Scan tool doesn't agree with gauge

[JHZR2]

Originally Posted By: ISO55000
Originally Posted By: Bladecutter
Just because you don't believe this is correct doesn't change the fact that most automotive manufacturers do what they do.

Mazda does this with just about any vehicle that has a coolant gauge (RX-8, Miata, Mazda 3, Mazda 6, etc).

Go out there, and take a look for yourself, and educate yourself.

BC.


Again, with all due respect.

I did not post a "belief" I posted a fact. Popular opinion, voting, lack of understanding et al does not alter that.

automotive manufacturers do not have their own laws of physics, secret techniques or anything else.

I don't have to go "out there" because "out there" comes to firms like mine to compute those values that go in those PFD's and P&IDs and calculate those parameters and we work out the logic based on what they want.

Hopefully I educated you now. Feel free to subject everything I have posted to any qualified authority you wish and see what they say. Then you will learn.


+1

 

[kschachn]

So the posts and threads about water wetter and other additives causing a 3-5 degree decrease in coolant temperature at operation cannot be true if they are referencing the gauge (at least in many cases)?

Apart from the whole "how does water wetter change the thermostat set point" problem, I mean.

 

[oldmaninsc]

Originally Posted By: tcp71
Not on car temp gauges. The vast majority are made to stay "centered" through a wide range of "normal" temperatures. My temp gauge in my truck stays centered from 160F on up. Never waivers right up to the highest temp i've seen on my scangauge of 221F. Thermostat is 191F. It's exactly like 4wheeldog describes.
Originally Posted By: Nate1979
Dummy gauges, like on Fords are well known that as long as the actual temp is between two values it reads on temp as perfectly normal so that the user is not questioning all the time the value. It is not averaging the value but outputting a set value as long as input is within a certain range.


Absolutely. On both of my Ford products, the gauge parks itself at about the half way point when the scan gauge is reporting from about 180F - 220F. I don't think I've ever seen either gauge go above half way. I've put over 100K miles on the Mercury and even while driving up and down the hills in the Ca. and Arizona deserts at 75 - 85 MPH on a 115 degree day the gauge never went past the half way point.

Now the gauge on my 95 Aerostar would move all over the place while driving especially while going up or down a long hill.

My 2005 Trailblazer did the same as the Fords - the gauge would sit about half way (which like many GM products was what the gauge called "210") which was actually about 165f to about 215F. I haven't tested the Impala yet, but the temperature gauge reaches the half way point in a very short time - about 1 mile of driving and stays there regardless of driving conditions.

 

[Robenstein]

Some dash gauges are just way off. I have a GM car that is WELL known for junk gauges. My gas gauge sticks, my voltage meter shows 2 volts less than actual, and my temp gauge only moves off cold when the engine is overheating.

So the only ones that are honest are the tach and speedo.

 

[JohnMack]

My 02 Le Sabre reads 129 psi of oil pressure even at idle.

 

[ISO55000]

Originally Posted By: kschachn
So the posts and threads about water wetter and other additives causing a 3-5 degree decrease in coolant temperature at operation cannot be true if they are referencing the gauge (at least in many cases)?

Apart from the whole "how does water wetter change the thermostat set point" problem, I mean.



LOL, that’s one of those subjects that galls me to no end because one of our biggest design and service areas in facility asset care is in HVAC/R and Heat Exchange (fluid and air) for industrial equipment and the building. Training people on these systems showed me real quick that most simply do not understand thermal transfer and heat exchange.

Those that do have sometimes accidently destroyed industrial systems by using those products (SCA’s [supplemental cooling additives] as called in industry) because they didn’t realize that automotive glycols and industrial glycols (both Prop & Ethy) are not the same chemistry or additive package type and are NOT interchangeable. (Not to mention an industrial system has a totally different metallurgy as well than a car cooling system)

I now teach operators and maintenance the comparison between them and explain the differences because many times they innocently read about these things and will put them in an industrial system and destroy it in short order. I blame this on the makers and sellers marketing claims because they are not lying about what these products CAN deliver (emphasis on the word can), they just don’t go into enough detail about the conditions that MUST exist in order for them to actually work. (See there’s a REASON they call these things SUPPLEMENTAL and they don’t simply replace coolants with them altogether, LOL)

This isn’t a physics class but a quick primer on what they say versus what it takes because the science behind the claims is valid but only when proper conditions exist. (Take note that the standard example is “heavy” use engines in industrial applications and race cars revving at 5K + RPM and those applications will benefit from them somewhat- the question is do those attributes exist in your application)

So the posts and threads about water wetter and other additives causing a 3-5 degree decrease in coolant temperature at operation cannot be true if they are referencing the gauge (at least in many cases)?


