gas tank & gauge help

[Mgicm]

Hi
put in a new tank and gauges in my 50 ad. having an issue. Gas gauge reads 0-30 ohms. Tank sender is 0-90 ohms. I need to put a resistor inline to make up the difference. Gauge reads 3/4 at empty and runs up. I need more resistance to drag the needle down.

Any idea how to do or where to get parts? Not sure exactly what is needed.

thanks!

[dwcsr]

This is one option

http://www.tanksinc.com/index.cfm/pa...rod/prd473.htm

you could also get a variable 50 ohm resistor or what they call a POT. the resistance you need is 45 ohm to make it work. so deal it into 45

Don't know where you can get the POT , google it

[Second Series]

There may be a problem with the ground at the tank. The gauge should read empty when the sender is at 0 ohms. I would check that first. To make the 90 ohm sender read half (45 ohm), connect a 90 ohm resistor across it, not in series. To make it 30 ohm you could use a 47 ohm resistor across the 90 ohm sender. This is a simple fix that will get the gauge to read empty when the tank is empty, and full when the tank is full however the transition between full and empty may not be even. It may read 3/4 longer than it reads 1/4 for example.

[e015475]

The solution that DWCSR shows a link to is the only one I know that will work well without modifying the tank or sender

Whether you use a fixed resistor or variable resister, it matters not - the gauge will only be correct when the tank is full or empty and very unlinear between the two. A pot will allow you to fine tune it a bit at full, but not much else

If you use the resistor - fixed or pot, here's how your gauge will read-

Tank is empty, gauge reads empty (so far so good)

Tank is a quarter full, gauge reads half full

Tank is half full, gauge reads three-quarters full

Tank is three quarters full. gauge reads 90% full

Tank is full, gauge reads full (back on track!)

There are several other options - all fall into the category of 'science projects'.

-There are several micro-processor based solutions on the net, including some with Arduinos. (this has the potential to keep me sidetracked for at least a couple months)
-A simple transistor arrangement can be used to vary the current to the gauge proportional to the input from the tank sender.

I'm not savvy enough for either of these two solutions, and I want my gauge to be accurate, so I'm going to modify my tank to add another 0-30 ohm universal sender and abandon the 0-90 ohm. A universal tank sender is about $35 from Summit. I'll have to cut another hole in my tank but I've not put any gas in it yet, so at least I don't have to dry it out.

The universal 30 ohm sender seems to be the best solution with the least amount of clap-trap and dollars.

[mr48chev]

This one fits the stock tank and is 30 ohms https://www.classicparts.com/1947-53...ctinfo/23-523/

If you swapped tanks what about looking at the 30 ohm universal sender and seeing if you can adapt it to the tank unit that is now 90 ohm? The big issue there would be how the wiring connected and if you could make that work safely.

My personal experience with cutting the hole in the tank and drilling the holes for the screws and hoping everything would seal real good hasn't been the best.

[e015475]

It seems like all the earlier GM tank senders had a five hole mounting flange that uses a cork gasket to seal. The later 90 ohm senders install with an oring and a retaining ring.

The holy grail here would be a 30 ohm sender on the later oring flange. I can't find such an animal . If anybody has I'd sure like to hear about it.

I'm pretty goosey about modifying something that carries electricity and operates inside a fuel tank. Tanks Inc has an the flanges I'll need to have a good shot at a leak free installation