Mazda - Low coolant temp light

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Our new-to-us Mazda5 has a blue indicator light in the instrument cluster. To quote the owner's manual,
Quote:
The light illuminates continuously when the engine coolant temperature is low and turns off after the engine has reached normal operating temperature.
Does anybody know what that actually means? I would define "normal operating temperature" as the temperature at which the thermostat starts to open and therefore the coolant temperature stops increasing. However, the light goes off much sooner in a drive than the coolant temperature would have stopped increasing on either of our other two cars.
 
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My CX-5 had the same thing. I don't know the actual temperature, but it went off around the time that the heater actually started putting off halfway decent heat but doubtfully before the engine was up to full operating temp. I'd guess maybe goes off around 180f?
 
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The light is a reminder that the engine is cold and should be driven gently until it goes off, by gently I mean no redlining or stomping on the gas. Basically just drive normally till the light goes off. The light was added to remind the driver to let the engine warm up some before spirited driving. Hope this helps.
 
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They did it because after removing the temp gauge from other cars they realized it was a bad idea to give no indication to the masses about engine temperature.
 
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Wow! I haven't seen a "cold" idiot light since the 62 Olds Dynamic 88 my parents owned when I was young.
 
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The Honda Fit has such a light. My friend reports that the light goes off much sooner than he would expect. He believes the light goes out when the car goes into closed-loop operation, which can be when the coolant is still quite "cold". This sounds similar to Nick's experience above. Heat should be provided long before the coolant temperature reaches 180 deg F. Our CR-V is putting out heat before the temperature gauge comes off "C"; I'm sure the coolant temperature is still in the 100-120 deg F range.
 
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Stupid thing really is they exclude a hot engine temperature light which is far more important to a motor than cold on cars with gauges. I know our cars(Acura MDX and Subaru Legacy) are cold as the auto climate control does not blow any air out until it warms up enough.
 
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Originally Posted By: rjundi
Stupid thing really is they exclude a hot engine temperature light which is far more important to a motor than cold on cars with gauges. I know our cars(Acura MDX and Subaru Legacy) are cold as the auto climate control does not blow any air out until it warms up enough.
On my subaru its the same light it glows blue when cold and red if overheating. Off-for normal operation. My light goes off when the coolant is 140F to 150F IIRC.
 
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Originally Posted By: rjundi
Stupid thing really is they exclude a hot engine temperature light which is far more important to a motor than cold on cars with gauges.
Every car that I've been in with blue/cold coolant indicator light in lieu of a gauge has also had a red/overheat light. Our Mazda 5 has it, the NB had it, many of the rental cars I get for work have it. What cars have you been in that only had had the light for cold?
 

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I'm a real fan of BMW's variable redline on the tach. it is 4,000RPM when the engine is cold and slowly goes up to 7,000RPM when the engine oil temperature is adequately warm.
 
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Have noticed that light on some of the Mazda and Subaru rentals I've had. Not sure I'm a fan. Feels like they're dumbing it down for consumers. Perhaps some focus groups revealed that people don't like the cluttered cluster? My M3 doesn't have coolant temp, but does have an oil temp gauge. It also has the "moving redline" as OVERKILL mentioned.
 
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Our Honda eschews the full gauge, but doesn't go all the way to just a light. It's got a bar graph in the center information display. This is a very slick implementation to me...it keeps real estate to a minimum, but still transmits as much information as a needle gauge would do.
 
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Originally Posted By: dparm
Feels like they're dumbing it down for consumers.
Most cars with a "coolant temperature gauge" have been nothing but analog idiot lights for over a decade now. It's certainly simpler just having two lights. Those of us that actually want to know the true temperature will do so with a ScanGauge, UltraGauge, Torque or Rev regardless of what the dash tells us or not.
 
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Coolant temp varies wildly within the engine. The bulk of the coolant in the radiator can still be quite cool while the cylinder head coolant may be at or very near normal operating temps. This is more exaggerated in larger cooling systems but applies to almost anything with a thermostat. In order to evaluate a temperature reading you must first know where on or in the cooling system it was taken...
 
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My Mazda3 has that same blue/red light setup. I am not a big fan, but I liked the car so I deal with it. I read in a technical publication somewhere that the blue light goes off at 173°F. Using my OBDII scan tool I confirmed that, of course, not knowing for sure where the temperature reading is being taken. The strategy Mazda employs to get the car to operating temp quickly (accompanied by the short-duration raucous sound of the Skyactiv engine) seems to be effective. Though, I am in Texas and my car is garaged.
 

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Originally Posted By: SteveSRT8
Coolant temp varies wildly within the engine. The bulk of the coolant in the radiator can still be quite cool while the cylinder head coolant may be at or very near normal operating temps. This is more exaggerated in larger cooling systems but applies to almost anything with a thermostat. In order to evaluate a temperature reading you must first know where on or in the cooling system it was taken...
Where are coolant thermometers normally located? On my Cobalt, there's an actual degrees-Fahrenheit temperature readout. It usually stabilizes at around 187 degrees, but in conditions where airflow is low, it can be 195 to 210.
 

NateDN10

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Originally Posted By: DBMaster
My Mazda3 has that same blue/red light setup. I am not a big fan, but I liked the car so I deal with it. I read in a technical publication somewhere that the blue light goes off at 173°F. Using my OBDII scan tool I confirmed that, of course, not knowing for sure where the temperature reading is being taken. The strategy Mazda employs to get the car to operating temp quickly (accompanied by the short-duration raucous sound of the Skyactiv engine) seems to be effective. Though, I am in Texas and my car is garaged.
Thanks. This is the first time I've seen an actual temperature listed. Our Mazda5 has the 2.5L MZR engine and not the SkyActiv one... I wonder if it's the same.
 
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Coolant temp is usually from a water jacket in the head. So it's "inside" the thermostat loop. This is the closest the computer can get to the intake manifold and how it's atomizing the incoming fuel... and if it has to enrich for cold conditions. I had a mazda b2000 pickup, carbureted, that had a sensor in the radiator of all places. Below 65'F it ran some sort of choke heater. I wired up my own "cold light" to this for my own amusement. I rented a corolla that shifted 1-2 at 3500 RPM at WOT when cold. I could see a cold light combined with throttle by wire to tell the driver that maximum acelleration will not be available.
 
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My '13 Mazdaspeed 3 is the same way on cold starts: soon as it fires up it revs to around 1800 rpm then settles down to about 1100 after about 15 seconds. Kinda unnerving but the owners manual states this is done to get the catalysts up to temp quickly. Wouldn't want to run a straight 40 weight in that car....
 
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