Series 2 1963 Fuel Tank Sending Unit

[loose_electron]

Hi all - Just measured the resistance of my sending unit in the fuel tank. (Sender is busted) This is the Series 2 tank that is sort of in the bottom of the trunk (errr... "boot" ) and holds 9 gallons, not the newer ones in the side rear body panels.

Anyhow... Looking around on the web, I ran across this sender which claims to be for the Series 2:

https://www.sportsandclassics.com/p...m-alpine-series-1-2-fuel-tank-sender-1046608/

Does anyone have any feedback on this web site, or the sender shown in the picture? It would be great to have a swap in sender in hand before draining the tank but have never gotten anything from this site before so am a wee bit skeptical.

Feedback appreciated!

Thanks,
Jerry

 

[loose_electron]

An additional piece of information - It looks like this sending unit was a Smiths part and got used in several other British cars:

https://www.sportsandclassics.com/part-type-subcategory/gas-tank-sending-units/

Still looking for feedback on anyone who has worked with this vendor-source.

tnx, Jerry

 

[Tom H]

Jerry,

Does it look like your old one? I am not familiar with this supplier, but he looks pretty legit. I see no other Sunbeam stuff in their listings, but if this was used on other LBCs that would explain why he has it.

Before discarding the old one, are you sure it's not just a ground issue? I have no experience with early series senders, but on later series the most common problem is getting the ground path completed through the pivot shaft. Some have solved the problem by adding a flexible ground wire to the pivot arm. You can find their fixes on this forum.

Tom

 

[65beam]

The sending unit was a Smiths unit. I sent the Harrington unit to Nissonger a couple months ago and they restored and tested it. A previous owner had broken the wire terminal off which required extra work and they also replaced the float. The repair includes supplying the gasket.

 

[DanR]

There are a few "other"Sunbeam items listed ... just do a search.

The item Jerry is asking about "looks' brand new! The Seller is located in CT,so as a suggestion find one of our Members from up that-a-way and see if they know of this outfit? If not perhaps maybe a member could pay them a visit for the benefit of us all!

One member in particular is Alpine 1789 (Our President of the SAOCA). There are a few others that might be available such as jsaiff, he may be the closest. Or boobtube ?

Our "new" Membership map we are considering will be a great help in such cases!

 

[loose_electron]

I have one ordered on speculation. Considering I have limited garage resources, in order to drain the tank and look at the original unit, I got to take the car to a shop. (draining and sloshing gas around where I live is a no no)

My sender shows a short to ground with a full tank, so the sender or an insulation point in the sender has failed. When I get the replacement unit I will be in a position to pull the original. If it fits, great, if not, I will fast fabricate a cover plate for the hole in the tank to get the car out of the shop running, while I send the original out for a rebuild.

Anybody suggest a gasket stock supply so I can hand cut a fresh gasket?

 

[Tom H]

Jerry,

So what does your gauge read when the tank is full? I know the Later series gauges and senders very well on a first hand basis , but all my knowledge about early series gauges is from discussions and data from others. Nevertheless ,from what I know about Series II gauges I am pretty sure that with a full tank, the sender resistance should be pretty close to zero. So if you measured "shorted", that's about correct for a full tank. If your gauge reads full always then maybe it is indeed shorted. But if it always reads empty, you have an "open" somewhere.

Tom Hayden

 

[65beam]

I have one ordered on speculation. Considering I have limited garage resources, in order to drain the tank and look at the original unit, I got to take the car to a shop. (draining and sloshing gas around where I live is a no no)

My sender shows a short to ground with a full tank, so the sender or an insulation point in the sender has failed. When I get the replacement unit I will be in a position to pull the original. If it fits, great, if not, I will fast fabricate a cover plate for the hole in the tank to get the car out of the shop running, while I send the original out for a rebuild.

Anybody suggest a gasket stock supply so I can hand cut a fresh gasket?

The gasket that came back with my rebuilt unit was cork.

