Previous Thread
Next Thread
Print Thread
Ebody sending unit wrong resistance value. #1691977
10/29/14 05:19 PM
10/29/14 05:19 PM
Joined: May 2008
Posts: 958
eastern, pa.
C
cudabitten Offline OP
super stock
cudabitten  Offline OP
super stock
C

Joined: May 2008
Posts: 958
eastern, pa.
I installed a new sending unit and filled up with about 6 gallons of gas. I have no reading on the fuel gauge. I grounded the wire at the sending unit and the fuel gauge goes to full. I measure 190 ohms between the sending unit and ground. I read that the sending unit should be something like 9 ohms to 90 ohms. I'm guessing mine is 33 to 240.
If this is correct, does anyone know how to fix this? All I can think of is adding a resistor in parallel with the sending unit, or increasing the voltage.
If I add a resistor in parallel, I do not think the gauge reading will be linear.

Re: Ebody sending unit wrong resistance value. [Re: cudabitten] #1691978
10/29/14 05:30 PM
10/29/14 05:30 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
R
RapidRobert Offline
Circle Track
RapidRobert  Offline
Circle Track
R

Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
make a long wire with alligator clips on each end & 1 end on the batt neg post and scrape other end on sender flat circular metal & see if you have continuity all the way up front. You wouldn't wanna increase voltage. A parallel circuit would not reduce voltage (think of Nacho's bulkhead parallel bypass or visualize the drive around lanes on either side of the main checkpoint at a border crossing. You'd wanna resistor in series (in the blue wire if we're on the same page) but I think it'd be a nightmare of experimentation to get the right resistor but I dont know electronics so no firsthand experience. I kept my 5/16 sender which worked fine & soldered in a bung in the bottom of the tank for enough flow for my app (my adv was I had a new Spectra tank). EDIT on second thought a resistor in the blue line to ground WOULD reduce voltage that the sender sees

Last edited by RapidRobert; 10/29/14 05:39 PM.

live every 24 hour block of time like it's your last day on earth
Re: Ebody sending unit wrong resistance value. [Re: RapidRobert] #1691979
10/29/14 06:04 PM
10/29/14 06:04 PM
Joined: May 2008
Posts: 958
eastern, pa.
C
cudabitten Offline OP
super stock
cudabitten  Offline OP
super stock
C

Joined: May 2008
Posts: 958
eastern, pa.
Thanks, I also have a Spectra tank. And Yes, if I hook up a resistor in parallel with the sending unit, it will decrease resistance.So if I have a 240 ohm sending unit, and I place a 240 fixed resistor across it, it will decrease my resistance by one half. I just dont think as the float travels, it will be a linear reading on the gauge. I guess if this doesn't work, I replace the new sending unit.

Re: Ebody sending unit wrong resistance value. [Re: cudabitten] #1691980
10/29/14 06:15 PM
10/29/14 06:15 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
R
RapidRobert Offline
Circle Track
RapidRobert  Offline
Circle Track
R

Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
I've heard nothing but bad regarding aftermarket sending units. You might talk to an electronics whiz. A guy directed me to call a guy at the local Radio Shack (on an unrelated issue) who is sharp on that stuff. A similar plan might work for you but I gotta feeling that it'll be alot of experimenting ahead of you. Holler how it (all) turns out. EDIT If I had my druthers I'd want it dead on at the lower end of the scale as I dont like hitchhiking

Last edited by RapidRobert; 10/29/14 06:17 PM.

live every 24 hour block of time like it's your last day on earth
Re: Ebody sending unit wrong resistance value. [Re: RapidRobert] #1691981
10/29/14 06:37 PM
10/29/14 06:37 PM
Joined: May 2008
Posts: 958
eastern, pa.
C
cudabitten Offline OP
super stock
cudabitten  Offline OP
super stock
C

Joined: May 2008
Posts: 958
eastern, pa.
Funny, I went out to the garage to double check ground to battery neg,=(0.5 ohms), and I thought the same thing, if i'm going to add a resistor, I would want the "e" side to more accurate. I'll let you know.

Re: Ebody sending unit wrong resistance value. [Re: cudabitten] #1691982
10/29/14 07:38 PM
10/29/14 07:38 PM
Joined: Feb 2012
Posts: 4,443
Morristown Tn.
7
71birdJ68 Offline
master
71birdJ68  Offline
master
7

Joined: Feb 2012
Posts: 4,443
Morristown Tn.
Dixie has sending units made by the original vender, send that one back, and get the real thing from them.

Re: Ebody sending unit wrong resistance value. [Re: 71birdJ68] #1691983
10/29/14 10:46 PM
10/29/14 10:46 PM
Joined: Jan 2004
Posts: 755
Tempe, AZ
L
loco340cuda Offline
super stock
loco340cuda  Offline
super stock
L

Joined: Jan 2004
Posts: 755
Tempe, AZ
If the resistance is changing with the fuel level (assuming a linear resistance change) and you add a fixed resistance in parallel to this variable resistance then the combined resistance will be non-linear.


