Ok, many of you may have noticed once your RX7 warms up, the gauge goes to "Normal" and stays there. No matter what. Hot days or cold days, running hard or running easy, it doesnt seem to affect the temp gauge at all.

Recently I've read a lot of people claim they are very inacurate (Especially on the FC S5 version and the FDs).

I am wondering if first off, this is true
Second off, if it is true, I'm wondering what is at fault? The sensor, or the gauge itself?

I'm not going to make this a poll, as that would get us nowhere.

Has anyone done something that would prove either way? Such as installing an aftermarket temp gauge off of the stock water temp sensor and getting different, more widly varying readings, or vice versa?

How bout someone changing the sensor or installing a seperate sensor and getting completely different readings? (or vice versa?)

Your imput, please!

 

well, another reason for the needle staying in pretty much the same location is because some cars are special... and are equipped with something called a thermostat and radiator.

 

I dont need that kind of useless sarcastic remark. I've read a lot about people getting innacurate readings, and I'm trying to find out about it.

 

whenever mine reaches more than 1/2 of the way up, my car breaks. Seems to eb the same for everyone else, normal temp readings for the s4 are about 1/4 up the gauge, and for the s5 its 1/3 the way up. I posted somethign similar a while back and thats was normal to most people.

 

https://www.rx7club.com/showthread.p...hreadid=261350


read about 1/2 threw first page.

 

That thread is inconclusive, and this is a slightly different topic.

 

I don't think that was much of a sarcastic remark...

With all of your epuipment working correctly, your thermostat keeps the coolant temps at the "normal" reading... the "optimum" temp.

I have a S5, and everybody keeps telling me about my temp gauge being a POS. Well... it seems to work just fine for me.

Another thing I guess that helps me out, is the clutch in my fan is fuxored... so it spins ALL the time. It never shuts off. S4's are supposed to stay at 1/2 the temp gauge for "normal" operation, and S5's stay at 2/3 to half... mine never goes past half. I am however going to purchase an aftermarket temp gauge... for the fact that it's a wise investiment if my gauge does goto hell.


Not everybody's car on this forum is broke all the time Some of us luck out I guess... If your radiator and all your hoses are fine, thermostat works, proper mix of water and coolant always full... there's no real reason for your car to overheat. I have run my car hard as HELL, and it NEVER goes above half. Now what WILL **** me off is I find out with my aftermarket gauge that my car IS in fact "overheating" by a bit, and my gauge reads normal... but I'm putting my money on the fact that I don't need to worry about that. Espicially with my fan fully engaged all the time

Makes a cool sound past 5K RPM...

 

Thats exactly what I want to do, buy an aftermarket gauge. However, if as Icemark said in that thread posted above, the sender is in fact at fault, just buying a gauge wont fix it. :/

 

Correct. When I get a new gauge.. the sender unit and wires will all be replaced.

 

What are you going to replace your sender unit with?
If its an aftermarket unit, witch one?

 

OEM from mazda.

 

Icemark was saying that the OEM ones were made not to work (for the S5) not that they went bad.

 

I just read a post by Icemark.. and got me with a big smile on my face

It's not the actual GAUGE that is bad, it's the sender unit.

So when and if you buy an aftermarket gauge, be sure to get a new sender unit... BUT... If you have a S5 car, get a S4 sender unit He (Icemark) has also stated that most dealers won't carry a S4 sender unit, but finding one shouldn't be a problem off a parts car or something.

 

Only the S5 temp gauge is a "three-position" gauge. The S4's responds to changes in coolant temps as you'd expect. I also find it very hard to believe this is a function of the sender. Thermistors just aren't that complicated.

Connecting an aftermarket gauge to the stock temp sender would give you incorrect readings, as the sender and gauge have to be calibrated to work with each other.

