Temperature Sender Unit

[Phaeton]

Fitted a new Water temperature gauge to Matt's buggy as he didn't have a gauge. But the thread of the old sender (I think 5/8 18 found that in another forum) is completely different from the one with the gauge. Unfortunatley no converters came with it either. The gauge works, but the temperature goes up very quickly & reads over 100 when the engine clearly isn't.

So I put a meter across both senders at room temperature the new one is 1.755K ohm & in boiling water in a pan 0.145K ohm. The old one from the Mini engine read 0.771K ohm at room & 0.055K ohm at boiling. This explains why it reads high as the resistance is too low. Apart from getting an adaptor, is there any electronic way of fooling the gauge.

Alan...

 

[hmalan]

Alan,

Found what I believe to be the right size adaptor, by that I mean for converting the thread, but would need to check the internal size is right for Matt's guage and would also need his original sender so my boss can adapt as per mine.

Only problem would be how long it took, though we could post them to him.

As per previous discussion you are welcome to try mine out.

Alan T.

 

[esdebe]

My GCSE physics or was it Technology seems to say Potential difference... You may be able to do somehting by using a resiter in paralle I'll see if I can find my old notes...

 

[mines got a bonnet]

potential difference is voltage from peak to base line. you need to put a resistor in series or get the right sender

 

[esdebe]

Well, according to my calculations you will need between 1.3K and 8ohms resistor in parallel to it. I would sugest putting a 1.2K resistor in parallel and see how that effects it. it may mean that it rises quickly but the higher temperatures will read more acuratly.

Was your low reading taken at room temp ? 20degrees?

if so I would guess that at about 80 degrees the reading would be 592 ohms, and based on this you would need a resistor of 1053 Ohms so I'd go with 1K for 80 degrees to be right

Simon

 

[Phaeton]

Simon,

Not sure of your maths but what I have done is get 3x 68 Ohm resistors, put 2 in paralel & the other in series with them giving me 102 Ohms. Now at 100 degrees I have 166 Ohms across the sensor. Looks like I'm still 20 Ohms too much but ti will certainly be a little more accurate.

Alan...

 

[MattBlack]

The bush needed is 5/8UNF (Male) x M10 (female) and are available ex stock from Demon Tweeks at the not totally outragous price of £5.10.. OMG!!!