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MG MGB Technical - voltage stabilizer

i have a 64 mgb roadster. the voltage stabilizer is missing. could anyone please help me with the correct connections. thanks
vignes

Up to chassis number 48756 in Oct 1964 they didn't have a stabiliser.

From then they did, with Smiths instruments instead of Jaeger, and an electronic tach instead of a rev counter. The fuel gauge system is completely different at both the gauge and sender and the two systems can't be mixed.

Shouldn't be able to go wrong with the later type as one terminal should be a male spade and the other a female so you can't get them mixed up. Green and light-green/green are the colours. The most important thing is to get a good electrical connection where the mounting tab is screwed to the firewall as this is part of the circuit. Without that the fuel gauge will read high.
Paul Hunt 2

thanks paul
my chassis number is53843 and it does come with smith gauges. is the absence of the voltage stablizer responsible for my tacho swinging erratically on driving , and a faulty reading on my fuel gauge. its shows 1/4 tank when its full. i have changed the sender unit from moss.
vignes
vignes

Vignes - The tach does not get it's voltage through the voltage stabailzer and the fuel gauge reading 1/4 when the tank is full is not the result of a missing voltage stabalizer, rather it would fluctuate as the engine rpm incerases or decreases. You can get a wiring diagram for your car from Advanced Auto Wire at: http://www.advanceautowire.com/ that will show how the stabalizer is wired. Just click on stock schematics, then on MGB and scroll to the year of your car. You can print the diagram out to make it easy to use. Cheers - Dave
David DuBois

after inserting the float and tapping it in place, a possible result is to have the float arm at an angle . . . you may even have to do some bending yourself to get it right. On mine, usually after about an eon, enough fuel has seeped into the float to drag it down.
Dan Robinson

As David says the tach does not use the stabiliser. Tach swinging about can be caused by ignition LT problems, although these usually cause a misfire as well. Also loose connections on the 12v and ground supplies to the tach, or dry joints/bad connections inside the tach.

A missing stabiliser would cause a less than E reading on the fuel gauge, unless it has been bypassed i.e. the green and light-green/green wires connected together, which would mean the gauge would read high.

With the ignition on connect a good ground to the green/black at the tank while watching the gauge. the gauge should move smartly up to above Full. Don't leave this ground connected for longer than you need to as it drives a bigger current through the gauge than is normally the case.

If it shows F, then when you have a full tank connect the good ground to a cleaned bit on the body of the sender. If it goes up now then the sender ground is bad, it goes to a number plate bolt in the boot. If it still shows 1/4 then connect the clean bit of the body of the sender to the green/black. If it goes up now the sender is faulty. When buying a sender always check that it moves smoothly through its full arc, roughness indicates the wiper may be catching on turns of the resistance wire which will cut through them very quickly. Before fitting it to the tank connect the green/black and black wires to it and with the ignition on make sure it moves the gauge from E (or thereabouts) to F (or thereabouts). As long as it does that then go ahead and install it, and check the calibration afterwards, the gauges usually need tweaking when a new sender is installed.

If with the ground on the green/black it still shows 1/4 find where the green/black from the rear harness joins the one in the main harness with a 2-way bullet connector by the fusebox, and test there also, both sides. If it goes up now there is a bad connection either in that connector or at the tank.

If it still shows 1/4 do the same on the back of the gauge. If it goes up now there is a bad connection at the gauge or the connector by the fusebox.

If it is still 1/4 check the voltage on the light-green/green while the ground is on the green/black at the gauge. Without a stabiliser it should be a steady 12v, with a stabiliser it should be switching between 12v and 0v about once per second. Less than 12v (when it is on) indicates a bad connection back towards the fusebox. 12v indicates a bad gauge.
Paul Hunt 2

hi david dan and paul . thanks for the info. will try and sort out my fuel gauge problem this weekend. thanks a million
vignes

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This thread was discussed between 09/10/2007 and 18/10/2007

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