[DIYguy]

I'd like to buy your kit if your willing to build another. In fact, I would like to buy 3 of them. I buy and sell cruzes

Hi,
I haven't ever made any kits for sale, unfortunately, just the plans.
The regulated version is the one that remains on our car and it is still working perfectly by the way.
Now there is only the occasional minor random coolant smell but absolutely nothing like it used to be.
But don't forget that I also have replaced other "problem" parts such as the water outlet manifold, the bleed hose fitting to it, the thermostat and housing, the water pump and the coolant reservoir.
The non-regulated version will work well enough and would be relatively simple (and inexpensive) to make.
Let me think about it.

On a trip back east recently I drove past the former Lordstown Assembly plant (now Foxconn).
So sad...

 

[CRUZEFLIPPER]

I'd be interested in the regulated ones too if your interested. Right now I did the chevy volt thermostat mod but it keeps me around 185°. Your method seems to be better.

 

[DIYguy]

I'd be interested in the regulated ones too if your interested. Right now I did the chevy volt thermostat mod but it keeps me around 185°. Your method seems to be better.

OK, I will see if I can source the parts at a reasonable price nowadays.
The connector to the thermostat housing is a purchased item that I can't do much about cost-wise.
The connector to the wiring harness is something that I 3D printed.
The rest of the parts including the regulator board are commercially available parts for the most part.
They don't take long to actually assemble.
The regulated version is indeed better if only because it is adjustable so that you can obtain whatever target temperature range you want.
But as mentioned in my posts and writeups, the temperature will vary slightly depending upon driving conditions.
I'll get back to you soon.

Update-
I haven't forgotten, I am still gathering component prices.
I built mine almost entirely from things I had laying around collecting dust, so my own build costs were minimal.
As a result I suspect that you may not like what I would have to ask you for them.
You'd be much better off buying the parts and either building them yourself or finding an electronics hobbyist locally to build them for you.
I will be happy to provide you a detailed list of the items, sources and their current costs if that's what you would like to do.
I could make you the 3D printed connectors for a very low cost though, as they might be the most difficult thing to source.

Further Update-
OK, I have sourced all the parts for three versions.
With only a modest charge for my time in constructing and testing them they would be as follows-
Simple version (resistor limited, no plastic enclosure) $46 each
Regulated version (with plastic enclosure) $62 each
Regulated version with voltage display (inside enclosure) $65 each
Shipping and any local sales taxes not included.
The commercial parts such as the thermostat housing connector, enclosure (as applicable), power resistors, wires, wire loom and so forth, comprise the lion's share of the price.
But I am really not in the business of building and selling such things.
I have no problem if someone else on the forum would like to do so.

The nice thing about this method is that is non-invasive and can be removed within a few minutes if you need to do so.
And on the regulated versions you can easily tune the temperature to be what you want it to be.
Just remember that the operating temperature will still vary a little depending upon the operating and weather conditions because it is a fixed bias being applied to the thermostat.

FWIW (30DEC2022)-
My modification is still working perfectly.
190-195F operation typically, few if any coolant smells any more, no codes, no issues, and the engine just generally seems happy.
If you build and try it, I think you will be pleased.
If you want to try it on the cheap (push-in connections, short wires, 6 ohm LED "tail light" resistors, and no enclosures) you should be able to do it for well under $15.
And if you don't like it, you don't even have to touch coolant to remove it.

 

[DIYguy]

Well, I see that someone has duplicated my circuit and now offers it for sale on eBay.

Thermostat control module - lower coolant temp. Astra, Insignia Cruze 1.4Turbo | eBay

Thermostat control module - lower coolant temp. Astra, Insignia Cruze 1.4Turbo | Motoryzacja: Części, Części samochodowe i akcesoria, Chłodzenia silnika | eBay!

www.ebay.pl

It doesn't bother me because I did not create it to make money personally.
However it is rather gratifying to see that someone else has independently validated the method and even made a video about it..!

Interesting that it is about $56 USD for the adjustable version shown.
So that also validates the price I estimated.
I would encourage anyone who wants to try this method of engine temperature control to just buy it from the eBay listing.

By the way, mine is still working perfectly and I have no intention to remove it, ever.
Very few if any coolant smells now, and the heater still gets toasty warm this time of year.
It works exactly as intended.

