8 replies to this topic

[flamenco]

Hi everyone, my 1970 mini 850 had a red temperature sender when I bought it. Just like this one..
http://cgi.ebay.co.u...1742.m153.l1262

It had a yazaki temperature guage, which used to work fine.

I then replaced the sender with a new one (as the old one broke from the bit were the guage wire attaches) and bought another red sender, and the guage didn't work. I am suspecting the sender I bought was defective.

Anyway, I then decided to buy a black temperature sender, like this one
http://cgi.ebay.co.u...1742.m153.l1262

and this time, I replaced the yazaki guage with a smiths guage (as this is the sender/guage combination I have on the other 2 minis I have, and they all read well)...however, the sender gave false readings, i.e when the water was still cold, the temperature used to rise to hot very rapidly.

When I then replaced the black sender with the red sender I had originally, and left the smiths guage, the smiths guage still scaled up to hot, but this time, instead of in a couple of seconds, it took about 15 minutes (or more) and it went up veery slowly. I now suspect that the car is really over heating and the smiths guage with the red sender is a good combination. However, before I get to buy some expensive things like a radiator and a new water pump to adress the overheating issues, I want to make sure the guage is actually reading correctly.

So, my question is, is the sender related to the brand of guage used, or the type of wiring fitted to the car?? That is, is the red sender only associated with the yazaki temperature guage, or can it be used with the smiths guage too? Or was the red sender fitted as standard to the deluxe and cooper s models up to 1969, even with smiths type of guage? Since my mini is an early 1970, it can be the case that they still fitted these same type of senders as they used to in 1969. And since the car is an 850, early mk3 850s had only the centre speedo and no water and oil pressure guages, therefore the sender and guage must have been an aftermarket modification.

by the way, the car had originally a dynamo and it has now been converted to run on an alternator.

thanks everyone in advance
Jeremy

Edited by flamenco, 23 June 2008 - 11:32 AM.

[il-barba]

what about the voltage stabiliser, would it have one?

[flamenco]

are you talking about the voltage regulator, as found on minis with a dynamo?? (if not, what is a voltage stabilizer? and where is it found?)

[dklawson]

No... he's talking about the voltage stabilizer which would be mounted on the back of a 1970's original center binnacle gauge cluster. It supplies a regulated 10V to the gauges so they operate predictably.

The Smiths temperature gauge you were talking about MUST be connected to the voltage stabilizer mentioned above. If you power the gauge directly from the fuse box it will operate with as much as 40% too much voltage. The gauge will read high and it will burn out prematurely.

You've asked a lot of questions and I'm not in a position to answer them. All I can tell you is that there are at least three different temperature sending units (maybe 4) and they only work with the gauge they were designed for. I cannot tell you what sender works with which gauges. I'm not sure anyone has the definitive answer.

A possible solution for you is to buy a temperature gauge with matching sender from another British car such as a late 1970s MGB or MG Midget. I don't think the MG line experienced the number of gauge changes the Mini did.

[flamenco]

Hi dklawson, thanks for your reply

You said that each sender is designed to work with a specific guage. I thought that too, and it is for this reason that I replaced the red sender with a black one together with a smths guage. A black sender and a smiths guage is the combination which I have on my other two minis, which were fitted as standard (one is from 1975 and the other from 1977). However, this combination didn't seem to work on this mini. Could it be maybe because I used the same connection wires from the yazaki guage?

Also, yesterday I tried the yazaki guage again and it seems to have a problem. The temperature begins to rise normally, however at about 40 degrees, the needle gives a 'kick', and either stops going up or else goes back to its original position. This happened even when I earthed the wire which goes to the sender (therefore when maximum current is flowing to the guage). The guage begins to go up, then at about 40 deg it kicks, and then continues to go up. However, this does not happen when the guage is connected to the sender (when connected to the sender, there wouldn't be enough current passing, therefore the needle does not continue to rise).

This is really confusing me, as I'm not sure whether the car is overheating or whether the sender or guage is defective.

[dklawson]

Hi. As I mentioned, I don't know what senders were designed to go with which gauges.... either by production year or by gauge number. I do know there are several senders... at least red, green, and black. I thought there was also a fourth one but I'm not certain. Anyway, I can't help you determine which is right for the gauge you have.

As I mentioned though, you do need to supply Smiths gauges with 10V from the stabilizer or they will not read correctly.

If the Yazaki gauge wire you connected to the Smiths gauge ONLY goes to the temperature sending unit... it won't make any difference to the Smiths gauge or sender. These are not special wires.

The kick you are seeing with the gauge may happen with the sender in the circuit if you suddenly took the sending unit and dipped it in boiling water to create a rapid change in the current flow through the gauge. As your engine heats up this change is rather gradual. I suspect it's a mechanical thing inside the gauge. If the gauge reads correctly once you pass through the blip I would not worry about it.

[flamenco]

I think I may have to get a new guage then, as the guage does not continue to go up (and therefore read correctly) after the kick, when it is connected to the sender. The guage goes up only if I earth the guage (and therefore cause a large current to flow through the guage). It then goes up very quickly.

[flamenco]

so solved the problem finally. Connected the black sender as per the smiths guages, and used the same yazaki connections. It still read about 40% above normal. So, I looked from where the live wire to the yazaki was coming, and it turned out it was coming from a 12V supply

So now I connected it to the 10V from the stabilizer and it now works perfectly, finally!!

thanks again guys, you're really helpful

[dklawson]

Excellent.

Thanks for posting the update.