Repairing fuel tank senders

[awg]

I have read all the tech posts and learned much, so I thought I might start with a contribution.

I have repaired several fuel tank senders on old vehicles and this can be done by the home restorer using only a soldering iron and ohmmeter.

Apart from mechanical problems, they often fail cause the internal wiring has gone open circuit.

Apply ohmeter to terminals, it should show 0-200 ohms roughly, if it shows open circuit, split the body of the sender carefully, usually by bending back the tabs.

You will see a wire wound coil and a slider that makes contact along the length of the coil...firstly, is the slider making contact with the coil?, breakage, mechanical deformation, or buildup of varnish may be preventing this.

Clean with methylated spirits. If the copper wound coil is very dirty use
1200 wet/dry paper and very carefully polish the coil.

If the coil has gone open circuit, it can be repaired. Usually it has broken from the end terminals. Use the ohmeter probe to slide along the coil with the other probe on a terminal. This should show a range of resistance that corresponds with the correct range.

If the coil has opened at the terminal you can see it.

To repair,obtain some very thin copper strands that roughly match the diameter of the broken stuff, easiest way is to rat some out of multi strand low voltage wire.

Now solder the new piece straight onto the broken wire end of the coil, the coil has to be slightly polished or the solder wont stick, it usually just blobs and looks a bit bodgy, but the ones I repaired are still going years later.

Next solder the other end onto the terminal!

This recompletes the circuit, check with ohmeter.

You may need tweezers and magnifying glass to help.

This repair may cause the resistance of the unit to change by 2 or 3%
but this is barely noticeable.

I made these repairs to vintage senders that were $200 to replace,
also on my CCKW.

The slider can also be soldered back onto its arm if it is broken and the wire wound core can be made serviceable by reinforcing with epoxy coated paper former stuck to the rear (non-slider side)

Please feel free to email me any time for clarification.

regards tony

[Chappers]

Another Nice tip Tony,I've got one which needs repair so I'll strip it and have a go.

Regards

Steve

[John V Cliche]

Thanks AWG
I have repaired mine the same way But I have never been able to explain the procedure as well as you just did.
If you do find one that is beyond repair Frank von Rosenstiel has NOS ones avail. for both CCKW fuel tanks as well as Chevy.
Thanks again
John

[sixbysix]

Hi Tony
a question relating to this old post.
My fuel gauge isn't working properly ... it only goes down to the halfway level. It was working back the front until a turned the arm around on the sender unit .... so now it reads 1/2 full when empty and full when full.

resistance across the sender unit - 13-14 ohms when empty , 32-34 ohms when full.