PROBLEMS WITH TEMP GUAGES

[geoff12]

Can anyone with more knowledge than me give some advice with regard to wiring up an electric temp guage, I have fitted a new sender to the head with a wire coming off and going to one side of the guage, and a wire from the other spade on the guage going to the spare spade connection on the voltage stabiliser, the other half of this goes to the fuel guage. engine running and warming up with absolutely no flicker or movement of guage, I have tried another smiths guage and getting exactly the same result, with ignition on I am getting power from the wire out of stabiliser, all other electrics are working, am I missing something or are both guages caput.

[katy]

Have you tried switching the 2 wires on the gauge?
Are both the sending unit and the gauge new?
Is the gauge a 12 volt unit?
Do you have a multi-meter to use for testing purposes? (if required)
I believe the voltage stabilizer only puts out about 10 volts, so you should move the feed wire for the temp gauge to the input side of the VS, so you get a proper 12 volts for the gauge.

[geoff12]

Thanks Katy for your reply, the answers to your questions are
1. Yes I have switched both wires on back of guage and blew a fuse on fuse box, changed wires back and replaced fuse so I think wires were correct fist time.
2. Sender screwed into head very new from morris supplier, Guages second hand.
3. Yes both guages 12v.
4. No I havent got a muti meter, and I wouldnt know how to use one.
5. Live connection to guage is connected to green wire that connects to fuel guage.
I am very baffled, I am very suprised that both guages I have tried seem to be dead.

[billlobban]

I am very baffled, I am very suprised that both guages I have tried seem to be dead.

Make that 3. I have exactly the same problem. Replaced the sender unit in the head - no change. Replaced the faulty voltage stabiliser (which made my fuel guage read correctly) - no change. Checked the wiring - no change. I've got a multi meter and I know how to use one but I am no further forward than you are. I am not keen on buying a new guage but cant find any details as to the test criteria for the gauge itself so I guess thats the only solution

[geoff12]

Can end up quite expensive, Ive already bought two and they were supposed to have been in perfect working order!

[bmcecosse]

GAUGE!

Why did it blow a fuse ??? Try simple wire from battery +ve to one terminal - and from the other terminal, a wire to earth. The gauge should go full reading.

[geoff12]

Have no idea why fuse blew, perhaps it was coincidence, Yes I have tried what you suggest, i connected wire to both terminals on guage then one to pos and other to neg on battery, get full reading on guage either way, BAFFLED!

[bmcecosse]

So - if the gauges move with that test - they ARE working! It should be fed with the regulated supply from the voltage unit - so ~10 volts - not the full 12. So - next try - connect from volt reg unit to gauge -and from gauge to earth - does it move ok ? IF not - suspect voltage reg - if yes, but still doesn't work through temp sensor - then obviously the sensor is not right - or is not earthing. Where is it screwed in ??

[simmitc]

Did you use any sealant or PTFE tape when fitting the sender? If so: DON'T. The sender should be a taper fit thread and requires only to be tight to make a seal. It also requires a good connection to the block to complete the earth, and any form of sealant can isolate the sender from the block, thus breaking the circuit.

[geoff12]

Hi Bmecosse, Have disconnected temp sensor wire from back of guage, connected wire from earth to guage and needle has gone from C to H straight away, what is wrong then? I fitted a new temp sensor bought from ESM last week, fitted without sealer or fibre washer to cylinder head beneath thermostat housing, I have even fitted a seperate earth from manifold stud in head to earth incase I wasnt getting a good earth because of cylinder head gasket.

[PSL184]

Leave the gauge wired as you first did it and with ign on take the wire off the sender unit and earth it. If the gauge goes FSD then the problem is either with the sender or the sender is not earthed.

[mike.perry]

If anyone has a Mini workshop manual, there is a suitable wiring diagram on page N8.
The Green/blue wire connects from the gauge to the sensor and the light green wire connects to the I terminal on the voltage stabilizer[frame][/frame] However I still can't get the temp gauge in my Series MM to work

[bmcecosse]

Must be faulty sensor from ESM. Your gauge is working fine if it goes full scale when earthed. Unless of course - the engine isn't getting hot ?????????

[geoff12]

Many thanks for all your help I will get another sensor and let you know how I get on.

[geoff12]

QUESTION FOR BMCECOSSE, Im Confused! If when i disconnected wire from sensor and connected wire to direct earth the guage showed hot surely when wire is connected to a workable sensor (if the newone i have previously bought doesnt work) and another workable one is fitted and i connect the earth wire to it, wont the guage show immediate hot as soon as i turn ignition on as was done when earth wire was connected direct to earth

[bmcecosse]

The sensor is a resistor - variable with temperature. Yours must be 'open circuit' - so no current can flow. When you short direct to earth - you make 0 resistance - so full scale = HOT. A working sensor will give an indication in between - depending on engine temperature.

[geoff12]

Thank you for all your help,Sorry im such a dinosaur, will let you know how i get on,Cheers Geoff

[billlobban]

I mentioned at the top of this post that I had a multimeter and I know how to use it. Well----- all the equipment and knowledge dosnt prevent the occasional senior moment. When I first tried to fix my temperature gauge I (correctly) diagnosed the fault as the temperature sensor. Bought a new one but when I fitted it it leaked and not wanting to strip the threads on my new sensor (you've already guessed) I slobbered it in thread seal - leak cured - gauge still US. Tried and tested everything and coundnt find the fault so gave up - until this thread appeared. Back to the drawing board today and removed the thread sealant - amazingly the gauge now works - wonder why

[bmcecosse]

Perhaps the weather has warmed up slightly.........

[billlobban]

No its still Baltic. Still got snow in my garden (since the week before Christmas) and a two foot thick wall of ice around my roof. Still now that my temperature gauge works I can blank off a bit of the radiator to get the heater working a little better DOOH