NEW Gas Tank Sending Unit not working

[A383Wing]

found the company that rebuilds the OE bad sending units to as new condition and they work as they should

https://www.antiqueinstrument.com/

Bryan

[70 sublime]

I'm having a similar issue with a '56 Chevy BelAir that I just bought.  It has a standard gas tank sending unit (0-30 ohms).  The car has new Classic Instruments gauges (33 - 240 ohms).  Tanks, a company here in Iowa that sells reproduction gas tanks and sending units, also sells a MeterMatch.  It's an electronic device that allows you to match different gauges and senders.  You have 4 set points that allow you to match the dash gauge readings to the sending unit output.  I chose empty, 1/4, 1/2, and full for my settings.  It sells for $69.

Does something like that need to be reset every time the battery is un hooked in the car or does it remember the settings ?

[oldchevelle541]

To all , thanks again for excellent feedback. Glad to know I have options. Here is photo of original unit disassembled to see what the problem was.

[b5blue]

See how the winding's are on a tapered backing board. That varies resistance. (Save the parts.)

[Canadian1968]

exactly.......... kinda of what i said at the very start of this thread

The aftermarket plain and simple is not any where close how the orginal oem was made. It's not that that sendING unit does not work or is not grounded . It simply is not desineed / calibrated correctly for the b body gas tank .

The thread mentioned before https://www.forbbodiesonly.com/moparforum/threads/yet-another-fuel-gauge-thread-but-different.124786/

its a bit of reading but explains alot .

[oldchevelle541]

Received a reply from the company in Willoughby Ohio who rebuilds the original units. $175.00 to rebuild plus the ride. I will hang on to original and consider the service if my frustration with aftermarket continues. This is a company to keep in your files. They were quick to respond.

[A383Wing]

Received a reply from the company in Willoughby Ohio who rebuilds the original units. $175.00 to rebuild plus the ride. I will hang on to original and consider the service if my frustration with aftermarket continues. This is a company to keep in your files. They were quick to respond.

they are also quick turnaround time also....I have used them twice now

Bryan

[oldchevelle541]

okay - level of frustration starting to set in.

Purchased OEM grounding strap from Year One and got it installed correctly. Tight and connecting output line from sending unit to gas line on other side of rubber gas line. Gauge moves about 3/16" when key is turned on butwill not go past "E". Grounded tank to chassis - no change. Grounded sending unit to chassis in addition to Year One ground - no change. Under hold I noticed my negative battery cable is not grounded to radiator support so I used an alligator clip wire from post terminal to bolt on rad support - no change. Even though not the correct gauge I was looking for some added movement of the needle. Went back under car and with my new multimeter and re-measured OHMs on the new sending unit. Meter read 40 Ohms very quickly.

so what next ?

[70sixpkrt]

http://www.kramerauto.com

I bought mine from them about 3 years ago and it is still accurate. A buddy of mine bought one last year and it reads accurate still. They check the calibration and recalibrate it before they ship them out. Before I bought one from KramerAuto, I went thru 3 other vendors and none of them worked.

[Nacho-RT74]

40 ohms takes to a good sender. Its between the range maybe ready to give you in between 1/2 or 1/3 of the gauge reading? dunno

have you grounded the BLUE WIRE of the sender ? it should give you FULL reading on gauge. Disconect the plug and ground it!

[oldchevelle541]

Thanks for the question - yes I did ground it originally before I purchased the sender. I used an alligator clip wire to sender post and the other end to chassis turned the key and needle went to full. That was suggesting to me wire and gauge in dash was good. Negative battery cable does not have aux lead ground but video I have of car before leaving owner showed gauge working plus I see so many mopars on ebay without the aux ground wire and I bet their gauges work. I also learned that if your temp and oil pressure gauge work it should not be a cluster limiter or volt regulator in the dash. Since new sending is stainless do you think it grounds differently or does not ground the same as oem unit ?

[Nacho-RT74]

yeap is true, if any of the gauges work, problem is not on voltage limiter. Maybe gauge calibration itself, some pin loosen at PCB, wire broken between sender and cluster, but definitelly not the limiter.

but it's weird having 40 ohms and needle barelly moving.

SS vs OEM sender ?... well, I can't tell it. Stainless steel have a diff electrical coeficient transmission than regular steel, but is not something to worry. No like this at least

I think original sender is fixable, with some soldering gun and lead, overlaping the copper tab... or using an intermediate copper section between both. Just will need to readjust the angle between point and rheostat. It worths the try.

I already had tried being I'm overseas LOL. As somebody told somewhere... I allways have to think out of the box to fix my stuff on car because just the shipping kills me.