(I’m gonna exclude everything relating to corrosion and all that- strictly heat transfer and we aren’t talking HP closed systems like boilers, steam and nuclear)

In short these SCA’s don’t cool or transfer heat or much of anything else. Water is known as the baseline heat transfer fluid with a statistical coefficient of transfer at 1:1. All the glycols and such (recipes/mixtures and additives) basically adjust the high and low temp characteristics of the water for a given application.

What these SCA’s actually do is change the surface tension of the water which in turn affects its wetting ability which in turn makes thermal exchange a little faster.

(This few degrees lower claim they market is directly contingent on how much heat is there being transferred and the cooling system’s physical ability to cool it so even when it enables a slightly better transfer, it can overheat a system as well if the additional heat exceeds the system design delta)

How this works is high school level physics not some trade secret or magic oil.
In thermal transfer design speak on LP systems a “hot spot” is something that exceeds the boiling point of water because “hot” is relative and water is the baseline.

In a wet cylinder application there exists the following:

(which is most industrial diesels and most race cars because they use sleeve like Darton for maximum thermal exchange- remember up post where I pointed out “when proper conditions exist” so if you don’t have a wet cylinder application with a load similar to towing an aircraft carrier any reduction you get is more accident and random that deliberate and calculated)

Since part of the physical cylinder is exposed to the coolant flow, that whole are is a “hot spot”. This high delta creates a boundary layer of thermally induced cavitation between the steel and the exchange fluid. Air (conversely) is known as the worst thermal transfer medium. These SCA’s change the surface tension of the exchange fluid which makes it “wet” the area more and increases thermal transfer.

( good way to see this effect is sacrifice a pot with water in it and hit a spot with a hot torch and make it cherry- you will see this effect somewhat but not as pronounced because your pot is not a closed system under low pressure)

The down side to this (and where the advertisements are often misleading) is that if your individual engine and load do not create the thermal cavitation effect in the first place then your benefit is ZERO. (Because you already have proper surface tension and transfer when it’s not hot enough to cavitate)

OK, now we have established this is scientifically valid when the conditions exist. You still cannot and will not get any benefit unless part 2 of the thermal equation will allow for it.

(Assuming everything is working properly and spec’d properly)

It’s a heat exchange system because in the engine the mechanical heat is exchanged in the fluid- in the radiator the heat from the fluid is exchanged into the atmosphere and the cycle is complete.

This is where people often forget the 2nd law. Your witches brew SCA did not take away “more” heat or lower anything (the mass and volume of the transfer medium and system parameters determine that) the brew just allowed it to be done a wee bit faster (time).

So, if the pump flow (speed of fluid evacuation) and heat exchanger (radiator) combined with the medium of exchange (fan flow, another fluid, cooling tower etc.) HAS THE CAPACITY to accept a faster flow and the same exchange delta at that flow then you WILL see an overall reduction in operating temperature.

If not, you can see an increase in temperature.

Apart from the whole "how does water wetter change the thermostat set point" problem, I mean.


That’s an illusion and marketing claim- not a reality. A thermostat or any other balancing or diverter valve is going to open at the set point the mechanical spring (or strip) or the signal input (electronic) tells it to. In a proper application these brews change the “time” it takes the engine to get to the temp which makes you “think” it did something to the thermostat set point but in reality that’s a rain making claim.

Any HVAC/R technician, engineer or process guy who does heat transfer systems can explain this easily and this is basic stuff. There’s no magic or trade secret to it and it only works under the right conditions. This is simple physics.

 

[Bladecutter]

Originally Posted By: ISO55000
Again, with all due respect.

I did not post a "belief" I posted a fact. Popular opinion, voting, lack of understanding et al does not alter that.

automotive manufacturers do not have their own laws of physics, secret techniques or anything else.

