Fuel sender Replacement

[MIPS]

Without dismantling the sender I can see through an opening it's designed the same as the original and uses a fine wire wrapped around a phenolic wafer with a brass slider contact. It's extremely well built. Given how the original lasted 40 years to my knowledge this one should be fine for the rest of the life of the car.

[86Woodgrain]

MIPS, where did you wind up buying the sending unit from? I'm also in Canada and my 86 wagon could use a new sender because my gauge is not accurate.

[MIPS]

MIPS, where did you wind up buying the sending unit from? I'm also in Canada and my 86 wagon could use a new sender because my gauge is not accurate.

From American Parts Depot as per, djm3452004 earlier in the thread.
Going back a few years in my posts it looks like this was recommended to me once before when I had to recalibrate my old sender.

As of this post I can see it's still listed as available on their website. P/N  936 1503J - $135usd

Be aware that it ended up costing me $60usd UPS shipping + $40cad in brokerage fees to get it here.......

[86Woodgrain]

Wow that's speedy. So probably around $285 CAD Wow. Well my gauge works but it's not accurate. Hmmm....

[MIPS]

Well the analysis on what happened to the old sender is done and it was the same problem that my other junk sender had.

I was in here before and had seen that the plastic grommet had cracked and this initially caused me calibration problems. I just reset it and hoped it didn't slip again. Unfortunately the slider contact even after being cleaned up and adjusted still developed a tiny hook on the end that snagged. Because it could now slip on the cracked grommet it was able to pull itself backwards until it shorted out against the wire just before the brass rivet (should be pretty close to 0 ohms resistance). That explains why at the end the gauge was mentally beating itself into the top of the dial. Finally it got itself in a position it could get tangled and snapped the wire.




I guess in this design its kinda unavoidable that eventually the slider is going to fail and ruin the sender mechanism but I guess 40 years isn't bad.

[Illeagle1984]

Anybody know anything about the wire that the slider contacts?  The wire broke on my other Eagle's sender, and if I can figure out how to rewind it I can save the cost of a new one.  Does the wire have a certain ohms/foot rating?  I may experiment with the ohm ratings provided.  It kinda looks like steel guitar string...

I have ideas to try and renew the contact on the slider arm, when it comes time.  We'll see if they work.

[djm3452004]

Anybody know anything about the wire that the slider contacts?  The wire broke on my other Eagle's sender, and if I can figure out how to rewind it I can save the cost of a new one.  Does the wire have a certain ohms/foot rating?  I may experiment with the ohm ratings provided.  It kinda looks like steel guitar string...

I have ideas to try and renew the contact on the slider arm, when it comes time.  We'll see if they work.

I'm assuming the whole thing is a kind of rheostat.  What throws me is the varying (increasing) length of the wire loops around the circuit board wafer as the wafer's width increases.  Typical rheostats I've played with are just sort of cylindrical with the same diameter of wire loops throughout.  Their function sort of intuitively makes sense to me.  This one with the varying wafer width and wire loop length increasing does not.

I can imagine that rewinding this would be difficult as it seems too easy to have (2) or more wire loops touch each other and "deaden" that section of the winding, i.e. no variable resistance for a given portion of the "sweep" of the contactor.

But I'm an industrial engineer, not an EE.... 

David

[Canoe]

... What throws me is the varying (increasing) length of the wire loops around the circuit board wafer as the wafer's width increases.  ...
I can imagine that rewinding this would be difficult as it seems too easy to have (2) or more wire loops touch each other and "deaden" that section of the winding, i.e. no variable resistance for a given portion of the "sweep" of the contactor...

But wait, there's more! 
- The movement of the float is not linear, but an arc.
- The movement of the sweep on the wires is not linear, but an arc.
- The spacing between wires is determined by the notches on the board. Using the correct diameter of wire, matching the inside curve of the wire to the board and sufficient tension, it would be hard to have wires touch. 
- The spacing between wires is greater on the board's narrow end, and less on the wide end.
- The sweep's contact likely touches more than one wire at a time.
 
The resulting R-delta is:
Full to 3/4, 34 ohms
3/4 to 1/2, 40 ohms
1/2 to 1/4, 46 ohms
1/4 to Empty, 97 ohms

The delta between deltas is: 6, 6, 51.

Without checking physical orientation, from the photo can you tell which end of the sweep arc is Full vs. Empty...

[djm3452004]

- The spacing between wires is determined by the notches on the board.

