8 replies to this topic

[Wiggywithahailo]

So I have established that my temperature gauge works but I have no fuel gauge or interior light I have a pulsing at both interior light and at the fuel tank wires also has a new sender unit
Any ideas would be much appreciated
Thanks Mark

[Kieranlee999]

a loose connection on the live end could cause this. Check what it is like on the fuse box (Third one down if it is the standard 4 glass fuse one) 

[Wiggywithahailo]

Thanks Kieran Ill av another look

[dklawson]

So I have established that my temperature gauge works but I have no fuel gauge or interior light

I have a pulsing at both interior light and at the fuel tank wires also has a new sender unit

 

How do you know the temperature gauge works?

What is "a pulsing"?  Do you mean that measuring the voltage you see its value bouncing up and down?

 

After 1964 the fuel and temperature gauges are powered by a single voltage stabilizer.  The voltage stabilizer was an external component on the back of the gauge cluster for Smiths instruments.  On the later Nippon Seiki gauges the stabilizer is "built in" to one of the two gauges.

 

What gauge type do you have?  What year is your Mini?

[Wiggywithahailo]

Hi the car is running so tempreture gauge climbs gradually yes it bounces as a reading on both interior light and fuel gauge wires
Car is a '91 mini 1000 with two clock dash

[dklawson]

Were I you, I would check other points around the car (virtually anything) to see if other circuits display this same "bouncing" of the voltage readings.  While the sending unit wire MAY have an observable pulse due to the operation of the voltage stabilizer... the interior light circuit has nothing to do with that and should be "stable".  If the pulsing occurs on other circuits and you are confident that your meter is in good shape, this suggests an alternator problem.

 

Regardless, the sending unit wire will have a pulse on it due to the way the voltage stabilizer works... not all meters can observe it.  As mentioned the voltage stabilizer powers both the electric fuel and temperature gauges (you do have a stock electrical gauge don't you?)  Therefore, if the electrical temperature gauge is working correctly, that says the voltage stabilizer is working.

 

You said the sending unit is new.  You will have to confirm for yourself that you have the correct sending unit.  I know that sometime in the early 1990s the sending unit changed from the early type with a more-or-less straight float arm to one with a "Z" bend in the arm.  The later bent arm sender was used on the cars with fuel injection and those that used the later fuel injection tank.   If the wrong sending unit is installed in a tank the float arm is likely to bind and prevent the gauge reading from changing.  Since the tank is often near empty when sending units are changed... that means the gauge might just read near empty all the time.

 

There are two electrical tests to carry out.  With the ignition on, disconnect the green/black sending unit wire at the tank.  Hold the disconnected green/black wire terminal to the black wire terminal on the sending unit.  Have a friend watch the gas gauge while you do this.  If the gauge goes to full, that suggests a problem with the sending unit.  If the gauge does NOT go to full, that says there could be a wiring problem or problem with the gauge.  

 

For the second test, have the ignition on again and use a jumper wire to connect the terminal on the green/black sending unit wire directly to the battery (-) terminal.  Again, have a friend watch the gauge.  If the fuel gauge goes to full in this test... but not in either of the tests above, that says the black earth wire on the sending unit has a problem.  If the gauge does NOT go to full during this test, that suggests a problem with the gauge itself.

[Wiggywithahailo]

Thank you will carry out test at the weekend and report back

[Wiggywithahailo]

Hi all I have carried out both tests and in both the gauge goes to full?
Any help would be great thank you

[dklawson]

If shorting the green/black fuel sending unit wire to earth makes the fuel gauge go "full scale", that says the voltage stabilizer, gauge, and wiring to the sending unit is OK.  If subsequently shorting the green/black sending unit wire to the black earth wire on the sender makes the fuel gauge go "full scale", that says the earth wire on the sending unit is also OK.

 

What's left?  The sending unit.  I know you said this was new.  However, you also said the car was a '91.  That's about when the tank and sending unit changed.  The later sending units had a "Z" bend in the float arm to work with the later tank.  If you use the wrong sender for the tank you have the float arm can become wedged/stuck so the fuel gauge reading never changes.  Where it gets stuck (full, empty, mid-scale) is something I cannot answer.

 

What to check next?  Drive the car until the level of fuel is below the level of the sending unit hole, then remove the sending unit.  Make sure the float does not have gasoline inside.  A float that is full of gas will make the gauge always read empty.  While the sender is out of the tank, leave the wires connected to it, switch the ignition to "run", and operate the float arm by hand as you watch the gauge.  Let us know if you can make the gauge change its reading by moving the arm all the way "up" to the full position.