[adaniel69]

@DIYguy the problem with the 80°C thermostat is when the engine is running but the car is not moving(ex. On traffic light, waiting for somebody...). In this situation, coolant goes up to 108°C, until ECU sends command to open the thermostat electronic and starts the fan. As long as the car is moving, the temperature is about 80°C. So, to avoid this, i installed in parallel with the engine coolant temperature sensor a 365 ohm resistor that kicks in when the engine has reached a certain temperature(thermal switch). This way, when the engine has reached about 93°C(real), over OBD i see 108°C and the fan is starting and thermostat opens electronic!
I will post some videos on my YT channel with the same username as here.
👍

PS: you have to understand that this thermostat is working mechanically(partial opened, even when more than 100°C) and electronic(fully opened(even on 0°C).
Even with the 80°C thermostat, without the electronic part, coolant can boil(>108°C)!

 

[DIYguy]

@DIYguy the problem with the 80°C thermostat is when the engine is running but the car is not moving(ex. On traffic light, waiting for somebody...). In this situation, coolant goes up to 108°C, until ECU sends command to open the thermostat electronic and starts the fan. As long as the car is moving, the temperature is about 80°C. So, to avoid this, i installed in parallel with the engine coolant temperature sensor a 365 ohm resistor that kicks in when the engine has reached a certain temperature(thermal switch). This way, when the engine has reached about 93°C(real), over OBD i see 108°C and the fan is starting and thermostat opens electronic!
I will post some videos on my YT channel with the same username as here.
👍

PS: you have to understand that this thermostat is working mechanically(partial opened, even when more than 100°C) and electronic(fully opened(even on 0°C).
Even with the 80°C thermostat, without the electronic part, coolant can boil(>108°C)!

I am very well aware of how the cooling system and ECM control algorithm works, thanks.
I must point out that you are incorrect or at least a bit misleading about it being able to electronically open at 0°C.
If powered on at full battery voltage the stock thermostat will open at about 76°C per the FSM and many other sources, not 0°C. Sorry, it just is.
The reason the temperature continues to rise despite having an 80°C thermostat is because the radiator fan is off and there is a lack of airflow through the radiator.

If the water exiting the radiator is at the same temperature (or higher) than the thermostat's setpoint, no matter what it may open at it is physically impossible for the water to cool the engine.
This is thermal physics in action, a basic law of nature, and is how the Cruze cooling system works, unfortunately.

I have even written about the fact that the aero shutters on some cars (mine for example) will happily choke off the radiator airflow even at highway speeds until the engine is running at 108C, and this is 100% by design.
You could literally remove the wax motor element from the thermostat entirely and it would still run that hot at a long stoplight because only about then would the fan turn on.

However you get the fan to turn on earlier is up to you, but as long as you can make it happen, it will work well.

I and several hundred other people have proved this concept beyond any doubt on another car type that had a disgustingly similar coolant temperature control scheme (Saturn).
It exhibited almost identically the same behavior (gee thanks GM...).

Adjusting the thermostat downward is a part of the solution, but it is emphatically not the whole solution.
As long as your switched resistor solution does not set codes or run afoul of emissions monitoring, go for it...
Sounds like an interesting idea actually.
However I can tell you (because I tried it) that leaving a resistor in place all the time (not switched) WILL set error codes ("improbable temperature").
So if switching in at a certain temperature and not before does the trick, more power to you.

 

[raforr]

@DIYguy the problem with the 80°C thermostat is when the engine is running but the car is not moving(ex. On traffic light, waiting for somebody...). In this situation, coolant goes up to 108°C, until ECU sends command to open the thermostat electronic and starts the fan. As long as the car is moving, the temperature is about 80°C. So, to avoid this, i installed in parallel with the engine coolant temperature sensor a 365 ohm resistor that kicks in when the engine has reached a certain temperature(thermal switch). This way, when the engine has reached about 93°C(real), over OBD i see 108°C and the fan is starting and thermostat opens electronic!
I will post some videos on my YT channel with the same username as here.
👍

PS: you have to understand that this thermostat is working mechanically(partial opened, even when more than 100°C) and electronic(fully opened(even on 0°C).
Even with the 80°C thermostat, without the electronic part, coolant can boil(>108°C)!

