Temperature gauge

[biomed32uk]

I added a temp gauge to the car, all wired in correctly.

The gauge is good, not sure what it came out of but it is a Smiths gauge that to me would have been in a Mini, not sure what else they were used in. It the C - N - H style.

Sender is in the head, I was given this with another purchase on ebay,so unsure about it.

When the car is up to temp the gauge sits about 6mm above the C, I would have expected it to be round the N.

Is there a right and a wrong sender for this gauge ?, by reading it would seem a GTR101, but I see some about with red ends and some with black where the lucar tab is, wondering what the difference is with them, I would assume resistance for different gauges.

Don't want to start getting to technical, working out the voltage to the gauge, measuring the resistance of it and the current required through it to move it N, and the work out what sender resistance is required at running temp.

Any one have any advice, as I am slightly confused by choice of senders.

[Trickydicky]

Have you taken a feed from the voltage regulator at the rear of the fuel gauge?

[biomed32uk]

Richard, yes its fed from the regulator on the back of the speedo.

[Ufudu]

Generally senders and gauges have to be matched if you want some sort of absolute temperature reading AFAIK.

[biomed32uk]

Done a bit more digging and a gtr101 temp senosor spec is approx 50 ohms at 90 deg c.

Popped the gauge out the car, only sitting in the drivers glovebox untili sort a panel out for it, put it on a bench power supply set for 10 volts with a 50 ohm resistor and the gauge moves right onto the N, smack in the middle.

My conclusion is the sensor I have is either wrong or dud, new gtr101 ordered and we'll see how that goes.

Now to sort out a half panel in the drivers glovebox to mount the temp gauge and oil gauge, leaving half useable as I find it quite handy.

[biomed32uk]

New sender turned up today, and decided for some science in the kitchen, with the kettle and a cooking thermometer.

Put the sensor and thermometer into the kettle suspended in the water, and slowly heated it up, gauge all powered up, 90 deg and the gauge is on the N mark. So my gauge a sender combination is OK.

Put the new sender in the car, and out of interest run the same setup with the old sender, give or take a fraction its the same, so nothing wrong with that I suspect.

From the calibrations I did with the gauge I would estimate the car is running around 70 deg, I had the thermostat out when I bought the car a few months ago, and decided to get rid of whatever was in the cooling system and flush all the muck out. It wasn't stuck open then, but nor did I test it and it may even be the wrong one which also wouldn't surprise me.

A new 82 deg stat ordered and we will see how that goes, think its running a little cool, the gauge wasn't telling fibs.

[tysonn]

Get one of these,very useful and cheap too
http://www.ebay.co.uk/itm/Digital-Infra ... 3cd2f81505

[bmcecosse]

My conclusion is that your engine is running lower than 90 C !!! Have you checked it with a simple thermometer in the top tank?? Most Minors were fitted with 74 C thermostats - so they will run at ~ 70 C except on hot days........ Your gauge and sender are fine..... fit an 88 degree thermostat if you want the gauge to run at N.

[biomed32uk]

Yes, my conclusion was that to, after faffing around with the sender.

Pulled the thermostat out, which looked to be new(ish) but also looked a bit twisted, marked as 82 deg. Tried it in a pan of water out of curiosity and it seemed to test OK, but did look marginally open with the twist in it.

Anyway, working from home today, and my lunchtime job was to pop the new stat in, refill and test.

Runs up to the N mark, I can feel the stat come fully open with my hand on the top of the rad and it then settles just under N .

Seems to be much better now, and definitely something screwy with that old stat, job done for this one I think now.

[bmcecosse]

Indeed!