 

[loose_electron]

Jerry,

So what does your gauge read when the tank is full? I know the Later series gauges and senders very well on a first hand basis , but all my knowledge about early series gauges is from discussions and data from others. Nevertheless ,from what I know about Series II gauges I am pretty sure that with a full tank, the sender resistance should be pretty close to zero. So if you measured "shorted", that's about correct for a full tank. If your gauge reads full always then maybe it is indeed shorted. But if it always reads empty, you have an "open" somewhere.

Tom Hayden

Tom:

Original gauges are 100% gone, the only original sending unit is the fuel tank sender, everything else is new stuff that supports the V6. The new gauges are Speedhut, and can be calibrated to whatever sender is on the other end. Measuring the sender in place with a full tank showed under 1.5 ohms, which indicates an insulation failure and short to the frame ground through the tank metal. (Call it an educated guess.)

It is my understanding that the sender when healthy ranges (roughly) from 30 to 250 ohms, depending on full to empty. With the new one I will measure and calibrate as part of the installation process.

As for the original gauges, it is my recollection that the older S2 used a Wheatstone bridge voltage division method and the newer devices S4 used current in a bimetallic strip for a slow thermal gradient change. Always kind of interesting to see how it was done before modern electronics took over.

Jerry

 

[loose_electron]

The gasket that came back with my rebuilt unit was cork.

Thanks, I got some cork stock ordered, hopefully the unit comes with a fresh gasket, if not I will have the needed material.

 

[Tom H]

Jerry, Where did you get the "30 to 250 Ohms" figure for a SII fuel sender? My information seems to indicate it's more like 0-100 ohms. In which case your existing sender may be fine. Did you ever measure it while the tank was at half or empty? You are correct about how the early and late gauges work. I'm still fascinated (and impressed) with how the older systems work. It's pretty hard to beat a Wheatstone bridge in terms of accuracy and stability but the bimetal seemed to actually have bettered some aspects in performance (and longevity!). But modern solutions obviously have a lot to offer in terms of production costs and flexibility.

You car looks fabulous! I just sent you an e-mail!

Tom

 

[loose_electron]

Jerry, Where did you get the "30 to 250 Ohms" figure for a SII fuel sender? My information seems to indicate it's more like 0-100 ohms. In which case your existing sender may be fine. Did you ever measure it while the tank was at half or empty? You are correct about how the early and late gauges work. I'm still fascinated (and impressed) with how the older systems work. It's pretty hard to beat a Wheatstone bridge in terms of accuracy and stability but the bimetal seemed to actually have bettered some aspects in performance (and longevity!). But modern solutions obviously have a lot to offer in terms of production costs and flexibility.

You car looks fabulous! I just sent you an e-mail!

Tom

Tom: I make my living in the world of electronics, and am pretty familiar with antique techniques that were used before the transistor came on the scene. And, yeah, I can design and fix vacuum tube stuff too.

The 30-250 number was from some discussions on this forum, I would have to go digging to find, but here someplace.

Anyhow - Let me cover the "why" of those gauge designs -

The Wheatstone bridge (WB) method used in the early Alpine meters was there because they did not have a quality voltage regulator at the time. The mechanical "sorta regulator" things that did exist were not terribly accurate, and really did not regulate anything but rather chopped by duty cycle switching. Since they could not get a steady voltage to work with, what they did instead was look at the difference between two resistive voltage dividers connected to the same not terribly well regulated voltage. Since the WB looks at the difference, a large amount of the error from the voltage source gets eliminated. These fuel gauges were 4 resistors, of which 1 of those resistors was the actual fuel sender. The other 3 resistors are embedded in the gauge itself.

https://en.wikipedia.org/wiki/Wheatstone_bridge

Thing about that WB setup was that it had a fairly quick response, and the fuel gauges do swing around as fuel sloshes around in the tank. There are tricks that can be used (low pass filter capacitors) to slow that down a bit, but it did not exist in the Alpine. Capacitors of the era would be needed and they were neither cheap nor reliable back then.