I in fact had a similar problem with my sender, but the tab got completelly loosed from the floater shaft, and lead doesn't hold the same between both materials, hence the reason they are electricaly welded, so never could get a nice fix. BUT I can see you can still get solded copper over copper with lead

[oldchevelle541]

Gents,
in addition to my comment above I want to disconnect lead wire to sending unit and if I am not mistaken should measure about 5 volts when key is turned on. This should also confirm limiter is in good order. If correct how do I connect wires from multimeter ? Red goes to end of dark blue wire but where do you suggest I hook up end of black ground wire ?  Chassis or sending unit ?

[oldchevelle541]

Yesterday I spent a good amount of time retracing my steps and I have decided to back away for awhile.
- pulled lead wire on sending unit and grounded it to chassis. Gauge needle went to full, check
- attached low voltage tester to lead wire, showed voltage going through but light was flashing not steady, not sure what this meant.
- attached multimeter to lead wire hoping to see about 5 volts. Meter would not steady out. May have not hooked it up correctly.
- attached new OEM ground at sending unit output to steel gas line other side of rubber hose.
- attached ground from gas tank to chassis
- installed new ground from negative battery post to radiator support. I see so many 1970 B Body Mopars with and without this aux ground.
- made other attempts to ground sending unit in different ways
- pulled kick panel under dash and did an inspection. Nothing looked out of sorts.
- as is when key turned on gauge needle moves 1/8" then stops
- all other gauges including temp works suggesting no problem with circuit board and regulator/limitator.

Although I am getting ohms reading out of the new sending unit I am beginning to think it and the original factory gauge are just not working together. It worked before car was delivered.

Like the old Model T's I will use a wooden stick to measure gas levels in the tank - more reliable. LOL.

[Nacho-RT74]

the voltage limiter is not a steady 5 volts reading, but pulsating signal which makes a 5 volts average. If you used a digital VOM won't get a clear reading. It can just tested by analog devices, analog VOM or test light, both going in and out at some speed rate.

( good one on the Model T gas tank check LOL )

hipothetically, check voltage on the gas sender lead agains ground doesn't work like that but just if there is some resistance failure around... check this vid

https://youtu.be/qdaOSiScEu8

however being the voltage limiter a pulsating signal I think will be a more complex reading to analize, specially being there is load being used on the rest of gauges ( after check the vid, will understand this statement ).

why don't try to check the sender out of the tank ?... ground it with a wire and conect it to the sender lead... move the floater.

or on the bench with the VOM on Ohms.

[b5blue]

The connector pins on the printed circuit board for gauges is a known possible trouble spot. I soldered the base of the pins to the board VERY carefully.     

[jlatessa]

B5 has it right, be careful the solder does not hang down under the board,
it can short out against something, but I can't remember what.
It's been a long time and old age has had it's toll!

Joe

[oldchevelle541]

Thanks all will check your comments out.  BTW I did try to look up behind the dash and looks pretty original, does not look like anyone has been in there. I am considering getting my original sending unit rebuilt. Wouldn't that be a hoot to plug that one back in after rebuilding and it works.

[Nacho-RT74]

even B5 has it right, gauge, wiring, plugs and terminals are checking good when grounding the fuel sender wire, so I seriouslly doubt that is the problem and I THINK there is something weird about the sender. thats why I would test it out of the tank

[oldchevelle541]

Just got my new gas gauge LOL. No wires, ground cables, or anything.

[oldchevelle541]

just watched video suggested by Nacho - good stuff. Will check reading on each side of sender. I have new ground on other side of sender and if I measure any volts then we have localized problem. Still thinking I am leaning towards junking that new Classic Industries sender.

[Nacho-RT74]

being a pulsating signal and limiter still getting load on the other gauges can't tell if you get some easy to read signal at VOM reading voltage. Even less being a digital VOM ( in this case )

Just got my new gas gauge LOL. No wires, ground cables, or anything.

LOL

[A383Wing]

just watched video suggested by Nacho - good stuff. Will check reading on each side of sender. I have new ground on other side of sender and if I measure any volts then we have localized problem. Still thinking I am leaning towards junking that new Classic Industries sender.

we tried three senders from them, every one was junk

Bryan

[oldchevelle541]

Tried to test for voltage and grounds again tonight - still cannot find anything abnormal or obvious. The factory original is getting boxed up and sent out tomorrow to be refurbished. If I don't need it I will keep it for the other '70 Mopar we have in the family which still has it's original. Never know when they go. 

[oldchevelle541]

To all,
will let you know how we make out but I wish to extend my sincere appreciation for all the helpful comments. I got rid of a 2016 Dodge Challenger R/T 392 for this Coronet because you can't work on the new ones. I like old cars that have character and personality but this problem has me stumped.