10 replies to this topic

[ODD1991]

Model: Ritz
Year:1985
Description of problem (please be as in depth as possible):
hi, i wired my smiths water temp gauge up earlier it it was acting strange.

it was reading the temp at about 40 degrees c but it would twitch back to 0 about every 3 seconds or so.

is the gauge broke is it normal forit to do that when the engine is cold?

thanks


Any non-standard parts that might be involved with the problem?

[dklawson]

What is the fuel gauge doing?

It is not normal for the gauge to twitch. I suspect the problem is not in the gauge itself but in the voltage stabilizer that powers it.

You said you rewired the gauge. What did you do during this process? How did you rewire the gauge?

[bmcecosse]

The stabiliser is designed to work with a 'hot wire' gauge - it attempts to 'regulate' the voltage to the gauge by clicking on and off - to give an average of ~10 volts. Seems like your gauge is not 'hot wire' - and so each time the regulator clicks off - so does your gauge! You could connect it directly to 12 volt supply (ie not through the reg) - but it may then read high - try it!

Edited by bmcecosse, 25 January 2010 - 10:02 PM.

[ODD1991]

The stabiliser is designed to work with a 'hot wire' gauge - it attempts to 'regulate' the voltage to the gauge by clicking on and off - to give an average of ~10 volts. Seems like your gauge is not 'hot wire' - and so each time the regulator clicks off - so does your gauge! You could connect it directly to 12 volt supply (ie not through the reg) - but it may then read high - try it!

hi thanks for the reply, i does seem like it turns on and off on its own. i iwll try and connect it to the live feed. i will let you know what happens.

how do i find out if a gauge is a 'hot wire gauge'?

by the way what i mean by rewire is connecting the gauge the the temp sender wire and the wire from the stabiliser as stated in my haynes manual.

thanks again

[dklawson]

To elaborate on what Roy stated, when he talks about the gauge being a "hot wire" device, he means it works by internal resistance heating of a bimetallic strip hooked to the gauge pointer. It's what your Mini has if it was built after September 1964. Those gauges use a voltage stabilizer to provide a controlled 10V to the gauges. Bypassing the stabilizer will supply the gauge with full system voltage. That's typically over 14V when the engine is running. That's 40% more voltage than the gauge was designed to operate on and that WILL (not might) make the gauge read high. It will also shorten the life of the gauge.

I asked what the fuel gauge was doing because both the fuel gauge and the temperature gauge are supplied 10V by the voltage stabilizer. However, the stabilizer is not a modern bit of electronics, it is an electromechanical switching device. It opens and closes contact points to provide an "average" of 10V to the gauge. The important bit to keep in mind here is that part about points opening and closing. The stabilizer points can open and close anywhere from several times per second to once every few seconds. Each stabilizer is different. If both the fuel and temp gauge are twitching, you could be watching the stabilizer contacts opening and closing VERY slowly.

If you see twitching in both your fuel gauge and the temperature gauge, it would indicate a faulty voltage stabilizer. If your fuel gauge is behaving normally, the twitching you see in the temp gauge may indeed be a failure of the temp gauge itself... or (less likely) the sending unit. If the fuel gauge is behaving normally, the next time the fuel gauge starts twitching open the bonnet and disconnect the temp sending unit wire and earth it. The gauge should go to "hot". If it doesn't, the problem is in the gauge. If it goes to hot and continues to twitch, the problem is in the gauge.

EDIT:

by the way what i mean by rewire is connecting the gauge the the temp sender wire and the wire from the stabiliser as stated in my haynes manual.

When you rewired these components there are a couple of things to keep in mind and to go back and check. The stabilizer MUST have a good earth connection. It's case provides that earth and without it the stabilizer will not function properly. Second, check your connections to/from the stabilizer. The switched supply from the fuse box will originally be on a dark green wire coming from the fuse box. That wire MUST go to the stabilizer terminal marked with "B" (for battery). The gauges will connect to the stabilizer terminal marked with "I". These marking letters will be on the little PC Board next to the stabilizer terminals. If you hook the wires up backwards, you effectively have no stabilizer and are passing full system voltage. (see paragraph 1 above).

[ODD1991]

To elaborate on what Roy stated, when he talks about the gauge being a "hot wire" device, he means it works by internal resistance heating of a bimetallic strip hooked to the gauge pointer. It's what your Mini has if it was built after September 1964. Those gauges use a voltage stabilizer to provide a controlled 10V to the gauges. Bypassing the stabilizer will supply the gauge with full system voltage. That's typically over 14V when the engine is running. That's 40% more voltage than the gauge was designed to operate on and that WILL (not might) make the gauge read high. It will also shorten the life of the gauge.

I asked what the fuel gauge was doing because both the fuel gauge and the temperature gauge are supplied 10V by the voltage stabilizer. However, the stabilizer is not a modern bit of electronics, it is an electromechanical switching device. It opens and closes contact points to provide an "average" of 10V to the gauge. The important bit to keep in mind here is that part about points opening and closing. The stabilizer points can open and close anywhere from several times per second to once every few seconds. Each stabilizer is different. If both the fuel and temp gauge are twitching, you could be watching the stabilizer contacts opening and closing VERY slowly.

If you see twitching in both your fuel gauge and the temperature gauge, it would indicate a faulty voltage stabilizer. If your fuel gauge is behaving normally, the twitching you see in the temp gauge may indeed be a failure of the temp gauge itself... or (less likely) the sending unit. If the fuel gauge is behaving normally, the next time the fuel gauge starts twitching open the bonnet and disconnect the temp sending unit wire and earth it. The gauge should go to "hot". If it doesn't, the problem is in the gauge. If it goes to hot and continues to twitch, the problem is in the gauge.

