Hi again all,

My water temperature gauge is absolutely all over the place. It'll go up to half just when i turn the ignition on and will then continue to fluctuate all over the place, on a completely cold engine. Sometimes it'll go to the max on the scale and just stay there.

Obviously it's showing the wrong readings. What's likely to be wrong here and need replacing? i'm presuming the gauge should be ok and it needs some sort of sensor?

I've seen posts on thermosensors, thermoswitches and thermostats! Any of them what's needed? Or are all of those suggestions completely wrong! These three are confusing me now!

 

Sender for the water temp gauge is on the driver side of the block, under the oil filter pedestal. I may be shorting out somewhere in that area. Perform a check of the wiring and report back


Later

 

It's a UK RX7 so right hand drive btw... just thinking it may be somewhere else on mine? As the oil filter is over on the right as you look at it from the front...
Just a thought...

 

Well get off the computer and go out and look for the single wire in that area....on both sides !



LAter

 

It's dark! And I don't know what single wire I'm looking for! :P But I'll have a look first thing tomorrow and let you know!

 

It won't matter whether it's RHD or LHD. It's a single wire lead, and the sensor has a male spade connection. IIRC, it's actually just infront of the oil filter pedestal but on the rear iron. Remove the intake elbow and it should be alot more accessible from above. But easiest to see from below.

Not a good picture, but the best I can do. Small sensor you can just barely see in the circle:

 

Ahh I see what you mean by that now, I thought you meant the wire colser to the point where it would be going though the firewall, hence thinking it could be different as my gauges are on the right!

Anyway I've found the wire and the connection looks fine. sprayed some WD40 on it for good measure but it's still going up and down on completely cold engine.

A point of note, when I removed the wire completely and turned the ignition on, the gauge in the car was still going up and down... suggesting a problem along the wireing rather than the temp. sender itself?

 

Your problem may be in the instrument cluster or the wire may be grounding intermittently. By the way, make sure you removed the correct wire. There are two single wires there, the oil pressure sender and the temp sender. The oil pressure sender is the large mushroom coming out of the block and the temp sender is a little, tiny, easy-to-miss sensor that threads into the rear iron just in front of the oil pressure sender. Its connector requires you to depress a little locking tab to release, while the oil pressure sender slides laterally to engage with a T pin.

 

have you disconnected the instrument cluster for anything? If so, it may be the flex print connectors not making proper contact to the instrument cluster. Other options are the gauge itself on the cluster or a chafed wire.

 

All fixed! it was just as simple as fiddling with a few connections behind the dash and making sure they were all as they should be!

Thanks for all the help everyone! Turned out to be nice and simple

 

Now to throw a wrench in the works... I suggest that you read up on the stock temperature gauge. The general consensus seems to be that since they are not linear, you should either install an aftermarket water temp gauge, or perform a bit of surgery on the stock gauge so that it reads more accurately. Do a search for temp gauge linearization and see what you find.

 

Already on it I've been doing some reading about how inaccurate it is! Makes you wonder why Mazda designed it that/put it in the car like that in the first place, especially as cooling on thee cars seems so important!!

Thanks for the advice, it's going to be the next thing on the list to do after the belts are done!

 

The reason it was calibrated like that (and a great majority of cars now do it similarly) is so the "average" owner does not see and get upset about normal temperature fluctuations. Unfortunately, this leads to having little or no warning that the cooling system may be having a problem. In most cars, no big deal. In the FD, VERY big deal. I did the "linearization" on mine. It works very well.