(I did a search first, and found a few posts that confirm my initial observations. I'm hoping someone can give me a firmer answer.)
My Mini's temperature gauge does not appear to be working. The needle is way down at the bottom. The wires going from the temperature sensor to the dashboard appears to be good (light blue/green). Connector #3 at the dash is giving a pulsating +12v. My fuel guage is working. Does this mean it's a temperature guage?
This all needs to be done while the engine is cold
Find the temperature sending unit it will be slender and in most cases have a single wire attached, it can be located on the side of the block, water inlet close to the thermostat housing, on the head it self.
If your mini has an electric fan there will be a temperature switch close to the radiator and will usually have two wires attached.
If your car has an oil pressure gauge this will make it easier the oil sending unit will have a metal bulb with a wire on the end if it. This is not the temperature sending unit.
After you Find the wire to the temperature sending unit unplug the wire, roll the key to the on state if the gauge swings to the far right this will show the gauge working in an un-grounded state if the gauge does nothing, next take a test probe with a low current lamp in it, make sure it is a low current, some of the low current types use a .05ma LED in them
Using the test probe make a connection between the temp lead wire and the block lock at the gauge it should swing to about half
If all the above happened as described above use have a problem with the sending unit, clean the connection if this does not resolve the issue replace the temperature sending unit.
If the sending unit is located any where an air pocket can be created do not remove the radiator cap, this will cause a hot spot in the engine, this will result in you having to pressure bleed the cooling system forcing any trapped air out of the cooling system.
I have an unknown vintage Mini. From all indications, it appears to be mid-80's, with a 1275 engine. It has a mechanical fan.
I've found the sending unit, and attached to it is a LightBlue/Green wire, which goes all the way back to the dashboard's wiring harness.
When I unplug the wire and KOEO, the temperature gauage does NOT move (needle down). (My gauge goes up and down, not left and right.) I've checked that the sending unit is putting up some resistance, but I can't remember how much.
So, you are saying if I short the temp wire to the block, with a low current test light acting as a resistor, my gauge should move half-way, correct?
Yes the sending unit does act like a resistor it is actually a thermistor a temperature sensitive resistor.
You can take a ohm reading when the engine is cold it will read some value, start the engine and let it run a bit, take a new reading and you will see a change.
The value should decrease or increase depending on how the sending unit is matched to the gauge
The send unit is like a voltage divider with a temperature sensitive resistor to ground being the brass case of the sending unit
guage ------------v GND being the engine block
This should give you a real rough idea of the internal workings though there are no working parts with temperature the the material becomes less conductive or more conductive
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