 

[andzej]

There is also second version with built-in display.

Thermostat control Module- lower coolant temperature Astra J Insignia Cruze 1.4T | eBay

Find many great new & used options and get the best deals for Thermostat control Module- lower coolant temperature Astra J Insignia Cruze 1.4T at the best online prices at eBay! Free shipping for many products!

www.ebay.com

And version without display below:

Thermostat control Module - lower coolant temperature Opel / Chevrolet 1.4Turbo | eBay

Thermostat control Module - lower coolant temperature Opel / Chevrolet 1.4Turbo | Motoryzacja: Części, Części samochodowe i akcesoria, Chłodzenia silnika | eBay!

www.ebay.pl

 

[adaniel69]

hi. what do you think about my schematic? i replaced the resistor with a relay(it consumes about 140-180ma when in use) with it's antiparallel diode and if the dc-dc converter fails, the ECU will still be able to control the thermostat directly.

i didn't tested it yet, but i will. i've tested only at home with the power supply.

View media item 272164

 

[Cruze CTRL]

Can you compile a list of the logic steps behind your circuit design ?
Example: ECU ctrl is Off (0 Volt output) => T-stat 16 Ohm heater gets n Volts to achieve 100ºC EngHT...

 

[adaniel69]

Sure.

1) if ECU control is OFF, the relay is OFF and does nothing. The thermostat is taking power from the DC-DC buck converter, 10V or whatever you set.
2) if ECU control is ON, the relay is ON and bypasses the DC-DC buck converter, giving full 12-14V to the thermostat and it opens normal. This is the case if the temperature goes too high.

I've just replaced the resistor in the original schematic(in this thread) with the coil of the relay(wich has about 70 ohm in my case). So when the coil is energized(if the coolant temperature is too high, as without this module), it bypasses our module and works as the original GM wanted.

Note: the DC-DC converter has common GND(IN-OUT) and just V+ is controlled.

 

[adaniel69]

View media item 272165

My non-professional PCB test circuit

 

[adaniel69]

I went today to test my circuit, but i have a problem. The ECU is giving pulses and the relay in my circuit is closing and opening continuous... So i have to rethink my schematic. Maybe a diode... The resistor as the original schematic and a diode...

 

[Cruze CTRL]

1. All we need is the ability to feed the t-stat heat element 1214v when we need to override the ECU.

2. The ECU needs to be fooled into thinking it's still connected to (at least?) a 15 Ohm resistance.

3. When we back off (0 Volt to the heater) the ECU must be taken off the dummy 15 ohm resistor to be re-connected with the real one (inside the thermostat) to avoid setting an error code & keep ECU control.

Can you think of a circuit to do that? (keep things simple till they work (the little steps))

FYI: The ECU verifies the 15 Ohm are present and then (in theory) feeds the t-stat voltage in 2V volt steps or so -It is called a MAP controlled t-stat, as in the graphic bellow: (It could also be doing it by timed pulses!) either way our interest in the 3 conditions above prevail.

 

[adaniel69]

1. All we need is the ability to feed the t-stat heat element 12v when we need to override the ECU.

2. The ECU needs to be fooled into thinking it's still connected to (at least?) a 15 Ohm resistance.

3. When we back off (0 Volt to the heater) the ECU must be taken off the dummy 15 ohm resistor to be re-connected with the real one (inside the thermostat) to avoid setting an error code & keep ECU control.

Can you think of a circuit to do that? (keep things simple till they work (the little steps))

FYI: The ECU verifies the 15 Ohm are present and then (in theory) feeds the t-stat voltage in 2V volt steps or so -It is called a MAP controlled t-stat, as in the graphic bellow: (It could also be doing it by timed pulses!) either way our interest in the 3 conditions above prevail. View attachment 302469

the problem is in the original schematic on this thread that ecu doens't controll the thermostat as intended. i want to correct that with my schematic. in case of high temperature on the engine, the thermostat is relying only on the buck converter, and i don't find this safe. so, i want ECU, if coolant hits 108 degree celsius, to open the thermostat as if this schematic was not installed.
so, this is my new schematic:

a14neltherm.jpg

• adaniel69
• May 17, 2023

new schematic thermostat control

i put 2 x 750ohm 5w resistor in parallel(results a 375ohm resistor) to fool the ECU and i'm using a pnp transistor to switch the signal from ECU(-) to OUT+ of the buck converter, to override the buck converter. so, if ECU want to gice full 14 volts to the thermostat, it can!!
so, the thermostat is running now with continuous voltage outputed from buck converter and pulsed 14 volts from ECU.
very simple.
i'm gonna test the schematic today in my car. on bench is working fine.