70 Cuda 340 4 speed - now stroked to 416ci (SOLD)
2017 Mustang Shelby GT350
Re: Ebody sending unit wrong resistance value. [Re: loco340cuda] #1691984
10/29/14 10:49 PM
10/29/14 10:49 PM
Joined: Dec 2008
Posts: 1,323
Virginia's Eastern Shore
D
dmoore Offline
pro stock
dmoore  Offline
pro stock
D

Joined: Dec 2008
Posts: 1,323
Virginia's Eastern Shore
Don't buy that China crap...call these guys.....www.tristarradiator.com

Re: Ebody sending unit wrong resistance value. [Re: 71birdJ68] #1691985
10/30/14 12:08 PM
10/30/14 12:08 PM
Joined: Jun 2008
Posts: 1,822
Colorado
D
denfireguy Offline
top fuel
denfireguy  Offline
top fuel
D

Joined: Jun 2008
Posts: 1,822
Colorado
Quote:

Dixie has sending units made by the original vender, send that one back, and get the real thing from them.


That is what I would do as well for two reasons:
1) to get an accurate reading
2) Support someone who has gone to the trouble of trying to supply good stuff to the hobby.

As for being linear with a resistor in parallel, none of the 70s era Mopars I owned were terribly linear from the factory. Either the gauge plummeted to half tank and then took longer to get to empty or they took forever to get to half tank and then plummeted from there. You just have to get to know your gauge and what it means. The factory on in the Cuda never did go to full when it was filled and it still has a couple of gallons in it when it says empty, which is good.
Craig


2014 Ram 1500 Laramie, 73 Cuda
Previous mopars: 62 Valiant, 65 Fury III, 68 Fury III, 72 Satellite, 74 Satellite, 89 Acclaim, 98 Caravan, 2003 Durango
Only previous Non-Mopar: Schwinn Tornado
Re: Ebody sending unit wrong resistance value. [Re: denfireguy] #1691986
10/30/14 12:49 PM
10/30/14 12:49 PM
Joined: Nov 2003
Posts: 12,493
Western Colorado High Desert
moparmarks Offline
I Live Here
moparmarks  Offline
I Live Here

Joined: Nov 2003
Posts: 12,493
Western Colorado High Desert
I've been going through the same thing. Just got a Mancini unit and it reads 9-84ohms. Going to install it today and hope it works.
Dixie just shows the 5/16" unit and I need a 3/8" with 1/4" return.


72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, .
Moparmarks Parts & Restorations
Desert Mopar Metal
Grand Jct. CO
970-261-7039
http://moparmark.com/
motormangj@gmail.com
Re: Ebody sending unit wrong resistance value. [Re: moparmarks] #1691987
10/30/14 10:33 PM
10/30/14 10:33 PM
Joined: May 2008
Posts: 958
eastern, pa.
C
cudabitten Offline OP
super stock
cudabitten  Offline OP
super stock
C

Joined: May 2008
Posts: 958
eastern, pa.
I will consider the two venders listed here in this thread.
I never even thought about the resistance value when I bought this unit over a year ago.
My fault, I listened to someone, not here, about going to a 3/8 line instead of the factory 5/16. I'm thinking that is where I went wrong. I also had to adapt the carb end. My application is on a 74 cuda. One of the only things I bought wrong for the restore though, so I'm ok.

Last edited by cudabitten; 10/30/14 10:45 PM.
Re: Ebody sending unit wrong resistance value. [Re: cudabitten] #1872901
07/18/15 02:39 PM
07/18/15 02:39 PM
Joined: May 2008
Posts: 958
eastern, pa.
C
cudabitten Offline OP
super stock
cudabitten  Offline OP
super stock
C

Joined: May 2008
Posts: 958
eastern, pa.
I just wanted to update this post. I finally got my restore on the road last month and after driving for a bit noticed that my fuel gauge was reading almost half tank, which was correct. But then when I looked down again it was empty so I figured the sending unit resistance value is correct. I removed the unit last week and took it apart and found that the part that "wipes" along the windings, had too much tension on it and was stuck. I made two adjustments, one was decreasing the tension on that part, the other was bending the tab that the arm rests on so the wiper would always be in contact with the windings. I've been driving it around now, and it works perfect.
This is a Spectra unit and it is made very nice compared to the original one I removed.

Re: Ebody sending unit wrong resistance value. [Re: cudabitten] #1872905
07/18/15 02:50 PM
07/18/15 02:50 PM
Joined: Aug 2007
Posts: 566
WA
T
tman Offline
mopar
tman  Offline
mopar
T

Joined: Aug 2007
Posts: 566
WA
Good to know it works good. Is this the one with plastic or brass float?

Re: Ebody sending unit wrong resistance value. [Re: tman] #1873114
07/18/15 07:36 PM
07/18/15 07:36 PM
Joined: May 2008
Posts: 958
eastern, pa.
C
cudabitten Offline OP
super stock
cudabitten  Offline OP
super stock
C

Joined: May 2008
Posts: 958
eastern, pa.
Brass.







Powered by UBB.threads™ PHP Forum Software 7.7.1