VietFC's comment was spot on. The temp is supposed to be regulated by the thermostat and fan. Once the engine's warmed up, the temp gauge should not move at all unless the cooling system experiences a combination of engine load and ambient temp that pushes it beyond its capacity. This would indicate either a huge increase in power over stock or a problem with the cooling system due to a component failure, flow blockage, etc. The only time I've ever seen mine move above its normal position was during an uphill high-speed run with a slipping fan belt. As soon as I slowed down the temp returned to the same spot as before.

poor_red_neck, the stock fan is supposed to spin all the time. Even when cold the clutch still engaged just a little bit. To test it, try spinning the fan when the engine's completely cold. It should move with very little resistance. If it does, and you don't have any low-speed/idling cooling issues, then you have a perfectly healthy clutch.

 

Ok, I've read a lot about this so I try regurgitate it

S4's have an old school analogue guage. Meaning it shows little fluctuations in engine temp under hard driving etc.

S5's switched to a more "modern" electronic guage with three settings (most new cars are like still this)

Cold--> Normal--> You're car overheated 5 mins ago.

My S4 works just fine. In the winter at about 32 degrees F it's at 1/4 of the way. In the summer it rarely goes to 1/2 way, only if I'm going up a hill and it's 85+ degrees outside. I have a stock cooling system.

 

bump^

I want more info on this.

 

The series 4 and earlier gauge is not accurate per se, but it does move up and down with changes in ambient temp, engine load, and speed. Even if the cooling system and the car are in perfect working order, movement between 1/5 and 1/2 on the gauge is normal depending on those factors.

The s5 and FD cars used a NON LINEAR gauge. The difference is in the gauge, not the sending unit (I have used s4 sending units on s5 cars and vice versa). What non linear means is that unlike the earlier versions, these gauges do not respond to average or normal changes in temperature.

A rumor I once heard was that mazda redesigned the gauges to less accurately reflect temperature changes due to people thinking there was a problem when the gauge would naturally move, as a result of running the a/c, climbing a hill, etc.

Say for instance, on an s4 gauge, 1/4 might be 175*, 1/2 might be 200, and 2/3 might be 215. On the s5, it moves to halfway very quickly, perhaps even before coolant temp is 160*. It stays there until it exceeds a set value, probably about 215*. Only then does it move father up. Since the s4 version moves in relation to temperature all the time, and the s5 does not, the s5 is called non linear.

Bottom line, in an s5 or later, if the gauge ever moves at all above it's normal 1/2 position, something is SERIOUSLY wrong, it is getting hot quickly.

So why was that so hard to figure out?

 

OK, so I'll just pick up an aftermarket gauge.

Thats all I wanted to know, thanks Mr. Resurrection.

 

Just to add this in. With my aftermarket water temp gauge I notice this. I start the car and it warms up. It contiues to warm noticably. Until about 190....it goes to almost 200 and bam. It drops about 10F. What happened? The thermostat just opened and the the slightly cooler fluid just ran across the sensor. Does your stock gauge do that? That should say it all.

Also, your oil pressure. The stock gauge is buffered. It does not reflect the way the oil pressure is. It changes rapidly. You redline and go to idle that pressure falls like the tach. And you see that on an aftermarket gauge. You do not see that on a stock gauge.

James

 

so whats the alternative to getting an aftermarket guage?

 

If you want to accurately measure temps there isn't one.

 

I don't want to acurately measure temps.
I want to see the guage move, inotherwords, I want to see if my car is getting hotter.

 

On an s5 or later this isn't possible, the s4 gauges won't fit your car.

You're worrying needlessly. Most of the modern cars on the road use a nonlinear gauge. Keeps you from worrying about nonexistant problems. It'll be obvious if you have a cooling problem.

 

i remeber hearing something about "linearizing" the temp gauges on fds is this possible on the s5 as an option for those who want a little more info without going to an aftermarket gauge?

 

I've hit 220F before and my stock gauge was still in the exact same stop as 180. (probably the same as like 150 but don't pay attention to the stock one when it's warming up)