Hi adaniel,
Your solution could solve my problem as well, I have a 2016 Chevy Sonic LTZ (uses same cruze engine), as it was overheating, I changed the 105 C thermostat to 80°C thermostat and now its ok but I have realized P0128 code appears sometimes, this code refers to "coolant temperature below thermostat regulating temperature" and occurs when I am in a freeway and the average temperature is between 75 to 81 °C (too cold too long).

The problem is that when the ECU sends the code p0128 then the FAN starts working at its max speed and the A/C stops working, could be an ECU protection mechanism but for some reason when this error code appears the A/C compressor does not start until I erase the code with an odb scanner...

Looking forward to your video on your channel.
RR

 

[DIYguy]

Hi adaniel,
Your solution could solve my problem as well, I have a 2016 Chevy Sonic LTZ (uses same cruze engine), as it was overheating, I changed the 105 C thermostat to 80°C thermostat and now its ok but I have realized P0128 code appears sometimes, this code refers to "coolant temperature below thermostat regulating temperature" and occurs when I am in a freeway and the average temperature is between 75 to 81 °C (too cold too long).

The problem is that when the ECU sends the code p0128 then the FAN starts working at its max speed and the A/C stops working, could be an ECU protection mechanism but for some reason when this error code appears the A/C compressor does not start until I erase the code with an odb scanner...

Looking forward to your video on your channel.
RR

That is one of the reasons I designed my setup to run at about 95°C and not at 80°C or lower.
You need to stay somewhere in the middle of the "normal" operating range according to the ECU.
But it really is necessary to start the radiator fan up at a lower temperature than that l if you want it to be rock steady.
The fan should (in my experience) start running when the radiator outlet water temperature gets to about 70°C-75°C and shut off when it drops to around 60°C.
That way the thermostat will have a source of coolant that is reliably lower in temperature than its own set point so it can do its job properly.
This is exactly what I did on the Saturn using an external fan controller set to 70°C.
The situation went from the engine temperature cycling between about 95°C (the thermostat set point) up to around 105°C-110°C (gasp..!) all the time.
Does that sound a little familiar?
After adding in the external fan controller it was rock steady at around 95°C all the time and I just stopped worrying about the temperature after that.
I put almost 200,000 miles on that car with that setup installed and it never, ever got hot or overheated again.
Hundreds of people on the Saturn forum did the same thing and all had the same good results.
So it really, really, works...
FWIW.

 

[adaniel69]

@raforr i didn't had P0128 or any other code after switching to 80°C element. But, i think, with what i've explained(switched resistor in parallel with engine temperature sensor), you could get rid of that fault code, because ECU sees about the right temperature. Also, i cut a little bit from the rod of the heating element(about 1.5mm), to rise the temperature a little bit!

@DIYguy yes, you're right! Fan is important to run while the car is standing still with engine on. I'm happy with my modification. Of course, better is to reflash ECU with a modified software... I don't want to controll the fan external because it's more complicated than my solution. Anyway, i need to test it on longer trips. This is why i'm not posting it yet on my YT channel.
PS: with 0°C, i mean outside temperature, not water temperature

 

[OBD]

Hi to eveyone!

I am thinking about making this mod to my car. Have everything ready, but i concern about what will happend if the voltage regulator fails. Is you get no voltage on the thermostat, will this make the temperature raise too high?.

Thanks!

 

[adaniel69]

Hi to eveyone!

I am thinking about making this mod to my car. Have everything ready, but i concern about what will happend if the voltage regulator fails. Is you get no voltage on the thermostat, will this make the temperature raise too high?.

Thanks!

Hi. I don't recommend you this mod(the one on the original post)! For me, it didn't work.
instead, i've switched the thermostat with a 80°C one(and cut 1,5mm from the central pin) and connected a resistor in parallel to the temperature sensor. The resistor is connected via a thermal switch.