 

[Cruze CTRL]

🗿

 

[adaniel69]

Got back home from test.
First of all, i have an 80°C thermostat from Mahle(see my youtube page, same username as here, adaniel69). So, i cannot tell how is working on an original 103°C thermostat.

In my case, yes, it lowered the working temperature and with A/C on is very good i would say(2-3°C variation when driving and parked with engine on). But, without A/C, it goes to more than 90°C, i don't know exactly, maybe up to 108°C as without this modification. I didn't waited enough.
But, with the original thermostat it is an improvement, at least while driving!

The only solution here is to control the thermostat by the temperature.... Some relay/transistor controlled by the coolant temperature...

 

[Cruze CTRL]

If coolant temp rises above say 95 or 98 ºC then the RADiator fan should be engaged.. @t a low speed setting, to start with.. and see what happens IMO.
As I can charge the BATT on a daily basis, that would not present a problem.

 

[adaniel69]

ok. so, my final solution is to replace the thermostat. i've took out the core from a Mahle TM 37 80 and installed into the original Mahle 36 103(original in our engine). and for the electronic control part, i've installed in parallel with the engine temperature sensor a circuit composed by a thermal switch(60 degree celsius) in series with a 365 ohm resistor, in order to show to ECU that the temperature is higher and so is engaging the fan and opens thermostat electronically!
this way, ECU sees this:
real temparature...............ECU sees
70........................................93
72........................................94
75........................................96
77........................................97
80........................................99
82........................................100
85........................................102
88........................................104
90........................................105
93........................................108
95........................................110
all values are in degree Celsius and aproximate values!

 

[Cruze CTRL]

 

[adaniel69]

View attachment 302858

Take a look at my video regarding the core thermostat modification. I will post a video with the thermal switch and the resistor as soon as i will find time for that.

 

[DIYguy]

Lordstown the US Cruze Assembly plant (now Foxconn) is Kaput!

Yes, I drove past it last fall and it was very sad.

 

[DIYguy]

the problem is in the original schematic on this thread that ecu doens't controll the thermostat as intended. i want to correct that with my schematic. in case of high temperature on the engine, the thermostat is relying only on the buck converter, and i don't find this safe. so, i want ECU, if coolant hits 108 degree celsius, to open the thermostat as if this schematic was not installed.
so, this is my new schematic:

a14neltherm.jpg

• adaniel69
• May 17, 2023

new schematic thermostat control

i put 2 x 750ohm 5w resistor in parallel(results a 375ohm resistor) to fool the ECU and i'm using a pnp transistor to switch the signal from ECU(-) to OUT+ of the buck converter, to override the buck converter. so, if ECU want to gice full 14 volts to the thermostat, it can!!
so, the thermostat is running now with continuous voltage outputed from buck converter and pulsed 14 volts from ECU.
very simple.
i'm gonna test the schematic today in my car. on bench is working fine.

There is nothing wrong with this additional protection aspect, in fact I rather like it.
However, even if the buck converter in the electrical circuit would fail completely open the thermostat will simply open up at around 225F -235F as it would "normally".
That is unacceptably high IMHO, but entirely "normal" per the factory manuals so I don't quite buy into the idea of it providing overtemp protection.
Turning on the radiator fan earlier is a far more effective solution.
And of course you could always just make the simpler version (resistive limited) which is vanishingly unlikely to fail to begin with.

The video about changing it to use an 80C element is quite nice, thanks for making it.👍👍

FWIW-
As described in my texts, I prefer the operating temperature to be around 90C (195F) due to our local emissions laws and testing.
My car has passed testing with the modification in place and operating, so I know that it is OK and causes no harm.
With the modification my car runs very nicely in the range of 192-196F.
In fact, yesterday we drove it almost 100 miles in varying temperature conditions and it worked perfectly.