28 replies to this topic

[mister bridger]

1964 mk1. When i turn ignition on fuel guage goes straight up to max despite tank being nearly empty. Cleaned connections on sender and no improvement. Test bulb across terminals doesn't light up but if I bridge the terminals it goes back down. All connections on guage ok - the 3 green cables at bottom of pic. Any ideas?

[Phaeton]

The fuel gauge works by putting a voltage through the gauge & then via the sender to earth. When the tank is full there is very little resistance in the coil on the sender which gives a full reading, as the fuel goes down the resistance gets greater & the fuel gauge shows a lower amount.

What happens if you unplug the sender unit & switch the ignition on? If the gauge goes down then the sender is faulty.
If the gauge stays on full then it looks like you have an earth fault on the wire from the gauge to the sender.
The only other thing to check is the voltage going into the gauge it should be 10V not 12V you should have a voltage stabilise in the circuit.

Alan...

[mister bridger]

The fuel gauge works by putting a voltage through the gauge & then via the sender to earth. When the tank is full there is very little resistance in the coil on the sender which gives a full reading, as the fuel goes down the resistance gets greater & the fuel gauge shows a lower amount.

What happens if you unplug the sender unit & switch the ignition on? If the gauge goes down then the sender is faulty.
If the gauge stays on full then it looks like you have an earth fault on the wire from the gauge to the sender.
The only other thing to check is the voltage going into the gauge it should be 10V not 12V you should have a voltage stabilise in the circuit.

Alan...

Undid one connection on sender and guage stayed up, likewise when i connected the earth terminal to a known good earth

[Phaeton]

If you pull the wire off the back of the gauge (the one that goes to the sender) does the gauge drop? If you put it back on & pull it off the sender & it stays up there is an earth fault is in the wire between them To positively identify it, if you have a long enough piece of wire run a temporary one putside the car between the gauge & sender to see if thet resolves it.

Alan...

[mister bridger]

If you pull the wire off the back of the gauge (the one that goes to the sender) does the gauge drop? If you put it back on & pull it off the sender & it stays up there is an earth fault is in the wire between them To positively identify it, if you have a long enough piece of wire run a temporary one putside the car between the gauge & sender to see if thet resolves it.

Alan...

It's dark, it's snowing and I'm kn***ered so I'll try that tomorrow! Thanks for your help that sounds like it should identify the problem.

[dklawson]

1964 was a transition year for the Mini's gauge system and while I greatly appreciate your posting the picture.

Let me ask you several questions.
1) Does the sending unit bolt onto the tank with six screws OR is it held in place with the bayonet ring?
2) Does your fuel gauge needle "JUMP" up to full when you turn on the ignition or does it slowly "creep" up to full?

In September 1964 the voltage stabilizer was added to the Mini. The complete gauge and sender packaged changed at that time. You cannot use an early sender with a later gauge and vise versa. The sender's resistance ranges go in opposite directions and cover a different resistance range.

Later fuel gauges have two little holes (or cork disks) on their back side in addition to the lugs for the wires. They only work with senders that mount with the bayonet ring. The later gauges have needles that move SLOWLY.

Early fuel gauges respond instantly when you turn the key on. On their backs they have two little nuts in addition to the lugs for the wires. They only work with the sending units that bolt onto the tank. The early gauges MUST (repeat: must, must, must) have a good earth connection. If the gauge looses its earth connection it will read full all the time. On the early gauges if the wire to/from the sending unit fails or is removed from the tank... the gauge will read full. If the sending unit's internal resistance wire fails... it CAN make the gauge read full depending on where the break occurs. If you short the sending unit wire to ground the gauge will read empty. This is EXACTLY opposite to what the late gauge system does under these conditions.

So, post back with which sender and gauge type you have and be sure to confirm that the gauge itself has a good (really good) earth connection. (Remove the gauge mounting screws, clean them, sand the eyelets on the gauge that they pass through... then reinsert the screws... perhaps with a dedicated earth wire attached).

[stormintrooper]

In September 1964 the voltage stabilizer was added to the Mini.

Where would this be located on my '89 austin mayfair?

[mister bridger]

1964 was a transition year for the Mini's gauge system and while I greatly appreciate your posting the picture.

Let me ask you several questions.
1) Does the sending unit bolt onto the tank with six screws OR is it held in place with the bayonet ring?
2) Does your fuel gauge needle "JUMP" up to full when you turn on the ignition or does it slowly "creep" up to full?

In September 1964 the voltage stabilizer was added to the Mini. The complete gauge and sender packaged changed at that time. You cannot use an early sender with a later gauge and vise versa. The sender's resistance ranges go in opposite directions and cover a different resistance range.

Later fuel gauges have two little holes (or cork disks) on their back side in addition to the lugs for the wires. They only work with senders that mount with the bayonet ring. The later gauges have needles that move SLOWLY.

Early fuel gauges respond instantly when you turn the key on. On their backs they have two little nuts in addition to the lugs for the wires. They only work with the sending units that bolt onto the tank. The early gauges MUST (repeat: must, must, must) have a good earth connection. If the gauge looses its earth connection it will read full all the time. On the early gauges if the wire to/from the sending unit fails or is removed from the tank... the gauge will read full. If the sending unit's internal resistance wire fails... it CAN make the gauge read full depending on where the break occurs. If you short the sending unit wire to ground the gauge will read empty. This is EXACTLY opposite to what the late gauge system does under these conditions.

