The early and later gauges are pretty easy to tell apart.  If the gauge has a skinny needle that bounces around easily and snaps up to a reading when the key is turned to the run position, it's an early gauge used w/o the stabilizer.  If the gauge needle is broad and rises slowly when the key is turned to the run position, it's a bimetallic (later) gauge used with the voltage stabilizer.  From the back the gauges look different also.  On the back of an early gauge you'll find a couple of male spades.  In addition to that you will find a pair of nuts mounted in slots.  On the later gauges you will have a couple of spade lugs and there will be some open holes with slots in them OR the holes on the back will be covered/closed with some tiny cork disks.

Thanks Doug. I may now know why the system in the one car was not accurate. I have an older sender as I got about 8-85 ohms.

The gauge was connected to the voltage stabilzer when I got it and I left it that way the past 10 years. I wonder which gauge I have.

Terry

The easiest way to identify a sending unit vintage is to connect a multimeter to its terminals and move the float arm through its full range of motion.  The following values are nominal and yours will not match exactly.  If the meter shows a range of 10 to 90 Ohms you have an early sender which is used with the magnetic gauge (no voltage stabilizer).  If you measure a resistance range of 30 Ohms to about 250 Ohms the sender is for the later bimetallic gauge system that uses the voltage stabilizer.   You can see that the resistance ranges are very different.  The resistance values also change in opposite directions (10 Ohms Empty to 90 Ohms Full vs 250 Ohms Empty to 30 Ohms Full).  Again... the resistance values I listed are ballpark figures not firm and exact values.

According to Somerford there are only two for LWB cars.

My sender has about 75 degrees of sweep and the numbers look like FT 530, but it is hard to tell.

PS: I just noticed it says 12V on it, does that mean it is a non-stabilized sender?

Chuck can probably tell you about the senders for the LWB cars, I cannot.  I know that the LWB senders are physically different from the sedan senders but electrically I have always understool they had the same resistance range as the sedans.  The sedan did have 3 senders with a short-lived transitional unit being used briefly in 1964.

Hi Terry, I guess I just stumbled onto dumb luck.  My sender is bolt in and is perfectly compatible with the stabilised gauge so it must be the second type....  Not sure what you mean by the "design OK " but sender arm not swinging properly??

Anyway, before I installed the tank I cleaned it and the sender mechanism and it now works prefectly.   I used to keep mileage records (and a small stick - and a spare tin of fuel.. but now i just look at the gauge....

Cheers, Ian

Ian:

I am trying to find the documentation for the gauge changes in the LWB cars.

I thought maybe it was in Doug's article:

//www.minimania.com/pdFile/SmithsVoltageStabilizer.pdf

Although the article is mostly about the voltage stabilzer, there is other information.

I thought there were three type of senders for the LWB, early non-voltage stabilzed, volatge stabilized bolt-in and voltage stabilized bayonet-in. I may have that information wrong as I am not able to find where I read that.

I don't think the problem is with the design, but with the ability to have the float arm swing evenly within the confines of an LWB tank. I should have a variable resistor with the range that Doug mentions so I can mimic the resistor in the sender. I will just need to calibrate it from 30 to 270 by marking it.

Terry

I don't think there's any inherent design problem; mine works fine... 

Some time ago I replaced the tank in my S.  I was given a NOS fuel gauge (ie 10V stabilised) to match the bayonet style sender in the new (well, replacemetn) tank and all was fine.  Later, I installed the instrument pod in my Traveller but of course the gauge was not compatible with the original Traveller sender.

Fast forward to replacement Traveller tank (out of a later model van)

... And surprise surprise..despite the "new" tank having a bolt in sensor (which looks excatly the same as the (incompatible) one installed in the old tank) it works perfectly with the 10V gauge....

Maybe it was the earth all along????  Are the LWB tanks with bayonet style senders - or are they all bolt in???

Cheers, Ian

There are some tests you can make.  Visit Radio Shack (or a friend who tinkers in electronics).  Get a few 1/2 Watt resistors.  You want a couple around 30 Ohms, a couple between 240 and 270 Ohms, and a couple somewhere near 150 Ohms.  With the ignition on, disconnect the green/black wire from the sending unit and insert the wire from one end of the 30 Ohm resistor.  Hold the other wire on the resistor against ground and watch the gauge.  Within a minute the gauge should go to full.  Replace the 30 Ohm resistor with the 150 Ohm one and again, hold the other resistor wire to ground.  This time the gauge should read about 1/2.  Finally repeat the test with the 240 to 270 Ohm resistor.  The gauge should read empty but the needle should not be off (below) the very bottom of the scale.  If you find these readings, the gauge is OK and the problem is with the sender and/or its ground.  Clean all the terminals and try a new ground wire/connection first as those are cheaper than a new sending unit.

BIG AL

I know with the shape of the LWB fuel tanks that the senders have a hard time giving an accurate reading. Is there anything that can be done with all the equipment out of the car to get a better reading?

It appears both our LWB cars use the voltage stabilized gauge with the appropriate sender even though they are in the window for the other gauge and sender(1964- early 1965)

The gauge in one car only reads half full when full, but that may be a physical issue with the resistor in the sender. It was not used for a while and after six months it is now consistently moving between empty and 1/2. I have replaced the voltage stabilser with an electronic version.

The other car has everything out of the car so I can mock up and test everything.

Terry