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Mon Oct 20, 2025 6:17 am

I guess if it operates correctly I won't care where it's made.

Mon Oct 20, 2025 8:40 am

baldessariclan wrote:

Final shots are of the sender w/ arm at upper extreme position (about 6 ohms resistance), and the corresponding fuel gauge needle reading at or above the “full” point, once again as would be expected:

Note that the float is now above the mount. It will not get to that position in the tank as it will hit the top of the tank.

Byas

Mon Oct 20, 2025 8:48 am

Yes, and I was told that the ohms testing should be performed on a stand at the same stance that would recreate the position of the sender base on the tank. BUT, I don't know if that's true or if it makes a difference. My guess would be it doesn't matter.

Mon Oct 20, 2025 8:51 am

bnam wrote: Note that the float is now above the mount. It will not get to that position in the tank as it will hit the top of the tank.
Agreed. Although it's also worth noting that the top of sender body/flange is mounted a bit lower than top of tank where float will contact. So top of float will always be above top of the sender body/flange when gas tank is full -- just not quite as far as shown in the pic above.

It's been my experience that the fuel gauge needle usually comes right about to middle or upper edge of the "full" (1/1) line when my tank is completely full, which would be more-or-less "as expected" IMO, given the observations & discussion above.

Thu Oct 23, 2025 4:43 pm

Well, my “good” VDO unit came and, yes, it was made in India. It tested good with 73.4 ohms and 4.3 ohms. Big problem: If you go back to my “report” on the previous page, this new VDO is doing the same thing on a dry run.

Gauge and/or vibrator?? Or do I just go back to filling up every 200 miles?

Thu Oct 23, 2025 4:53 pm

I reread your report. My money is on the gauge itself.

Have you checked that you are getting the correct voltage out of the vibrator? I believe thats 5v

Thu Oct 23, 2025 5:23 pm

That’s my next move. I have tomorrow off with decent weather.

My wive LOVES being a bug widow.

Thu Oct 23, 2025 5:49 pm

bugger-off wrote:
My wive LOVES being a bug widow.

Not sure how to take that.

1. You are being facetious and she is upset that you are spending time on the car
2. She's happy that you are out of the house and leaving her in peace.

:D

Thu Oct 23, 2025 5:57 pm

talljordan wrote: I reread your report. My money is on the gauge itself.

Have you checked that you are getting the correct voltage out of the vibrator? I believe thats 5v

If the vibrator is working correctly the voltage should be pulsating and not steady.

Thu Oct 23, 2025 6:05 pm

viiking wrote: bugger-off wrote:
My wive LOVES being a bug widow.

Not sure how to take that.

1. You are being facetious and she is upset that you are spending time on the car
2. She's happy that you are out of the house and leaving her in peace.

:D

I guess it’s whatever mood she’s in!

Thu Oct 23, 2025 6:08 pm

The only other thing I can think of before you do too much else is to actually measure the resistance being received at the meter.

It appears you have done a great job measuring with a combination of rulers in the tank and the resultant resistance. Not knowing how you did this but I assume you never reinstalled the meter along with the grounds every time you changed the level in the tank? It would be ideal if you could reproduce the "real life" situation.

It would just be simple to at least measure the resistance at the fuel sender with the wiring disconnected and compare that to the end of line resistance being received at the meter when it is connected. At least that way you can discount any resistance issues with the wiring.

Thu Oct 23, 2025 6:21 pm

bugger-off wrote: Well, my “good” VDO unit came and, yes, it was made in India. It tested good with 73.4 ohms and 4.3 ohms. Big problem: If you go back to my “report” on the previous page, this new VDO is doing the same thing on a dry run.

Gauge and/or vibrator?? Or do I just go back to filling up every 200 miles?

Give me a few weeks and I have a solution for you that will replace the vibrator and you can align the sender levels to the gauge.

Thu Oct 23, 2025 6:29 pm

Would suggest/request you take and post some pictures similar to those I did earlier — i.e. show us where your sender’s arm is sitting when the gauge is reading at the full line (1/1), 1/2 line, 1/4 line, & R-line. Plus maybe also what your gauge is showing when the sender arm is up against the upper and lower stops as well.

I can do likewise w/ my spare sender and the fuel gauge in my car — might help give you a better feel for if maybe it’s actually the gauge that’s out of tolerance and/or going bad, rather than the sender.

Fri Oct 24, 2025 8:14 am

Yes, I can run the testing again with pics and get them posted.

Fri Oct 24, 2025 11:52 am

Ok, here are the readings I’m getting with that spare NOS VDO sender I’ve got. I obtained it a few years ago from a Samba classifieds seller, IIRC — it’s probably 1990’s or later production, I’m guessing (?).

Here’s the sender arm position and resistance reading when the fuel gauge is reading “1/1”:

Sender arm position and resistance reading when the gauge shows “1/2”:

Sender arm position and resistance reading when gauge shows “1/4”:

Sender arm position and resistance reading when gauge needle is on the “R” line:

Fri Oct 24, 2025 12:10 pm

I decided to also dig out and test the old original sender that was on my car when I bought it. The male electrical connector tab had been bent up and partially cracked by a PO. I babied it along for a couple years, but it eventually broke off completely — ugh. :-(

So I did a rough fix by drilling a shallow hole next to the tab base and gluing a wire in there, and that worked for a few more years — until it started cutting out sporadically, and I decided to source and obtain a new sender.

Anyway, I cleaned that old sender up, re-glued the wire in hole, and here are the readings I got with it:

Here is the sender arm position and resistance reading when the fuel gauge is showing “1/1”:

Sender arm position and resistance reading when gauge shows “1/2”:

Sender arm position and resistance when gauge shows “1/4”:

Sender arm position and resistance when gauge needle is on the “R” line:

Here’s the resistance reading and gauge needle position when the sender arm is resting on the lower stop (tank “empty” -?):

Note that it’s been my experience that the fuel gauge in my car seems to read reasonably accurately — i.e. when the needle is on “1/2”, it usually takes 5-6 gallons to fill the tank; needle on “1/4” takes about 8 gallons to refill; and needle in “R” zone usually requires 9 to 9-1/2 gallons to refill.

I’ve never run it down to completely empty, but on one occasion got the needle down near the far left “point” of the “R” (reserve) zone triangle, and it took about 10 gallons to refill on that occasion…

Fri Oct 24, 2025 1:05 pm

Wow, man! Thanks for all the hard work testing and posting pics. I have yet to run my tests but your’s look incredibly close to my previous results.

What really throws me off is the 1/4 tank reading when the float is down just a couple inches! Is that normal? Am I being unrealistic that the gauge would ever read 3/4 full for any period of time?

Another thing is that my arm bottoms out when the tank is a quarter full. Because of the tabs, or “stops”, on the base the arm/float don’t come close to moving any further down with the actual fuel level in the tank.

Fri Oct 24, 2025 4:25 pm

To baldessariclan.

That has to be one of the best and most complete descriptions of how something works. Clear, concise, fact based and scientific.

I think those photos and the description warrant a "how it works" sticky for others to understand how it works. It absolutely shows the non-linear level change with float angle change and how it corresponds to my photo of the change in winding turns inside the wiring.

Well done! =D> =D> =D> =D>

Sat Oct 25, 2025 9:40 am

bugger-off wrote: ... arm bottoms out when the tank is a quarter full. Because of the tabs ...
Those tabs are easily bendable, so you can adjust them to fit your tank configuration.

Sat Oct 25, 2025 4:36 pm

Inclement weather today with no garage space available. Hopefully tomorrow.