19 replies to this topic

[mellon87]

Hi all.

 

Having trouble wiring a smiths temperature gauge. So far what I have done is:

 

1. run a wire from the sender in the head to the gauge and connected it to the LH plug. (The side with only 1 plug)
2. Fitted a voltage regulator (TS7810CZ 1A Positive Fixed Voltage Regulator TO220 Case) from Maplin. The input side of the regulator went to a switched 12V supply on the fuse box. The centre leg to Earth and the output leg to the Gauge (RH side that has the 2 plugs)
3. The above is measuring 10.1 V on the meter at the gauge and it is stable so the regulator is working fine.
4. Any idea what the other plug should read from the sender in the head??

 

Not sure why it is not reading any temperature at all. Unless the gauge is broken but I don't think so.

 

Can anyone tell me if I have the plugs the wrong way round or what else may be stopping it showing any sort of reading. The sender is brand new.

 

Car is a 1275gt 1981 fitted with a 1300 metro engine.

 

 photo 1 (6).JPG   69.15K   44 downloads  photo 2 (6).JPG   70.39K   65 downloads

[gazza82]

The terminals appear to be marked T and B. T is probably the sender connection, B for battery.

You might not need a regulator ... Not all gauges do and is it a positive or negative earth gauge?

[mellon87]

Gaz thats the way i have them connected although with a vr.

If i try it without the vr will it damage it? Also it came with the car. Is there a way to tell if its pos or neg? Im no electrician!

Thanks for your help

[dklawson]

Gazz, thanks for your post.  I would have completely missed the T and B if you had not pointed them out.

 

The reason this gauge is not working for you is that it is NOT the type of gauge you think it is.  It is an early gauge (before 1965) that does not use the stabilizer and will not work with the later sending units.  The T and B markings were used on similar fuel gauges for MGs of the same time period (T was the "tank" sending unit wire connection and B was for the power connection to the "battery").  The second indication that this is an early gauge are those two little hex nuts on the back of the gauge.  They are used to calibrate the gauge.  This gauge will not work with the sending unit of later Minis and it does not use the voltage stabilizer.

 

I could ramble on more about the topic but I will spare you.  Suffice it to say you need a different, later temperature gauge and matching sending unit.  The back of the gauge will look like the one pictured below.   The picture is not mine, it is just what I found on the web.  HOWEVER, the picture's labeling is misleading.  It does not make any difference which terminal you connect 10V or the sending unit wire to.  They work by internal heating and are NOT polarity sensitive.  Also, ignore the text about adding resistors.  Apparently this picture came from a web site discussing how to bench calibrate the gauge.  

 

Regardless, you need a gauge that on the back looks like the one pictured below.  Sell the one you have to someone with a very early Super or Super Deluxe.

 

Edited by dklawson, 11 June 2014 - 11:04 AM.

[mellon87]

Ahhhh! now that makes some sense. !

 

Thank you for your help.. I really do appreciate it.

 

Know anyone who would like to buy the gauge and do you have a suggestion for what to replace it with so it works?

 

Cheers

[dklawson]

Were I adding a new temperature gauge and I wanted to insure that the sender matched... I would look for one from a late 1970s MGB and buy a matching sending unit.  You may have better options in Europe.

 

As for the early temperature gauge you have, it's a very special part.  I have only seen pictures of them.  Most cars from the late 1950s and early 1960s used mechanical temperature gauges.  You may want to post about this on the early Mini section of the Specialist Mini Forums.  Many of the people there want only original period parts on their cars.  

http://specialistmin...ku.com/forums/5

[mellon87]

Ok ive gone back to basics and the gauge in the cluster works. I grounded the plug and it goes straight to max temp. Im using the gtr101 sender which is for after 1969 minis. Mines 81.

What else could the problem be??

[dklawson]

I do not understand your statements and question above.

 

I thought we had eliminated the possibility of using the early gauge with the later components.  You say "what else could be the problem" but you don't say what the problem is.  Are you having trouble with the cluster temperature gauge?  If so, what is it doing or not doing?

[gazza82]

It will go to max because it is being connected directly to earth. The sender is a resistor. The cooler the water, the more resistance, the lower the gauge reads. If it goes to max with it connected to the sender, the sender is probably broken.

[mellon87]

Ok my apologies.

I first thought the gauge in the cluster was not working after buying a new sender which did not fix the problem of having no temp reading.

But the car came with a seperate smiths temp gauge as pictured so i thought id have a go at wiring it instead and believed i had to fit it with a voltage stabiliser so i bought one and wired it in instead of taking a feed from the vs on the cluster. But as you pointed out this gauge is not fit for the car and did not work.

So i then found out i could check the cluster gauge by earthing the plug on it to see if it goes to hot on the gauge. It did so now i believe the cluster gauge does work, so does the wiring, and the problem might lie elsewhere.

So could i have a faulty sender although it is brand new? (Is there a way of testing the sender??) or could there be another issue somewhere i am not noticing?

Hopefully the above makes sense now. Thanks

[gazza82]

Or it's the wrong sender ...

[mellon87]

Hence why im here asking the question...

[dklawson]

Thanks.  I understand now.

 

OK, is this a Smiths gauge cluster or a later Nippon Seiki cluster?  How is the fuel gauge performing... does it operate and appear to read correctly?  Is the temperature sender you have new or old?  Lastly, have you measured the temperature of the radiator or elsewhere on the engine to confirm that it is actually getting to temperature?

[mellon87]

It is a smiths 3 gauge cluster.

 

The fuel gauge works fine, which is confusing me even more, there was a problem with the sender in the tank but I managed to sort it and got it working.

 

The sender is new, it is a gtr101 for a 1970 onwards. But could this be the wrong sender as my engine is a 1300 metro ? engine no 12he25 or would the new sender be faulty. I have ordered a new gtr101 just in case and to help eliminate this as a problem. #The temp gauge did not work when I bought the car so im not sure if the original sender that was in the block is correct but it is different to the gtr101. The original one that was in the engine has markings on it BM1 and 6602 but im not sure what these mean nor can I find anything relating to them.

 

You can physically feel the temperature of the radiator when the car has been running a few minutes. It got the point I was concerned it may be too hot but I cant determine this until the temp gauge is sorted so I can start checking thermostats etc.

 

Thanks

[dklawson]

You said you can "feel" the heat in the engine.  If you can leave your hand on the engine/radiator, it is not at full operating temperature.  On a Smiths gauge calibrated as "C-N-H", the cold end is typically less than 100 oF, the middle of the N region is around 185 oF, and the START of the H region is right about 212 oF.  Humans typically cannot leave their hand on a surface much hotter than 150 oF so if your gauge is showing midway between C and N, and you can leave your hand on the radiator header or hoses... the engine really may just be cold and in need of a new thermostat.  I suggest buying or borrowing a thermometer or two and confirming what the engine temperature is before spending more money on parts or service. 

 

I cannot tell you what temp sending units work with what gauges.  I have yet to see a definitive list.  Regardless, it does not matter what car the engine originally came out of.  The sending unit has to match the gauge, not the original applicaition of the engine.  If your gauges are from a certain year Mini, the sending unit needs to be compatible with the same year Mini gauges. 

 

Again, find out with a thermometer (bulb type sumberged in the open radiator, thermocouple in the radiator and/or held to the t-stat housing, or infrared measuring the t-stat housing and radiator header tank) to confirm what the engine's operating temperature is.