The newer S4 gauges used a bimetallic thermal strip with current running thru it in the actual gauge if I recall correctly. That bimetal strip is the same sort of thing they used in old fashioned house thermostats. In this case the heat in the strip is from current running in the strip, and the current is a function of where the fuel sender unit float is at. The time response of cooling heating is slower causing the gauge to respond slowly which is more suitable for a slowly emptying gas tank.

 

[Tom H]

Jerry, I know from our previous conversations that your experience and understanding of things like this. And I also understand them. I was simply my sharing my thoughts about how effective - though expensive- these earlier methods were.

My point about the value of the sender you measured is that it seems quite possible and even likely that your existing sender is fine. From my understanding, from several discussions with guys who had SII gauges, the sender should be about 0 ohms at full and about 100 ohms at empty. So your measure of "shorted" at full seems OK. Did you measure it at less than full?

Tom

 

[Toyanvil]

I have a ser II sender at home I will test, I will let you know tonight when I get home. On my Ser II I am running VDO gauges with the stock sending unit turned 180, if not full is empty and empty is full on the gauge.

 

[Tom H]

Toyanvil, So at least one brand of modern Fuel gauges reads low resistance as "empty". Interesting. Alpine stock gauges, both Temp and Fuel, are designed to read "low" when off or with little current (high resistance in sender) and "High or full" with lots of current ( low resistance in sender). Is there no way to change the way the VDO gauge reads? Does your VDO Temp gauge also read backwards?

 

[Barry]

The 30-250 number was from some discussions on this forum, I would have to go digging to find, but here someplace.

I have posted several times in the past that the "Stewart-Warner standard" for fuel level senders was widely used in the '60's and '70's. The standard resistance values were 240 ohms empty and 33 ohms full.

Within my ability to measure the actual resistance values, the fuel sender that came with my S-V very closely matches the S-W sender standard.

I recall reading that the early Alpines used fuel sender with different full / empty resistance values to work with the different fuel gauge mechanism (the Wheatstone Bridge design mentioned by loose-electron), but I do not recall the full / empty resistance values.

FWIW, 0 ohms empty / 90 ohms full is the standard for some modern senders / gauges.

Just my opinion, YMMV.

 

[Fordtootsie]

I am restoring a Ser I so everything is apart. I measured the ohms on my gas tank sender and found the following range.
18 ohms to 80 ohms

I have never driven the car as it is a project and I am still projecting so I don't know if the gauge system worked or not - But that is my 2 cents worth

John in Colorado

 

[Tom H]

John, Please confirm that the 18 ohms you read is at full and 80 ohms at empty.

 

[Fordtootsie]

OK I did some more measurements. The ohms readings go from 18 ohms which would be a full reading to 100 ohms which would be empty reading.

 

[Tom H]

Barry , I have done extensive testing with high precision instruments on three sets of SV gauges. There are 3 calibration dots on the face of SV gauges, at "0", "Mid scale", and "full scale", corresponding approx. to 50 deg or 0 gal, 85 deg or 4.5 gal, and 120 deg or 11 gal. The resistances required to hit these cal dots are 248 ohms, 77 ohms , and 28 0hms , which pretty well confirms your "S-W standard" information. And that also matches Jerry's "30-250" number. BUT again that is for later Series Alpines.

My info on early gauges is all second hand, but data taken by RootesRacer shows that the early TEMP gauges needed to get down to about 8 ohms for full scale reading, and nearly zero ohms would still show FULL. I am guessing that the Fuel gauge worked the same as the temp gauge and thus requires LOW resistance to read full. And John in Colorado just confirms that.

There is an on line article about these earlier type gauges, but it's about MGA Fuel gauges, and it looks like they worked opposite (high resistance indicates Full). The MGA gauges are also "upside down" from Alpine gauges with needles pointing down , but still with needle to the right indicating Full or Hot.

Do you know if modern gauges like Speedhut that Jerry is using can use either High or Low resistance to indicate Full?

Tom