Morris Minor Owners Club

I've eventualy got my temperature gauge to work properly - it was shorted out inside the gauge. It still gave full scale deflection when shorting the temp sender lead to earth. So I had already mistakenly changed the sensor which wasnt faulty.
The only difference between the new sensor and the old one is the colour of the centrepiece the new one is red the old one black.

The new one over reads by about 10 degrees C the old one is perfect

Does anyone have any information about these sensors. I got the clue from Jonathon who, in an other post, mentioned there were quite a few different ones for Smiths gauges

Sorry - don't know anything about sensor colour coding. How do you KNOW which one is correct ?

Stuffed the thermocouple from a digital temperature gauge (calibrated in a pan of boiling water) down the the top hose. At 90C on the digital gauge the 'black' stat gives a fraction over 90 the 'red' stat gives about 105.

No difference in the senders whatsoever except the colour. I also assume that there is another type of sender for the warning light go/no go which presumably also looks the same. Could be one of the reasons so many people moan about their temperature gauge not working or being inacurate

Warning light ?

????????????? There is no temperature warning light on a Minor
Ignition, Oil pressure
Main beam, OiI filter

Then why do the likes of Bull Motif sell:-

Part No 10M229 temp sender for warning light and
Part No 10M229A temp sender for gauge

I didnt suggest that the warning light was in the speedo presumably it is just as easy to retro fit a warning light as it is a gauge (easier some would say) therefore it follows that some people must have a warning light 'cos if they didnt then why would a reputable parts supplier sell them!

In any case my point was the senders look identical but are obviously internally different!

Bill,
When I changed the gauge from the mini C-N-H type to the 90 ... 140°C type it overread. The sensor was the red one manufactured by Intermotor part no 5271. Not just the sensors are different but also the gauges. Fitting a 22 ohm 0.1 Watt trim potentiometer in series with the wire from the sensor cures this. Very easy to do and you can adjust the gauge to match the measured temperature perfectly. The potentiometer is then insulated and hidden under the dash.
I measured the resistance on the red one at 20°C this morning and it read 0.81k ohms. I have a black one which came with my 940 head and it read 2.25k ohms.
If it underreads, the potentiometer has to be connected in parallel with the sensor. The potentiometer is available from any electronics shop for a few pence.
Regards
Declan

I have a temperature sensor on the front of the head (below the thermostat housing) with a green wire that disappears in to the loom. I don't have a temperature gauge so presume there's a light somewhere. At least - I thought it was a temperature sensor.

Presumably you could simply connect the temperature light sender to the completely useless oil filter light and hence you would have some form of indication of overheating other than clouds of steam from under the bonnet.

Mine also has a green wire connected to the sender which disappears into the loom so its not an afterthought its original. Its not for the above mentioned filter light. In mine it feeds the temperature gauge (not original).

Minors never came fitted with temp gauges or 'overheat' warning lights! That green wire must be for something else - it should not be connected to the cylinder head.

I fully appreciate the fact that Minors were not fitted with either a warning light or a temp gauge but the green wire which sgray alludes to is also fitted to mine. Its part of the loom and on mine it has been used to connect the sender to the temp gauge. and in sgray's case is connected to heaven knows what. There is nothing around that area that is not connected (OK I dispensed with the filter light) so,purely for academic interest, what was it for?

The filter blocked warning light I think! However - should be green/yellow wire. Green is the colour used for all fused ignition switched wires - and there shouldn't be any in the engine compartment.

I once had a 1961 Pontiac that had "cold" and "hot" idiot lights in it, no gauge. It used to bug me when starting the car on a cold, dark morning in the middle of winter, at about 30 or 40 below, the little green "Cold" light would come on. Sitting there on a cold seat I didn't need a little green light telling me that it was cold, I darned well knew it without prompting.

bmcecosse wrote:The filter blocked warning light I think! However - should be green/yellow wire. Green is the colour used for all fused ignition switched wires - and there shouldn't be any in the engine compartment.

No its not the green/yellow for the filter (I cut that one off) its definately green only and the loom still has the original braiding.

Two green wires I can think of in engine bay area are to brake light switch and flasher relay both from the ign fed fuse....

Well it's very green, perhaps with red (will give it a good clean and check) - it has a spade connector on the end and was fitted to the temperature sensor on the front of the head.
I've no idea if it's original - it just doesn't look like a later edition.

I could try and trace it back to find out where it comes out of the loom, but it's friday and there's beer in the fridge...

It isn't connected anywhere now, because I haven't transferred the sensor from the old head. Perhaps the last Minors had this extra wire fitted for something - mine's a 1970..??

Yes - ok ok - but not on the engine!