TR2/3/3A fuel sender

[TFB]

My fuel sender reads 4.5 ohms ,empty,at the sender regardless of float position.Are these units serviceable?Who has the best replacement sender units post 60k tank?Thanks Tom

 

[CJD]

You're saying it never changes from 4.5 ohms as you rotate the float arm?

 

[TFB]

You're saying it never changes from 4.5 ohms as you rotate the float arm?

Yes,while I move the float with a wire hook the reading doesnt change. Tom

 

[TR3driver]

I would be giving the hairy eyeball to the connections on the top. The sender might possibly have shorted internally, but it seems very unlikely. Inside, it is basically a wire-wound resistor, and a lever attached to the float arm shorts out part of the resistor.

But the terminal on the top (at least on earlier units) is just a screw through a hole with a phenolic or nylon "top hat" bushing to keep it from contacting the sides of the hole. If the bushing were broken or absent, the screw or nut could be shorting to the mounting plate.

If that isn't it, there is at least some chance you could open it up, find and fix the problem. It is a very simple device.

Sorry, no recommendation for a replacement. I've never had to replace one.

 

[Simmo]

From my testing It seems that the resistance should be 0 - 100 Ohms. Empty to full.

 

[TexasKnucklehead]

I assume you removed the wire to the gage, or better, from the sender, before you did your tests? Perhaps you have a shorted wire or gage.

 

[TFB]

I assume you removed the wire to the gage, or better, from the sender, before you did your tests? Perhaps you have a shorted wire or gage.

Thanks for all the replies.First test in tank was with wires to sender disconnected.I removed sender and it tested 4-81 ohms out of the car.Looking at the terminals one stud is larger so I thought this must be for a reason so I switchited wires to have 12v from gauge on small stud,with the phenolic washer and it all works now.So either for some reason the sender is polarity sensitive or I got lucky. Thanks Tom

 

[martx-5]

If you do need a replacement fuel sending unit, be wary of what's out there. I bought a unit from Moss awile back that fit the tank OK, but gave bogus readings because the design was not right. I bought one from a guy on ebay whose sender more closely matched the original, but had it's little problems also, however, they are easily rectified making the ebay sender useful.

I have it documented in the thread linked to below along with a pic of the three senders...the original, the Moss unit and the one from ebay.

https://www.britishcarforum.com/bcf...-Sender-From-Moss&highlight=fuel+gauge+sender


Edit: I see you got it sorted out while I was typing, but for anyone needing a replacement sender, be careful of what's out there.

 

[Jerry]

Bought mine from Rimmer Brothers and it is the most accurate sender/gauge I have ever had in a British Car . Must have got lucky.
Jerry
TR3A

 

[6TTR3A]

I've had good luck with the NOS units, although they do vary a few ohms from unit to unit. Some 3-98 ohms, others 5-95 ohms. I don't consider that a big deal since the Smiths design is far from perfect to begin with. I think it is best to calibrate your sending unit with your gauge on the bench to get the best reading. There is probably someone in your club or in your are that can help you if you need.
Frank

 

[dklawson]

Calibration of the gauges used before the voltage stabilizer was added is well described on Barney Gaylord's MGA Guru web site. The system is the same.

Start at the link below to get a general understanding, then read forward several pages as he goes over calibrating both with resistors and with your sending unit.
https://mgaguru.com/mgtech/electric/fg_01.htm

 

[TR3driver]

Calibration of the gauges used before the voltage stabilizer was added is well described on Barney Gaylord's MGA Guru web site. The system is the same.

Start at the link below to get a general understanding, then read forward several pages as he goes over calibrating both with resistors and with your sending unit.
https://mgaguru.com/mgtech/electric/fg_01.htm

But don't forget that the resistances are not quite the same. You need to adjust Barney's numbers to match the TR sender.

 

[dklawson]

Agreed. I prefer to calibrate a gauge to the sending unit it will be used with rather than match it to fixed resistance values.