I don't have to go "out there" because "out there" comes to firms like mine to compute those values that go in those PFD's and P&IDs and calculate those parameters and we work out the logic based on what they want.

Hopefully I educated you now. Feel free to subject everything I have posted to any qualified authority you wish and see what they say. Then you will learn.


Nope, I have gained anything new from your comment, as you didn't actually provide anything new to this topic in your response to me.

The truth of the matter is that a lot of car manufacturers supply brand new vehicles to customers that include temperature gauges that do not move until the coolant temperature hits certain ranges of temperatures. I, and many other consumers, have seen this behavior from multiple vehicles first hand for quite a while.

The temperature senders that are in the coolant stream do provide the ecu with the correct value as the coolant changes temperature, but the coolant gauge does not relay that information to the vehicle operator.

You are claiming that they do not do this, and that all automotive gauges change position with every degree of temperature fluctuation. You are incorrect in this supposition.

So, regardless if you want to claim that you were providing "facts", they are, unfortunately, incorrect, and thus, therefore are not facts.

Sometimes, actually going out into the real world, and looking at actual behavior will help you understand reality.

BC.

 

[ISO55000]

Originally Posted By: Bladecutter
Originally Posted By: ISO55000
Again, with all due respect.

I did not post a "belief" I posted a fact. Popular opinion, voting, lack of understanding et al does not alter that.

automotive manufacturers do not have their own laws of physics, secret techniques or anything else.

I don't have to go "out there" because "out there" comes to firms like mine to compute those values that go in those PFD's and P&IDs and calculate those parameters and we work out the logic based on what they want.

Hopefully I educated you now. Feel free to subject everything I have posted to any qualified authority you wish and see what they say. Then you will learn.


Nope, I have gained anything new from your comment, as you didn't actually provide anything new to this topic in your response to me.

The truth of the matter is that a lot of car manufacturers supply brand new vehicles to customers that include temperature gauges that do not move until the coolant temperature hits certain ranges of temperatures. I, and many other consumers, have seen this behavior from multiple vehicles first hand for quite a while.

The temperature senders that are in the coolant stream do provide the ecu with the correct value as the coolant changes temperature, but the coolant gauge does not relay that information to the vehicle operator.

You are claiming that they do not do this, and that all automotive gauges change position with every degree of temperature fluctuation. You are incorrect in this supposition.

So, regardless if you want to claim that you were providing "facts", they are, unfortunately, incorrect, and thus, therefore are not facts.

Sometimes, actually going out into the real world, and looking at actual behavior will help you understand reality.

BC.


That’s not nice but with all due respect I have forgotten more on this subject than you will probably know in 3 lifetimes ( and that’s being polite) because you appear to interpret what you think you see in terms of anecdotal reasoning rather than the physical science that put it there.

The “truth of the matter” is exactly what I said and I can take you to the molecular level if necessary but I digress because you are entitled to your own opinion but not your own truth and I am not here to convince you.

Here is your first error

You are claiming that they do not do this, and that all automotive gauges change position with every degree of temperature fluctuation. You are incorrect in this supposition.

Go back and read carefully. I said no such thing. (Thus the term hysteresis). I can guarantee you that if you take that gauge away from its sending unit and plug it into the test rig it will read in almost real time what the signal is. Then you can disassemble this gauge and show the “mystery buffer” that makes it hold a given range. When you don’t find that miracle part- go back and read more carefully paying strict attention to detail. You may learn something if even by accident.

Then this

So, regardless if you want to claim that you were providing "facts", they are, unfortunately, incorrect, and thus, therefore are not facts.

Negative Ghost Rider. What you need is a learning annex in thermal dynamics and instrumentation. (Might not hurt to add a course in control system design too) What you failed to do in any measure was show any factual error in anything I said. Unless that happens you have no valid point to make and I for one will be waiting with bated breath to see one.

Finally this

Sometimes, actually going out into the real world, and looking at actual behavior will help you understand reality.

Here’s reality. Over the course of 40 years I have been a part of designing, testing, building and maintaining lines and components that build a lot of things as well as complex troubleshooting that people use in everyday life. I not only live in the “real world”- this “real world” comes to our firm and those like us to do these exact things. I don’t need to understand “reality” near as much as you appear to need a fundamental education enhancement in basic science and high school level physics.

