13 replies to this topic

[n00b]

Hi all, I have tried to wire in a water temperature gauge in, the TIM electrical one, and am having no joy. And i have tried searching TMF and MiniFinity forums but cant find any solutions!

I have a decent earth as the illumination lamp on the gauge works when i turn my headlamps on, I have run a wire straight from the temperature sender (which was included) to the gauge.

I have isolated the fuse for switched ignition live, which is also wired to the gauge. I did this by taking fuses out, one by one, untill my radio didnt work when i turned the key to ignition. I just cant see why it doesnt work? lol.

Has anybody else had troubles with this, or am i being stupid? I have wired more complex things into the mini before but this has baffled me! I have followed the instructions step by step, but the gauge doesnt move! Might be tempted to swap the cables from the temp sender and ignition live on the gauge and see if that works?

Any suggestions is a great help, im all ears!

Many Thanks ERic

[dklawson]

Are you trying to use the Smiths sending unit with the TIM gauge? If so... don't. Find, buy, or make an adapter to use the TIM sending unit with the TIM gauge. If you are using the TIM sending unit, how and where is it mounted? It must have a good earth connection.

[n00b]

I am using the temp sending unit supplied with the Tim gauge, so its a Tim sedning unit. It is mounted where the original blanking nut was just under the thermostat housing, on the cylinder head. Think that is a good earth, and the engine earth strap is new. Many thanks ERic

[dklawson]

I'm glad to hear that you're using the matching TIM sending unit.

I don't have access to any TIM schematics or wiring diagrams. However, the general practice with aftermarket gauges is to follow a common wiring color code where:
Black = earth
Red = +12V (switched)
White = illumination
Green = Sense (sending unit)

Always refer to the wiring diagram that came with the gauge. However, if you've lost the gauge, try and follow the list above.

[n00b]

Thanks, the instructions are exactly the same! And it still wont budge! With the help of a volt meter i found the voltage that the temp sender produces is the same at different temperatures. Im sure this isnt correct! So i have put the fault down to a dodgy temp sender even though it is brand new! Will be returning it tommorow! Not happy! lol Many thanks for all the help! ERic

[Dan]

The sender does nothing to the voltage at all. The gauge is not powered by the sender, it's powered by the ignition (by the way you should make sure it's on with the key in the ignition position, not the accessory position. The radio should be on the accessory circuit although yours may not be, finding which fuse to use is easy with the workshop manual). The sender varies its resistance between the terminal and earth according to temperature, changing the amount of current drawn through the gauge which is what the gauge indicates. The voltage should be the same all the time. The earth at the gauge isn't earthing the instrument, it's just for the lamp.

[n00b]

Using a voltmeter there is only a voltage from the ignition wire that goes to the gauge when the key is turned to the ignition, and when the engine is running. I really cant understand why it isnt working? I have an ignition live feed which is only on when the key is on the ignition, The illumination lamp works with either sidelights or headlamps on, so there must be a decent earth, and the wire from the sender goes straight into the gauge!

I have gone through the wiring several times and have tested for loose connections and have tried different earth positions but the gauge still doesnt read anything. I am starting to get annoyed with it. I have tried earthing the sender wire that comes from the gauge and the gauge reads maximum. Would have thought faulty gauge but it works when the sender wire is earthed? Any other ideas?

ERic

[cambiker71]

Using a voltmeter there is only a voltage from the ignition wire that goes to the gauge when the key is turned to the ignition, and when the engine is running. I really cant understand why it isnt working? I have an ignition live feed which is only on when the key is on the ignition, The illumination lamp works with either sidelights or headlamps on, so there must be a decent earth, and the wire from the sender goes straight into the gauge!

I have gone through the wiring several times and have tested for loose connections and have tried different earth positions but the gauge still doesnt read anything. I am starting to get annoyed with it. I have tried earthing the sender wire that comes from the gauge and the gauge reads maximum. Would have thought faulty gauge but it works when the sender wire is earthed? Any other ideas?

ERic

Sounds like a faulty sender unit, if the guage reads high when the sender wire connection is earthed and the ignition key is in the 'run' position, then the circuit is working, try taking the unit out connect the wire back on to it and add an earth to the engine (jump lead will work nicely) then heat up the sender and see if the guage moves, a lighter flame held a little way under will do, or pour hot water over it (carefully)

[dklawson]

No additional suggestions from me. As Dan explained, the sending unit doesn't produce electricity and you really can't go by voltage measurements with the sense wire attached or not. The sending unit is a variable resistor that decreases in resistance as the temperature increases. Depending on the construction of the gauge there may or may not be measureable voltage on the sense wire.

The fact that you can make the gauge read high when you short the sense lead to earth indicates that the gauge is probably OK and that the problem is with the sending unit as you said. You can further test the sending unit by putting your multimeter in resistance (ohms) mode. Disconnect the gauge's sense wire and measure the resistance between the sending unit's spade lug and engine earth. You should find several hundred ohms when cold. Start the engine and allow it to reach operating temperature. Repeat your resistance measurement. The value should have decreased by several hundred ohms.

If you see no appreciable change in the sending unit resistance you have confirmed that it's not working and you are justified in taking it back for exchange.

[n00b]

Many thanks! will try it tomorrow, il let you know if it works or not! Thank you for the quick reply! ERic

[Ethel]

Don't know if you have any figures for the temp sensor, but you could test it by measuring the resistance between the sensor's connector and earth as the engine warms up. You could also use a continuity tester to check it isn't the earth to the head in the same way.

[dklawson]

you could test it by measuring the resistance between the sensor's connector and earth as the engine warms up.

That sounds familiar....

[Ethel]

Since I had one to hand I thought a 'how it works' could be in order.

All you'll find inside a gauge is an old analogue gauge is a length of wire wound round a bimetallic strip linked to the needle - current flows through the wire and heats up the strip which expands and moves the needle.

The gauge is wired in series with the sensor which is just a variable resister that alters the current flowing through the winding.

+12v --- GAUGE --- SENSOR --- EARTH

[dklawson]

That pic is a bit fuzzy Ethel. What brand of gauge did you dissect?