Voltage Stabiliser

[mike.perry]

I have just fitted an electric temp gauge (magnolia to match the speedo) to my Series MM, which required a voltage stabiliser. I was going to use a spare one from a 1098 speedo. However I was informed that the V/S is polarity conscious and as my MM is neg earth the 1098 V/ S would not work as it would be pos earth. This would theoretically affect the fuel gauges of cars converted to neg earth.
Any comments?

[bmcecosse]

Not at all - it's a bi-metallic strip and has no care what polarity it sees!

[Dean]

are you sure BMC? You can buy both positive and negative voltage stabilisers.

[bmcecosse]

Aye - if you buy a modern electronic one - but the original Minor unit cares not a jot!

[IslipMinor]

The original one worked very well with negative earth for my oil temperature gauge. It has since been replaced by a solid state one from Maplins. Before fitting the gauge I would suggest that you check the reading in a pan of boiling water first. I was getting concerned over the last 3/4 years about increasing oil temperature, and initially put down to changes in spec of the engine, higher CR etc. The water temperature never varied (mechanical capillary gauge), so just this year checked the oil gauge and it was more than 20°C over-reading at 100°C!! Since re-calibrated the gauge by taking it apart very gently, and the oil runs nicely around 90/110°C again.

[mike.perry]

How do I check the sensor in a pan of boiling water when it needs to be earthed? I can check a capillary gauge ok.
What is the best method to check that the V/S is working?

[bmcecosse]

That's very hot oil Richard - I always used a good big oil cooler with my competition engines.

[mike.perry]

I decided to use the spare fuel gauge V/S but the needle is only just off the stop, 55deg when the engine is hot. I will dip the rad with the capillary gauge tomorrow and compare

[IslipMinor]

Hi Roy,

When I thought I had increasing oil temperature, I rang the technical department of Castrol as the oil is Castrol Edge Sport 10w/60 full synthetic, and they said that the ideal temperature was around 100/110°C, with a max of around 130°C, which is what I was seeing on the gauge, and sometimes a bit more! The oil pressure was always good, even at the gauge reading of "130°C+", 30+ on idle and 60/70 at 3,000 rpm +.

I am using the MG Metro water cooled oil cooler, and was planning to fit a conventional air to oil cooler either instead or as well as, but with air temperatures up to 40°C in Italy, lots of mountain passes and 4 track sessions on the Euroclassic this summer down to Rome and back, the oil temperature behaved perfectly.

[bmcecosse]

Well - I guess the Castrol lads will know! I could never keep decent oil pressure without a cooler - but they were (in later years when I had decent power) Mini engines and of course they also have the gears mangling the oil in the sump.

[mike.perry]

I stuck a capillery sensor in the top of the rad and the gauge read about 70 deg
I wired the electric gauge direct and it climbed to about 90 deg, so the gauge works
I measured the voltage between the output (10V) terminal and earth and the meter jumped around at about 3 volts.
Next test is with the v/s from the Traveller

[bmcecosse]

It is an 'on/off' action from the bimetal strip - can't really measure the voltage like that with a meter. the on/off is supposed to be equivalent heating effect to 10 volts - but you won't be able to measure 10 volts.

[Declan_Burns]

Mike,
Repeat your test. 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.
Here's a 50 ohm pot (N36BR for £0.49) which will also work:
http://www.maplin.co.uk/sub-miniature-f ... eters-6499

Regards
Declan

[mike.perry]

Thanks for the info but it is slightly over my head. Is there another name for a potentiometer? What do I ask for in my local Maplins without disclosing my total lack of knowledge of electronics?
The Mini Workshop Manual Issue 1, 4908, Sect. N7 (later editions do not include this info), states
"Check mean voltage between output terminal I and earth, which should be 10V"[frame][/frame]

[Declan_Burns]

Mike,
It's all very simple-just ask for a 50ohm preset or give them their part no. -see above.
It has two terminals and a wiper. Connect the wiper to one of the two terminals-it doesnt matter which one and connect the two terminals between the gauge and sender and adjust the wiper-that's basically it. Only takes a few minutes.
http://www.kpsec.freeuk.com/components/vres.htm
Regards
Declan

[bmcecosse]

I would love to know how they measure that 10 volts. Probably why it's not in the later versions.......

[mike.perry]

Would a slow moving dial type voltmeter read it as opposed to an instant reading digital instrument?

[bmcecosse]

I think it will still flick up and down........

[Alec]

Hello Mike,

a well damped analogue meter would give a very near reading I would think. I don't know the frequency of the regulator but would think it is fast enough for the meter not to try and follow the waveform.

Alec

[mike.perry]

I seem to have sorted the problem. I used a spare v/s off the back of a speedo clamped to the back of the gauge mounting plate to earth it. The gauge is now reading about 75 deg which agrees with a capillary gauge dipped in the radiator. I know that the temp. is a bit low but that is probably due to the stat needing changing which I am reluctant to do as the housing is a pig to remove and reseal.