So, post back with which sender and gauge type you have and be sure to confirm that the gauge itself has a good (really good) earth connection. (Remove the gauge mounting screws, clean them, sand the eyelets on the gauge that they pass through... then reinsert the screws... perhaps with a dedicated earth wire attached).

As before it's dark snowing etc so will check all the details in the morning. My various manuals give wiring diagrams for up to 64 and 64 onwards so they're not very useful! Gauge jumps immediately to full. Car registered 21/07/64 so presumably no voltage reg. Gauge was working fine before - nothing's been changed.

[dklawson]

Stormintrooper, an '89 would be much too late for me to give you an accurate answer on. All I can say is that on the later cars with Smiths gauges, the stabilizer is attached to the back of the plastic gauge cluster housing. On the still later Nippon-Seiki gauges I understand the stabilizer is buried inside but I have no first-hand experience with either gauge cluster.

Mister bridger, no worries. Just passing information along. The gauge transition was "around" September of '64. Based on both your description of gauge performance and the build date, you've got a pre-stabilizer system. Since the problem suddenly developed, look for damage to the earth connection at the sender, and on the gauge itself. The quick test for your situation would be to switch on the ignition and pull the green/black wire off the sending unit and short it to earth. With the early gauges this should make the gauge read EMPTY. Make sure you choose a good earthing point for the wire or run a jumper over to the battery's earth cable. If the gauge still reads full, look at those gauge mounting screws that I mentioned earlier. All you need is a bit of corrosion under the heads of the screws and you'll loose the gauge earth.

[stormintrooper]

well due to me giving them a clean i have fully dismantled my clock cluster and have found no such thing to indicate a voltage stabiliser

[dklawson]

On an '89 the stabilizer will be there somewhere. If the gauges are Nippon-Seiki the stabilizer will be "inside" and is likely to be an electronic "chip" shaped like a large transistor (TO-92 housing). If the gauges are Smiths, it should be on the back somewhere. See the JPGs below.

Look for item 13. It should be plugged into the back side of the cluster.
http://www.heritageg...inicat10-29.gif

The stabilizer will look like this (without the flat metal strip with the hole in it).
http://www.holden.co...ges/070_118.jpg

[mister bridger]

Mister bridger, no worries. Just passing information along. The gauge transition was "around" September of '64. Based on both your description of gauge performance and the build date, you've got a pre-stabilizer system. Since the problem suddenly developed, look for damage to the earth connection at the sender, and on the gauge itself. The quick test for your situation would be to switch on the ignition and pull the green/black wire off the sending unit and short it to earth. With the early gauges this should make the gauge read EMPTY. Make sure you choose a good earthing point for the wire or run a jumper over to the battery's earth cable. If the gauge still reads full, look at those gauge mounting screws that I mentioned earlier. All you need is a bit of corrosion under the heads of the screws and you'll loose the gauge earth.

I've broken it! tied to undo the small right hand nut on back of gauge and it broke something inside and now just spins. Then realised you probably meant the small slotted screws mounting gauge to speedo. AAAARGH! by the way sender is definitely bayonet type (to my surprise). Haven't had this car on the road yet and it's only ever had a small amount of petrol in it - could it be they were always mismatched? Plenty of other bodges been done on it in the past. Doesnt explain how used to read nearly empty and then went to full though. Have checked earths carefully and they all seemed good. So what replacement gauge do I now need to find I am totally confused!

[stormintrooper]

On an '89 the stabilizer will be there somewhere. If the gauges are Nippon-Seiki the stabilizer will be "inside" and is likely to be an electronic "chip" shaped like a large transistor (TO-92 housing). If the gauges are Smiths, it should be on the back somewhere. See the JPGs below.

Look for item 13. It should be plugged into the back side of the cluster.
http://www.heritageg...inicat10-29.gif

The stabilizer will look like this (without the flat metal strip with the hole in it).
http://www.holden.co...ges/070_118.jpg

as i said i fully dismantled my clocks...i am not sure as to which kind they are but there isnt a chip nor is there that item 13 you showed me

and my gauges have worked fine except for the temp which i found to be a dodgy temp sender

Edited by stormintrooper, 13 February 2009 - 11:16 AM.

[mister bridger]

Mister bridger, no worries. Just passing information along. The gauge transition was "around" September of '64. Based on both your description of gauge performance and the build date, you've got a pre-stabilizer system. Since the problem suddenly developed, look for damage to the earth connection at the sender, and on the gauge itself. The quick test for your situation would be to switch on the ignition and pull the green/black wire off the sending unit and short it to earth. With the early gauges this should make the gauge read EMPTY. Make sure you choose a good earthing point for the wire or run a jumper over to the battery's earth cable. If the gauge still reads full, look at those gauge mounting screws that I mentioned earlier. All you need is a bit of corrosion under the heads of the screws and you'll loose the gauge earth.

I've broken it! tied to undo the small right hand nut on back of gauge and it broke something inside and now just spins. Then realised you probably meant the small slotted screws mounting gauge to speedo. AAAARGH! by the way sender is definitely bayonet type (to my surprise). Haven't had this car on the road yet and it's only ever had a small amount of petrol in it - could it be they were always mismatched? Plenty of other bodges been done on it in the past. Doesnt explain how used to read nearly empty and then went to full though. Have checked earths carefully and they all seemed good. So what replacement gauge do I now need to find I am totally confused!

bump

[midridge2]

from the pictures you have the newer sender unit and the newer speedo housing, there is no sign of the voltage stabiliser unit there, it should be at the top.
in my opinion if it was working fine before, then its the main + cable is earthing out or the sender unit is stuck in the full position.