You sure you have the right sending unit?

Last edited by Challenger 1; 06/24/09 06:51 PM.
Re: EBody Fuel Gage Question [Re: Challenger 1] #354854
06/24/09 07:50 PM 06/24/09 07:50 PM
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kinda hard to say--my car is cloned and really nothing is original. I am using a 3/8" sending unit with a new tank and my fuel gage is on a rally dash. Thought all this should work together (???)
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