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MG MGA - Fuel gauge

I have my Smiths fuel gauge apart to restore the can. Inside is what looks to be a thermally operated gauge. There is a sping strip with insulated coil around it connected to the two terminals, I'm thinking it's a bi-metallic strip, and it's connected to the needle.
So this is not the magnetic type discussed on Barney's place. Is it compatible with the MGA tank sender?
Art Pearse

No. The MGB gauge works on entirely different principal, and the sender unit works in opposite direction from MGA, and in different resistance range. The MGA sender unit will be 0-ohms when empty, and about 70-ohms when full. The Smiths unit you have (if it is for later model MGB) will be something like 200-ohms empty and 90-ohms full (but not those exact numbers). It also needs a "voltage stabilizer" to supply an "average" 10-volts for input power.
Barney Gaylord

Hi Barney. I can't see the gauge resistance changing as it is a fixed coil.
Art Pearse

It is the sender unit resistance that changes. The earlier balanced magnetic field gauge needs lowest sender resistance (0-ohms) to read "E", 70-ohms to read "F". The later heater and bi-metallic strip gauge heeds highest sender resistance to read "E", lower resistance (but not 0-ohms) to read "F".
Barney Gaylord

So, do I need a new type sender?
I have a new Moss sender, but it is pretty bad and I think the empty is zero ohms. It is the same type as the old one that was too corroded. Maybe the PO mismatched them?

Art Pearse

If you want to use the Smiths fuel gauge, you need an MGB sender unit and a voltage stabilizer.
Barney Gaylord

Is the MGB sender a fit to the tank?
And does it work better?
Art Pearse

The sender unit for the Smiths thermal gauge does not fit directly in the MGA fuel tank.

Any fuel gauge can work when properly connected. There is a significant difference in the way they work. The magnetic gauge will waver in harmony with fuel sloshing in the tank. The thermal gauge has very slow motion for the needle.
Barney Gaylord

So, i have to make an adapter at the flange?
Art Pearse

If you decide to do this, take photos, make notes. You may be the first person to do it.
Barney Gaylord

Na, too much effort!
I think I will sell the gauge and buy the proper one.
Art Pearse

Am I right in assuming that the early MGB (Jaeger) gauges are compatible, despite having (different construction? and) lucar terminals? Reason I ask is that the DPO claimed to have fitted an MGB gauge to fix repeated problems. It certainly looks like an MGB gauge from the back and it works perfectly. The sender unit appears (from the outside) to be standard MGA.
Neil McG

I think the early MGB Jaeger gauge is magnetic, similar to MGA Jaeger gauge, and MGB may have Lucar terminals. I don't know if the sender units may or may not be in a compatible resistance range, but it wouldn't surprise me if so. Much of the early MGB is mechanically and electrically similar to MGA.
Barney Gaylord

I can confirm what Barney says: The early B unit is identical apart from having Lucar connectors.
dominic clancy

This thread was discussed between 10/09/2013 and 13/09/2013

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