petrol and temp gauge wiring

[DickB]

I have looked at the wiring diagrams. Cant make head nor tail of them. Probably as the wiring is not the same as in my vehicle - 11 owners and some home improvements i guess.

Trying to get the gauges to work proper like. So, the fuel sender is connected to the gauge, correct? And the gauge is connected to the live via a fuse box? and the temp gauge is connected to a live feed and the other connector to the temp sender???

So if this is the case (which it might not be), can the live feed for both gauges be wired in tandem to the fuse box/battery? both gauges work but the fuel sender now just says half full/empty all of the time. The temp gage can be random according to which wires are connected. When earthing it directly from the gauge it went into the red. And the fuel gauge when earthed directly went to full. Neither are connected to the light/ignition switch. I am guessing they are attached to a red kill switch , that acts as the ignition as this is when they activate (or not). Help.

[Wittsend]

We need to establish just what you have.
A temp and fuel Gauge suggest a post April '67 model.
A picture of your instrument cluster will help.
We then need to see the top of your fuel tank sender - it should look something like this:-



The voltage stabiliser is connected to A4 on the fuse block. This is an ignition on controlled 12V supply. To test your wiring loom - you can simply run a wire from A4 to the voltage stabiliser direct. If the instruments work you have found where the fault is. If nothing then read below.....

The "fly" in the ointment is the voltage stabiliser. A little metal can behind the dash panel that produces a constant 10V to drive the water temp and fuel gauges.



If both instruments are wired correctly and still not working the chances are the voltage stabiliser is broken. They are quite cheap, the OE electromechanical can, can be replaced with a solid-state electronic device for little money - look on eBay under "MG voltage stabiliser".

[DickB]

I have a 66 swb but has a 17h 2.5 90 petrol engine in it. Dash , as you say is not the original either. The fuel and temp gauge have two connectors on them each. The only thing behind the dash (apart from the wires) is the indicator switch/unit.

[DickB]

Now I re call, there is a unit that is in the centre of behind the dash that is secured to the body of the vehicle, but nothing is wired into it. I will take some pics and post them when I get home.

[Wittsend]

Need pictures of the gauges ...

Your vehicle would have left the factory with an ammeter and a fuel gauge. Both instruments would have had arrow shaped gauge pointers.

The water temp gauge was a feature of the post April 1967 chassis suffix D and onwards late 2As. They had a straight gauge pointer.

The worst thing is when POs mess around and mix-&-match early and late instruments.
A 1966 vehicle would not have had a voltage stabiliser and the tank sender would look something like this:-



Looks totally different to the late 2A tank sender I posted above ^^^

To complete the circuit, no matter which type of tank sender you have the tank sender needs to be earthed to the chassis nearby.
Trap an earth wire under one of the sender fixing screws and drill a hole in the chassis for a self tapper screw. Scrape the chassis back to bare metal.

 

[DickB]

Thanks. Not sure the picture has come through though.

[DickB]

it has now. Must be my PC.

[DickB]

how do i insert a photo?

[Craig T]

Press the reply button under this post, don't use the quick reply window at the bottom of the page.
Image options all appear then.

Craig.

[Wittsend]

Look in the "All about the Club & this Forum" section right at the top of the forum - There's a "How to" topic there.

[DickB]

Hopefully you can see the pictures. This is the wiring for the temp and fuel gauge. It looks like the wiring is correct. I only get the fuel gauge to move if i do a jump wire from the spade terminal to earth. It goes to the top as if full. When removed it returns to zero. Is it the sender in that case?I have traced two wires to the tank sender and one leads to an earth and the other to the voltage regulator. Unfortunately, the wires are mostly red, so a tad confusing.

[Alan Drover]

More than likely it's the sender. Try Emberton Imperial for a replacement. Theirs are better quality.

[Wittsend]

OK ... the good news is that you have a late 2A instrument pod with a voltage stabiliser and the correct tank sender.

It might be the tank sender that is kaput - but first check you have a good tank sender to chassis earthing - as I posted ^^^ earlier.

Does the water temp gauge work - I can't remember what you posted ^^^.
If the water temp gauge is working properly then the voltage stabiliser  is OK.
If not ... replace the voltage stabiliser.

Still no joy, then replace the tank sender.

I wouldn't go straight in and play with the tank sender, as you'll disturb the seal and maybe have the complication of a leak between the sender and tank.


 

[Craig T]

Only the Diesel senders have two terminals on them, one for the gauge and one for the low fuel warning light.
The sender does not have an earth cable, it is grounded through the tank.

Maybe you have the sender wire going to the low level switch terminal instead?

Craig.

[Wittsend]

Following up on Craig's reply - the picture is not good but it seems your tank sender has 2 terminals = a diesel sender. The 2nd terminal is for a low fuel warning light. You don't want to run dry with a diesel as it's a right pain bleeding the fuel system at the side of the road on a cold, wet winter's night.

I believe that tank senders are now "generic" you get the 2 terminals, your choice if you use the low fuel. And they have an adjustable float so they can fit the tanks of many other British cars. This means suppliers only have to stock one part.

You can not rely on the tank being earthed. You need to have a dedicated earthing wire as I posted ^^^
Note, these generic tank senders now have a dedicated earthing terminal. On early senders you have to make your own earthing arrangements.



If you look carefully at the tank sender's surface near the terminals you'll see they are stamped either with a "T" or "W"

T = tank = fuel level gauge
W = warning = low fuel warning light