EDIT:

by the way what i mean by rewire is connecting the gauge the the temp sender wire and the wire from the stabiliser as stated in my haynes manual.

When you rewired these components there are a couple of things to keep in mind and to go back and check. The stabilizer MUST have a good earth connection. It's case provides that earth and without it the stabilizer will not function properly. Second, check your connections to/from the stabilizer. The switched supply from the fuse box will originally be on a dark green wire coming from the fuse box. That wire MUST go to the stabilizer terminal marked with "B" (for battery). The gauges will connect to the stabilizer terminal marked with "I". These marking letters will be on the little PC Board next to the stabilizer terminals. If you hook the wires up backwards, you effectively have no stabilizer and are passing full system voltage. (see paragraph 1 above).

hi thanks that info is a great help. the fuel gauge works fine with no twitching.

i have the ignition feed going to the stabiliser to the battery connection do i need another wire going to the stabiliser for it to work fine?

the fuel gauge works fine with just a feed from the ignition. by the way i dont think the temp gauge is the original one out of a mini. its a quadrant gauge with specific temperatures instead of just cold hot and normal. would this make a difference?

thanks again the help is much appreciated.

[bmcecosse]

Sounds like wrong gauge - and reading low tells me it's not getting enough volts. Hence - try it directly on the 12 volts (yes=14 when charging!) and see if it reads correctly. Obviously - if it goes off the scale at the hot end - don't leave it connected!

[dklawson]

BOTH fuel and electric temperature gauges (Smiths brand) must be connected to the voltage stabilizer's "I" terminal.

If you have wired your fuel gauge directly to the ignition switch, that is wrong. Just like I mentioned in my last post about your temperature gauge, supplying the gauge directly without the stabilizer supplies up to 40% too much voltage resulting in "high" gauge readings and reduced gauge life. The correct wiring situation would be a dark green, switched power supply from the fuse box going to the stabilizer's "B" (battery) terminal. The two gauges will each have a wire (usually light green) going to the stabilizer's "I" (instrument) terminal. Again, both gauges are powered by the stabilizer if they are Smiths gauges. If that's not what you have, make the proper connections to both gauges and then see what's happening.

When Roy mentions your possibly not having the right gauge, there are several possibilities. First you could have a later model gauge from some other car which is not compatible with the Mini sending unit. The gauge would work but not necessarily give the correct readings. However, it probably wouldn't "twitch" just because it's the wrong gauge. Another possibility is that you have fitted an early style gauge (pre-1965). Those gauges are totally different, don't use the stabilizer, and are incompatible with the sending units for later gauges. The early gauges are identified by a different needle shape. The early gauges have needles that are "skinnier" with a more-or-less square cut end. Later gauges have wider needles that terminate in a "pointy" end. The needles on early gauges will bounce around when you hit bumps while driving. Later gauges will only vibrate a tiny bit under the same circumstances. Out of the dashboard, the needle of an early gauge will flop around when you move the gauge about while a later gauge's needle will barely move and will just vibrate a bit.

If you're unsure about your gauges, feel free to post pictures and I'm sure one of us will be able to identify them.

[ODD1991]

BOTH fuel and electric temperature gauges (Smiths brand) must be connected to the voltage stabilizer's "I" terminal.

If you have wired your fuel gauge directly to the ignition switch, that is wrong. Just like I mentioned in my last post about your temperature gauge, supplying the gauge directly without the stabilizer supplies up to 40% too much voltage resulting in "high" gauge readings and reduced gauge life. The correct wiring situation would be a dark green, switched power supply from the fuse box going to the stabilizer's "B" (battery) terminal. The two gauges will each have a wire (usually light green) going to the stabilizer's "I" (instrument) terminal. Again, both gauges are powered by the stabilizer if they are Smiths gauges. If that's not what you have, make the proper connections to both gauges and then see what's happening.

When Roy mentions your possibly not having the right gauge, there are several possibilities. First you could have a later model gauge from some other car which is not compatible with the Mini sending unit. The gauge would work but not necessarily give the correct readings. However, it probably wouldn't "twitch" just because it's the wrong gauge. Another possibility is that you have fitted an early style gauge (pre-1965). Those gauges are totally different, don't use the stabilizer, and are incompatible with the sending units for later gauges. The early gauges are identified by a different needle shape. The early gauges have needles that are "skinnier" with a more-or-less square cut end. Later gauges have wider needles that terminate in a "pointy" end. The needles on early gauges will bounce around when you hit bumps while driving. Later gauges will only vibrate a tiny bit under the same circumstances. Out of the dashboard, the needle of an early gauge will flop around when you move the gauge about while a later gauge's needle will barely move and will just vibrate a bit.

If you're unsure about your gauges, feel free to post pictures and I'm sure one of us will be able to identify them.

i have wired the fuel and the temp gauge to the "i" connection on the stabilizer but only got one wire going into the b connections and that is the wire from ignition. that wire is white.

should i have another wire going to the stabilizer?

thanks again

[Ethel]

No.

Have you checked all the connections to the sender? You could try swapping the sensor wires between the gauges and see if the fault swaps with them.

[dklawson]

White wires are usually unfused and switched. Unfused will work but has obvious safety implications.

As a footnote, sometimes, on some cars, there is a second wire on the "B" terminal. However, that wire often is not part of the gauge circuit. Because it's a switched, fused wire on "B", the "B" terminal is sometimes used as a junction/connection for wires going to other circuits. For example, I believe on my Mk1 the ventilation blower is connected to the "B" terminal.