11 replies to this topic

[TheJack]

So on my smith speedo the voltage regulator is missing an arm, just wondered if this would be a good replacement as I don't want to order a new one and it not be the right one

 

http://www.ebay.co.u...=item461eb442fa

 

and do I need positive or negative earth?

 

[KernowCooper]

Depends if your car is a very early car and positive earth or a later car and negative earth ? what car are we talking about?

[TheJack]

Depends if your car is a very early car and positive earth or a later car and negative earth ? what car are we talking about?

Well I have a 1990 rover mini but I have a smith clock to put into it, have all the cables but I noticed one of the arms of the regulator has snapped off

[KernowCooper]

Yours will be a negative earth car

[TheJack]

Yours will be a negative earth car

But any voltage regulator would work that is negative? 

[KernowCooper]

The Voltage regulators used on the centre speedo cars with negative earth were 12v regulators with a 9v output

[dklawson]

The OEM type stabilizers are electromechanical and not polarity sensitive.  They chop the voltage on and off and deliver an "average" 10V to the gauges.  The Caerbont unit in the link above does not mention polarity so it is probably still electromechanical.  Modern solid-state replacements are polarity sensitive.  If your car was built after about 1970... it will be negative earth.

[Dusky]

The Voltage regulators used on the centre speedo cars with negative earth were 12v regulators with a 9v output

So If you mounted a fuel gauge without the stabilizer ( on centre clocks)

then it would constantly read full?

[KernowCooper]

No read higher that what the reading actually was. eg: half a tank might read 3/4 or you run out on 1/4 ?

[dklawson]

Also, running a bimetallic (post 1964) gauge system without the voltage stabilizer will allow excess current to flow through the gauge and sending unit which will reduce the life of both.

[tmsmini]

What would the opposite condition cause the gauge to read?

In my case, I have an early 64 Traveller that had a speedo swap when I purchased it. I do not remember if I connected the stabilser or if it was already connected. I recently learned that the sender/gauge is the early non-stabilsed type.

Terry

[dklawson]

You cannot mix the two gauge systems.  The pre-stabilizer gauges operate on full system voltage but their senders change resistance in the opposite direction and have a different resistance range.  When you mix the components you will always have a gauge that reads "backwards" showing low fuel when the tank is full and a increasing fuel level as you drive.

 

On your traveler, try and measure the sending unit resistance.  If it goes from about 270 Ohms = empty to 30 Ohms = full, you need the later fuel gauge with the stabilizer.  If the sending unit measures about 10 Ohms = empty to about 90 Ohms = Full, you have an early sending unit and you need to use the early gauge without the voltage stabilizer.

 

That being said, you can add a component (or two) to the system to make it work.  Visit Spiyda Design and look at their Wizard product.  It is supposed to adapt any sender to any gauge.  However, if you are using the later bimetallic fuel gauge you will also need to use a voltage stabilizer to the circuit to protect it from excess current.

https://www.spiyda.c...lectronics.html