 

[OBD]

Hi. I don't recommend you this mod(the one on the original post)! For me, it didn't work.
instead, i've switched the thermostat with a 80°C one(and cut 1,5mm from the central pin) and connected a resistor in parallel to the temperature sensor. The resistor is connected via a thermal switch.

I will give it a shot. It's more easy to fit this electronically, than changing the thermostat. I am just concerning about what will happend if the voltage regulator fails. Will the engine overheat, or will keep in "safe" values?

Thanks!

 

[adaniel69]

I will give it a shot. It's more easy to fit this electronically, than changing the thermostat. I am just concerning about what will happend if the voltage regulator fails. Will the engine overheat, or will keep in "safe" values?

Thanks!

Like i told you, for me, it didn't work! The problem is that ECU cannot control the thermostat anymore with this "mod". Engine can overheat!

You can test a 365 ohm resistor in parallel to the temperature sensor and a manual switch. Switch on when coolant is over 70°C and see what happens. Fan is engaging at about 90°C real and ECU will see about 108°C!
A resistor is cheaper.

 

[andzej]

Like i told you, for me, it didn't work! The problem is that ECU cannot control the thermostat anymore with this "mod". Engine can overheat!

What are You talking about...🤦‍♂️
Apart from the fact that ECU in 1.4t engines unfortunately very rarely turn on the heater, if the module somehow failed or the thermostat's heater was damaged (which can happen even without using the module, but still very unlikely), the thermostat will automatically open manually at the temperature specified for the exact thermostat, after which the fan will turn on (just like without using the module) and reduce coolant temp.
The fact that it didn't work for you means you did something wrong.

 

[adaniel69]

What are You talking about...🤦‍♂️
Apart from the fact that ECU in 1.4t engines unfortunately very rarely turn on the heater, if the module somehow failed or the thermostat's heater was damaged (which can happen even without using the module, but still very unlikely), the thermostat will automatically open manually at the temperature specified for the exact thermostat, after which the fan will turn on (just like without using the module) and reduce coolant temp.
The fact that it didn't work for you means you did something wrong.

I've tested the thermostat even on the table(home)! With 10 volts, continuous, it doesn't open at all!!
The problem on these engines is that the fan helps to cool the engine. But the fan is engaging at 108-109°C...
So, by fooling ECU that the temperature is higher than it actually is(example: real 95 but ECU sees 108), it turns on the fan and the thermostate! This is better, compared with original post!

Is my opinion.
I'm not trying to convince anyone wich method is better... I'm just saying that feeding the resistor in the thermostat with 10 volt continuous, it does nothing!(Again, tested! In the car and on the table)
I'm not selling anything...

Try it yourself, with the termostate on the table!

 

[andzej]

I've tested the thermostat even on the table(home)! With 10 volts, continuous, it doesn't open at all!
(...)
I'm just saying that feeding the resistor in the thermostat with 10 volt continuous, it does nothing!

At what water temp? Or maybe you did test "on dry"?
For some people, depend on the thermostat they have, even ~9.0-9,5 Volts is enough to get the temperature of 90-95℃. Maybe you have some bad thermostat.
I've had plenty of feedback and no one has been dissatisfied yet, sorry..

 

[adaniel69]

At what water temp? Or maybe you did test "on dry"?
For some people, depend on the thermostat they have, even ~9.0-9,5 Volts is enough to get the temperature of 90-95℃. Maybe you have some bad thermostat.
I've had plenty of feedback and no one has been dissatisfied yet, sorry..

Ok. I will use my modification. I'm happy with it!
My fan is turning on at about 93-94°C real and ECU sees 108-109°C. Normal driving 80-85°C, ECU sees 99-102°C. ECU cannot complain.
I don't want to argue with anyone.
You can sell your product further!

 

[Arief99]

I am very well aware of how the cooling system and ECM control algorithm works, thanks.
I must point out that you are incorrect or at least a bit misleading about it being able to electronically open at 0°C.
If powered on at full battery voltage the stock thermostat will open at about 76°C per the FSM and many other sources, not 0°C. Sorry, it just is.
The reason the temperature continues to rise despite having an 80°C thermostat is because the radiator fan is off and there is a lack of airflow through the radiator.