Ah!  I had not seen the notches in the wafer board initially, but in MIPS' photo, I can just make them out looking at it closer.

I would likely just get accused of throwing money at a problem, but I am not enamored enough with pulling my fuel tank for the 3rd time to risk me rebuilding something as finicky as a fuel sending unit.  In my book, that effort almost equates to pulling apart a 12V car battery to fix a bad connection between plates or something.  It's just not worth my time and effort to do that on a component that is so readily replaceable. 

But in an environment where something like a car battery ISN'T so easily replaced, you get this...
https://www.youtube.com/watch?v=sbRvXulcKAU&t=131s

Perhaps for the folks in Canada and elsewhere where shipment and "brokerage fees" (which I am thankfully ignorant of) really bump up the prices of simple items from the US, repair of something like a fuel sending unit is a more cost-effective (or perhaps satisfying) prospect.


Merry Christmas, All!

David

[Canoe]

...
I would likely just get accused of throwing money at a problem, ... It's just not worth my time and effort to do that on a component that is so readily replaceable. 
...  shipment and "brokerage fees" (which I am thankfully ignorant of) really bump up the prices of simple items from the US, ...

Those brokerage fees are just UPS b.s.. UPS looks at the item, its cost, where/who it's going to, and guesses how much ransom they can hold it for just for collecting the HST tax. If the destination is a business, look at double to triple the fees, or fees equal the cost of the item... That $114 headlamp assembly now has fees of $110, plus the HST tax. Save a lot of money by specifying a different carrier. USPS is the best. Many businesses in the U.S. have registered to collect and remit the HST to Canada, so they don't get Canadian buyers going to other businesses.

Shipping to Canada costs significantly more than shipping within the U.S.. I live an hour away from the border, so I get things shipped to a warehouse business in the U.S. border town, drive down, and bring it into Canada myself. Anyone can ship to a UPS store too, using any carrier. There's a $5 USD fee per parcel when you pickup. Much cheaper than shipping to Canada, even without the broker fees. Head down with a 1/4 tank of gas, fill up in the U.S. at lower prices, and after exchange and everything, the money saved on the gas pays for the trip down and back. Really miss being able to do that, since covid.

With fixing parts that can be bought? Depends on the price and availability of the part. I've learnt to keep a spare, or rebuild the old part I take off for use the next time it's needed. It's a lot easier to rebuild the old one you took off when you're not waiting on that to get it back together and running again. When I see something on sale that I'm going to need eventually, I grab it. Don't ask me how large my collection of stainless hose clamps is.

[MIPS]

I got a "mailbox" down in Everett that helps dodge import fees because when it's $20 to ship anywhere in the 49 states and $100 to ship an hour and a half North I'm gonna take the road trip route. Problem is for the last year and a half I've not been able to reach it (which sucks because my Carter EKE's down there), then after that nonsense briefly cleared up all the routes to the coast washed out last month. It could be another three or four months before I can finally step foot in the states again. x_x

[MIPS]

Hope yours last longer than mine did. I replaced mine for my SX/4 8 months ago. The resister in the new replacement eventually swelled and warped then shorted out against the housing causing a 3/4 tank indication all the time.

Didn't even last two years.
It started developing a condition where it would randomly shoot to 3/4 tank and then settle down again but then I had the car parked for a week while I was on vacation. I came back and immediately it was at 3/4 tank and would refuse to drop back down to where I knew the tank was.
Tank is coming out. Sender is getting inspected.

[MIPS]

Alright, tank's out and the sender is on the bench. Resistance confirms the fault is in the sender.
You are correct, the phenolic wafer the resistor is wrapped around is absorbing the fuel or tank moisture and it swells to the point it will touch the edge of the housing. Bad design.






The easiest fix would be to slip some sort of insulating material between the back of the resistor and the housing as the slider never touches the backside but eventually the excessive flexing of the arm will cause it to fatigue and break. Wedging something large behind it also risks if the wafer is still expanding the wafer to buckle and destroy itself against the sender arm. Same goes if you proactively do it before installing the sender.

Edited: I removed it and no, it will not go back to its regular shape if the end-to-end pressure is eliminated, so straightening it will not be that easy.

[MIPS]

[rmick]

Ya thats exactly what happened to my new sending unit. Trying to flex it back will defiantly break it and the windings will want to shift or break. Ask how I know. Might try some heat to see if it makes it flexible enough to straighten. I ended up gluing it back together so it was flatter and added some silicone under the board to support it from contacting the housing. Been good for a year now fingers crossed.