Sadly, you almost got it here but missed the mark

The temperature senders that are in the coolant stream do provide the ecu with the correct value as the coolant changes temperature, but the coolant gauge does not relay that information to the vehicle operator.

If you read and actually understood what I said, I explained this- that comment is proof you did not fully grasp it. I’m not even going to begin to go into the location selection being based on a critical metric criterion the designers calculated in because if you didn’t understand the basics you will not even be able to comprehend this.

I fully support your right to believe in whatever ghosts, goblins, conspiracy theories or mystery gauges you choose but those beliefs carry no force or weight whatsoever in the face of proven science and technology.

 

[Vikas]

How about this? Many of the factory automotive gauges in passenger cars are highly non-linear. This is easily observed when one looks at the gauge and OBD ECT PID. The graph will have a large portion of it as a flat horizontal line.

 

[supton]

Getting to be that they can just remove the temp guage, all it is now is a idiot light that does not light up. My truck has two of them engine temp and trans temp, and neither are useful. My Scanguage has to be used instead to monitor temps.

Pitiful. Such nice looking guages, but worthless.

 

[armos]

It's funny how just as cars started being widely equipped with "full gauges", those gauges turned into almost meaningless entertainment devices instead of real gauges. The ECM has the information, but manufacturers don't want to share it with the driver.
There is widespread ignorance of what normal readings should look like. The manufacturer wouldn't want their car to look worse than a competitor who uses fake readouts. They also don't want repair visits from cars which are not faulty.
Perhaps, also, there's a desire to avoid fixing legitimate problems which haven't yet reached the point where engine damage is imminent. The presumption would be that the car will usually skate past the warranty period before it happens.

Instead, the widespread strategy seems to be to show drivers what they want to see on their dashboards.
This is blatantly obvious with oil pressure gauges, which don't even remotely reflect a real mechanical reading. But it's more subtly apparent with some temperature gauges, where they will sit in the same spot while independent measurement of coolant temperature shows that it's really fluctuating significantly.

With an observant driver, an honest and preferably real-time temperature gauge can allow one to notice developing problems which can then be fixed before they reach the point of being critical. Being observant of this can save a car from it's typical old age overheating death spiral as it's cooling system degrades.
But honest gauges scare people who don't know what they're supposed to look like, so the manufacturers have shied away from sharing that info. It's disappointing, and diminishes the ability of a 2nd hand owner of an old car to keep it healthy and reliable. They won't see clues of a developing issue until a critical and inconvenient time.

 

[armos]

Originally Posted By: Robenstein
Some dash gauges are just way off. I have a GM car that is WELL known for junk gauges. My gas gauge sticks, my voltage meter shows 2 volts less than actual, and my temp gauge only moves off cold when the engine is overheating.

So the only ones that are honest are the tach and speedo.


I have the same voltmeter issue on an 86 Pontiac. In my case, it's because the needle has slipped. I saw it pop into place once, but it fell back to it's old position 2 days later.


In case you didn't already know about this:
GM had a dumb wiring error in their cars during the 80s which causes their temperature needles to slip. They sent bulb test voltage to the temperature gauge every time the cars are started. This knocks the temperature needle against the upper peg and it's pretty common for the needle to get twisted into a colder direction like you describe. On some cars it completely falls off.
If I remember correctly, the overheat light doesn't even get tested in the bulb test. They hooked it up to the wrong device. They apparently copied the same wiring flaw into most/all their cars for several years without noticing or caring about it.

Slightly later GMs seem to still have the same electrical flaw, but the gauge is damped so it doesn't slam anymore. As the starter is cranked, the needle still rises to the peg but only slowly. It would appear they "fixed" the problem by damping the gauge instead of fixing the wiring.

Other than repositioning the needle, ideally the wiring error would need to be fixed to prevent it happening again. I would guess there's articles about the best way to do that on your model but I don't know.

 

[SHOZ]

Originally Posted By: JHZR2
Ive noticed that OBD scanners don't always report the correct voltage as compared to a multimeter.


Might be the OBD reading is the ECU voltage. That's the way it is on my Hyundais.

The other gauges are just glorified idiot lights though on all the cars I've had.