If the water exiting the radiator is at the same temperature (or higher) than the thermostat's setpoint, no matter what it may open at it is physically impossible for the water to cool the engine.
This is thermal physics in action, a basic law of nature, and is how the Cruze cooling system works, unfortunately.

I have even written about the fact that the aero shutters on some cars (mine for example) will happily choke off the radiator airflow even at highway speeds until the engine is running at 108C, and this is 100% by design.
You could literally remove the wax motor element from the thermostat entirely and it would still run that hot at a long stoplight because only about then would the fan turn on.

However you get the fan to turn on earlier is up to you, but as long as you can make it happen, it will work well.

I and several hundred other people have proved this concept beyond any doubt on another car type that had a disgustingly similar coolant temperature control scheme (Saturn).
It exhibited almost identically the same behavior (gee thanks GM...).

Adjusting the thermostat downward is a part of the solution, but it is emphatically not the whole solution.
As long as your switched resistor solution does not set codes or run afoul of emissions monitoring, go for it...
Sounds like an interesting idea actually.
However I can tell you (because I tried it) that leaving a resistor in place all the time (not switched) WILL set error codes ("improbable temperature").
So if switching in at a certain temperature and not before does the trick, more power to you.

Hi,
i am from Indonesia, i have same problem with you , with my chevrolet trax, i am already try to make modification as you share the wiring, i am use with voltage regulator and 360 ohm 1 watt 1 %,no dtc,but when i am try, the thermostat still not open on the temperature i want
i set the voltage 11volt, but if i check with my scanner, thermostat command still not open, what i am wrong?
i want to ask, if we give the voltage will open, but how we know if it will open at temperature we set?

Thank you

 

[Cruze CTRL]

Ok. I will use my modification. I'm happy with it!
My fan is turning on at about 93-94°C real and ECU sees 108-109°C.
Normal driving 80-85°C, ECU sees 99-102°C. ECU cannot complain[?].
I don't want to argue with anyone. You can sell your product further!

B. A -15% lower temp ideal for:
1. Heavy traffic stop and go,
2. Traffic lights, Stop & Start,
3. Overtaking, on-ramp, traffic merging prep (yeah that exists)!
4. Uphill high-gear speed holding,
5. Mountain climbing (even HS highway uphill).

Other CS temps should be:
A. (0%) Highway economy mode,
C. (-10%) Light traffic / cruising,
D. (-20%) Towing, Loaded or racing uphill,
E. (-30%) Just before parking (lowering turbo, oil & coolant temps +CS pressure).

I -Digital temp sensor at coolant recirculation hose.
II -Alarm on the digital gauge, beeping & putting fan on high speed.
III -Dash POT to adjust resistance to fool the ECU on doing or setup.

*POT potentiometer (Manually adjustable variable resistor)

 

[daniel.agape]

Hi, i am from Indonesia, i have same problem with you , with my chevrolet trax, i am already try to make modification as you share the wiring, i am use with voltage regulator and 360 ohm 1 watt 1 %,no dtc,but when i am try, the thermostat still not open on the temperature i want i set the voltage 11volt, but if i check with my scanner, thermostat command still not open, what i am wrong? i want to ask, if we give the voltage will open, but how we know if it will open at temperature we set? Thank you

Hi. This schematic didn't worked for me! Check my youtube channel(adaniel69). I've replaced the thermostat core(with a 80°C one) and put a 365 ohm resistor in parallel with the engine temperature sensor after 6 minutes of engine run. You can connect the resistor manually(via a switch) or put a time relay(like i did).

 

[Arief99]

Hi, update from me, it schema work, i am using with regulator, but i am set at 7,5volt because if set at 10volt,the temperature steady at 77,now the temperature steady at 87-88,any idea why my car just need 7,5volt?

 

[Cruze CTRL]

☹

 

[Arief99]

Apples & Onions 😄

What means apples and onions?

 

[Cruze CTRL]

🍒