Fuel gauage sending unit

[jimainnj]

Has any one used the JC Whiney universal fuel sending unit in there P15 Ply

JcW Can't tell me if it has 2 wire conections, I put in a unit from Roberts in June it worked for a couple of days, and I just keep putting in gas till I had time to test. I just tested it for ohm's and got none

Roberts said it should have 10 to 90 ohms, the only way they will take it back is

if I remove the sending unit and the dash fuel gauge so they can test.

What do ya think about this?

[Norm's Coupe]

I believe the JC Whitney unit is a one wire setup. Are you sure you have a good ground on your gauge and sender. If not, it won't work properly, or not work at all. Try running another good ground to the sender from the frame or bumper. If it works, run a permanent ground wire to the frame. If that doesn't work, check the connection at the gauge. Make sure it's good and tight and has a star washer on it to supply a good clean ground. If it still doesn't work right run new wires from the sender to the gauge outside the car temporarily. If the gauge works then, your old wires are probably shot. So, move the new wires inside the car and make them permanent.

[jimainnj]

If there is no ohms reading at the sending unit (with the wires disconected) wouldn't that tell me the sending unit is bad? I did use star washers on the gauge when I worked on the system and they are tight.

[Plymouthy Adams]

first step is defining the exact unit in question..your profile states 47 so unit should be the 2 wire sender..there will be three wires posts on the guage..one is power..one is sender #1 and other is sender #2 wires this must hook in exact position on the sender..(1-1 2-2) the sender itself will have two wire terminal..reading between 1 and 2 (these are marked) with an ohm meter is a constant 30 ohms.. the float lever has a wiper on the lever inside the body that takes the resistor to ground though the sender body/tank mount..(why ground is critical) the wiper grounds the two wires at the same time to the common ground..the total resistance is is split between each wire to ground relative to the wipers position..most all the senders I have seen in the past are corroded inside at the point where the wipers pivoting contact touches the metal body of the sender body..quick test with the meter will take any one terminal on the sender from 0-30 when read to ground..removing the sender is necessary to reading the smooth operation of the wiper contact across the face of the resistor wiring and of the wiper ground to body point itself..if erratic or break in continunity in testing will result in one or theother if not both wires opeing the path and errors in the amound of gas reproted to non functioning completely

this will aid you in trouble shooting when installed and electrically connected..

[jimainnj]

If there is no ohms reading at the sending unit (with the wires disconected) wouldn't that tell me the sending unit is bad? I did use star washers on the gauge when I worked on the system and they are tight.

I forgot to mention I tested the wires too the sending unit there is 6 volt's on the wires that connect the sending unit.

[jimainnj]

Tim there is no ohms reading on the sending unit with the wires disconected and the unit still in the tank. If the sending unit is good wouldn't there be an ohms reading?

[Plymouthy Adams]

I forgot to mention I tested the wires too the sending unit there is 6 volt's on the wires that connect the sending unit.

if you do not have the 30 ohms across the terminals 1 and 2 of the sender the resistor is open..sporatic reding at best depending on the float arm position each side of the break..guage could then register a very incaccurate reading..(relative to the break on the wire wound resistor)

[jimainnj]

There was no movement of the fuel gauge, if I remove the sening unit and move the arm up and down should I get and ohms reading enen though I don't get one while its in the tank? could the unit be stuck, I just can't see a good reason th send the gauge and the sender back together if its just the sender

[Plymouthy Adams]

if the wire is broken somewhere along the way...(obvious by not reading 1-2) then yes the wiper could pick up a resistance reading to ground but it will be only on one contact or the other...IF you do not have the 30 ohms across the two terminals though the other tests are moot..as the unit will never read or indicate properly..the ystem is such it pulls the needle in both directions at the same time by the split resistance and is the reason for the stable guage even in a sloshing gas tank..the built in 5 volt regualtor adds to this stability..the dampening of the meter makes the guage so slow to respond usually it take 3-5 regulator cycles to even out the indicator..

[jimainnj]

Thanks Tim I pulled the dash gauge and the tank sender out and packed them up,

I will send them back to Roberts as they required. Jim

[Norm's Coupe]

I don't know.........but I don't think I'd send them my gauge since I did not buy that from them. Sounds like they want to test the gauge to see if it's OK. But..........you've already done that. They should have their own gauge to test the sender with. I'd also be worried about the gauge getting lost or damaged in all that shipping back and forth.

Since you already have both out, you can test both on the bench with a 6 volt battery and jumper wires. Hook up the sender to the gauge with jumper wires. Then add another jumper as a ground from the sender to the gauge. Then move the arm of the sender slowly up and down to see if it works. If the gauge does not work then, it's probably the sender. If it does work, you had a bad wire or ground when they were in the car. Keep the gauge sitting upright as it would in the car when testing.

About the only thing that can go wrong with gauge is the points get worn or dirty. It's unlikely the spring is bad. So.......prior to making your test, run some paper between the points to clean them off.

[jimainnj]

Norm the gauge did not work, the sender is bad, the points look good, and the only way they would repalce the sender was for me to send both, I know it,s not a good idea but its that or buy another sender. I bought a lot of insurance for the parts. Thanks Jim