Temperature gauge weirdness

[Mad Cow]

My temperature gauge has been inaccurate ever since I bought the car, and I always thought it was the gauge because the needle stayed in the middle when it was off instead of going to the bottom. I picked up a gas/temperature gauge assembly from a junkyard car and installed it, but now it's worse, the needle moved almost all the way to the top a few seconds after I started the car. I noticed that there was corrosion on the temp sensor connector so I soaked it in CLR to get rid of it, and now the gauge goes all the way to the top when I start it.

My gauges are either from a '94 RS or a '92 GS, I have no idea, but I'm leaning towards the GS because the ACC pin on one connector was in the wrong place, and I'm assuming the interior harness wasn't swapped out with a GS harness. I pulled the gauges from a '94+ GS, didn't check the year. On my old temp gauge, the topmost mark was red, it's white on the new one.

Could the problem be with incompatible gauges or is the sensor the problem?

[SstennizZ]

Sounds a bit like a bad mass connection.. Had that once on a aftermarket temp gauge. Don't know if that is possible on the stock one too?

[Mad Cow]

Sounds a bit like a bad mass connection.. Had that once on a aftermarket temp gauge. Don't know if that is possible on the stock one too?

What do you mean by a bad mass connection?

[SstennizZ]

Well, a aftermarket gauge has a signal wire and a mass. If the mass is bad, the gauge will give a faulty reading. Perhaps thats the case with your stock gauge..

[Mad Cow]

You mean a ground?

But anyway, I think the gauges I got are bad, today I noticed that the low gas light came on even though the gauge still said it had 1/4 left, and then I realized that the gauge hadn't moved ever since I filled it up. Gah, back to the junkyard...

[SstennizZ]

You mean a ground?

But anyway, I think the gauges I got are bad, today I noticed that the low gas light came on even though the gauge still said it had 1/4 left, and then I realized that the gauge hadn't moved ever since I filled it up. Gah, back to the junkyard...

Ow lol yeah I meant ground.. Over here we call it mass, because the circuit never touches the ground I guess..

[jeff180]

did anybody ever find out why the junkyard temp gauge goes to the roof when you turn the key on? my sensor reads nothing when the car is cold, but reads about 42 ohms when at running temp

[Newfie_dan]

there are 2 sensors for the temp reading on the v6, 1 that a single wire and thats for the dash and the other 2 wire one is for the computer or ecm/ecu. The first one for the dash simply reads resistance from the signal wire to ground, the other reads the resistance across the 2 pins. At full temp the 2 wire one should read somewhere between 1.8-1.9k ohms. The other one I have not got the exact specs on but if the gauge is not reading about half ways or lower at full temp then that sensor or wiring to it or the gauge are faulty.

[jeff180]

i'm definately hearing conflicting reports. does anybody know what the temp gauge sending unit is supposed to read when at operating temp?

[Nd4SpdSe]

[Newfie_dan]

those specs you posted are totally inaccurate for the mx-3 Nd4SpdSe this is the correct chart according to the mx-3 manuals;

[Nd4SpdSe]

That's just what Mitchell says. What I don't like it that it gives me them all for those years Mazda's, so it doesn't help to specify which ones belong to the Mx-3

[Newfie_dan]

yeah I hear ya, sometimes getting the correct info takes a little digging, I am worst off since my car is a 96 gs so I have to contend with the obd2 issue for some of my stuff, some parts differ from obd 1 to obd 2. Since they sold only in canada most parts stores are useless to me unless I get them to look it up under a 95 for my parts.

[jeff180]

ok, so to clarify, these specs are for the single-wire sensor that feeds the temp gauge? i guess i dont understand , that if it's a single-wire sensor, how you could put it in water and measure resistance. measure it against what? lol

[Nd4SpdSe]

It grounds through the metal chassis of the sensor.