Temperature gauge reading high (sort of)

[Icedmunkie]

I am wondering if anybody can help...

As you know I have fitted a Mazda MX5 engine and box to my Firenza but I know have an issue with temperature gauge of sorts. The gauge reads fine but it says its too hot, which would be true if the temperature was this hot with the original 1256 engine, however MX5's run a lot hotter with 87-93 Celsius being the optimum temperature.

What I am asking is if anybody knows how to get the target temperature of 87-93 to sit in the middle of the gauge, so that when it goes hotter than this it moves to hot?

It might not be possible but I was hoping not to have any extra gauges unless I really have to have any.

Car is currently using a 3 wire temperature sender from the MX5 with two wires going to the ECU which gives me a digital output on the laptop and the third wire goes to the gauge.

Chris

[droopsnoot]

Some kind of resistor in line from the third wire to the gauge would seem to be the way to sort it out. Exactly what value of resistor is anyone's guess, though it's probably a calculation based on the standard running temperature of an OHV engine vs. the standard running temperature of your MX5 engine.

[1972nail]

This may be a solution.

https://www.carbuilder.com/uk/multi-gau ... o4QAvD_BwE

[brading]

Connect as diagram changing fuel gauge for temp gauge. Adjust potentiometer till you get the reading you want then check the Ohms reading between A and B terminal with a multimeter. Now you know what size resistor to put in the line to get the reading you want.

[droopsnoot]

That diagram suggests three connections on the fuel gauge, I'm not familiar with anything other than the seven dial dash, but that only has two - one from 12v off the voltage regulator, and the other direct from the sender.

[brading]

I just put the earth in like that clarification. If the gauge is earthed they usually does it through the body.

[Fred Dukes]

The instrument cluster is powered via a Voltage stabiliser mounted on the back of the cluster - if you are connecting direct to the battery ( higher voltage than the stabiliser o/p) for your check will it effect the value of the resister you need

[Fred Dukes]

The instrument cluster is powered via a Voltage stabiliser mounted on the back of the cluster - if you are connecting direct to the battery ( higher voltage than the stabiliser o/p) for your check will it effect the value of the resister you need

[droopsnoot]

I just put the earth in like that clarification. If the gauge is earthed they usually does it through the body.

Certainly on the seven-dial dash, the only connection to earth is via the fuel tank sender unit. The instrument panel itself is plastic, so there's no other earthing present.

The instrument cluster is powered via a Voltage stabiliser mounted on the back of the cluster - if you are connecting direct to the battery ( higher voltage than the stabiliser o/p) for your check will it effect the value of the resister you need

I would think the thing to do would be to use the output from the voltage regulator where the diagram says "Ignition terminal".

[Icedmunkie]

Connect as diagram changing fuel gauge for temp gauge. Adjust potentiometer till you get the reading you want then check the Ohms reading between A and B terminal with a multimeter. Now you know what size resistor to put in the line to get the reading you want.

Gauge Check.jpg

I am assuming that this link will do the job in adjusting it?
https://www.carbuilder.com/uk/multi-gau ... o4QAvD_BwE

Thanks for the diagram