# Questions about wires



## RuinedCruze (Mar 30, 2020)

So i have a corroded connector on my 1.4 cruze (the one the plugs into the too of the thermostat). Its throwing codes for high voltage and overheating. I gutted the thermostat for a quick fix, as the car is my daily and i need to get to work but im now looking at buying a new wiring harness/connector (not sure if i wanna splice and replace the whole wire or depin the connectors, as ive never worked on automotive electrical so im just looking for the easiest solution) im seeing different types of hvac wiring (with/without climate control??)and connectors and im unsure of what kind/style i need for the thermostat.


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## Blasirl (Mar 31, 2015)

RuinedCruze said:


> So i have a corroded connector on my 1.4 cruze (the one the plugs into the too of the thermostat). Its throwing codes for high voltage and overheating. I gutted the thermostat for a quick fix, as the car is my daily and i need to get to work but im now looking at buying a new wiring harness/connector (not sure if i wanna splice and replace the whole wire or depin the connectors, as ive never worked on automotive electrical so im just looking for the easiest solution) im seeing different types of hvac wiring (with/without climate control??)and connectors and im unsure of what kind/style i need for the thermostat.


Welcome Aboard!

Can you post the codes.

Don't forget to introduce yourself and your Cruze here.


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## plano-doug (Jul 1, 2015)

RuinedCruze said:


> So i have a corroded connector on my 1.4 cruze (the one the plugs into the too of the thermostat). Its throwing codes for high voltage and overheating. I gutted the thermostat for a quick fix, as the car is my daily and i need to get to work but im now looking at buying a new wiring harness/connector (not sure if i wanna splice and replace the whole wire or depin the connectors, as ive never worked on automotive electrical so im just looking for the easiest solution) im seeing different types of hvac wiring (with/without climate control??)and connectors and im unsure of what kind/style i need for the thermostat.


I think there are two connections there, one for the temp sensor, and one for the heating element. Sometimes, you can buy new pigtails and splice them in, but when I looked just now for the temp sensor pigtail, there were slim pickings - none at Autozone, and two pricey ones - $26 each - at Rockauto. I didn't look for the heating element connector.

If it is indeed the temp sensor, the one concern I have is getting the right contact plating, if that matters. Of the two underhood temp sensors, I believe the only difference in them is the contact plating - one of them has more expensive plating. Not sure if that's for reliability, or perhaps some other effect. But that could imply different contact plating on the mating connector as well. So that may be a consideration in selecting a new pigtail.

If you could cut one off a junk yard car and splice it in, that may be the simplest solution, but most salvage yards don't like that - they want to sell the entire harness, intact.

If you can nail down whether it's the heating element or sensor, perhaps a trip to the dealer parts counter will be fruitful. If they by chance offer a pigtail, it may be pricey, but it will be the right part.

HTH.

Doug

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## RuinedCruze (Mar 30, 2020)

plano-doug said:


> I think there are two connections there, one for the temp sensor, and one for the heating element.  Sometimes, you can buy new pigtails and splice them in, but when I looked just now for the temp sensor pigtail, there were slim pickings - none at Autozone, and two pricey ones - $26 each - at Rockauto. I didn't look for the heating element connector.
> 
> If it is indeed the temp sensor, the one concern I have is getting the right contact plating, if that matters. Of the two underhood temp sensors, I believe the only difference in them is the contact plating - one of them has more expensive plating. Not sure if that's for reliability, or perhaps some other effect. But that could imply different contact plating on the mating connector as well. So that may be a consideration in selecting a new pigtail.
> 
> ...


Thanks, super helpful information there. Im not sure if its the temp sensor or the heating element but i can see that the corrosion is in the connector that plugs in the top of the thermostat housing. Ive already tried all the scrap yards in my area and nobody wants to let me in to start cutting wires lol. I saw a couple connectors with tails online (they were pricey but im at the point of not caring) but im insure of what i need. They have some with climate control, and some without. Im unsure of what that means so its difficult to find the right part.


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## RuinedCruze (Mar 30, 2020)

RuinedCruze said:


> Thanks, super helpful information there. Im not sure if its the temp sensor or the heating element but i can see that the corrosion is in the connector that plugs in the top of the thermostat housing. Ive already tried all the scrap yards in my area and nobody wants to let me in to start cutting wires lol. I saw a couple connectors with tails online (they were pricey but im at the point of not caring) but im insure of what i need. They have some with climate control, and some without. Im unsure of what that means so its difficult to find the right part.
> 
> Also here is the code it was throwing (along with a p00B6 but thats gone due to me gutting the thermostat)


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## plano-doug (Jul 1, 2015)

RuinedCruze said:


> Thanks, super helpful information there. Im not sure if its the temp sensor or the heating element but i can see that the corrosion is in the connector that plugs in the top of the thermostat housing. Ive already tried all the scrap yards in my area and nobody wants to let me in to start cutting wires lol. I saw a couple connectors with tails online (they were pricey but im at the point of not caring) but im insure of what i need. They have some with climate control, and some without. Im unsure of what that means so its difficult to find the right part.


Reading some more on the 1.4T, one coolant temp sensor is on the driver's end of the motor, at the water outlet (same as on the 1.8). So the connector on the thermostat housing (on the passenger end of the motor, different than the 1.8) must be for the thermostat heater. (With the second coolant temp sensor on the radiator, on both the 1.4 and the 1.8.)

I'm struggling to find a mating connector for the thermostat heater. There may be one out there, but it will take some more digging.

Rather than replace the connector, another solution may be to bypass it. Solder two wires to the contacts at the thermostat housing, then solder the other ends to the wires feeding the corroded connector (after you cut it off). Be sure to maintain the correct polarities. You may need to use a hot knife to cut back some of the plastic housing around the contacts - I wasn't able to find a clear pic of them on the web.

No doubt, that's a ******* hack, but if done correctly, it can provide a reliable solution. The downside is that, should the thermostat housing need replacing, the wires will need to be de-soldered and re-soldered. Or maybe by that time, a suitable connector/pigtail will be available.

I do wonder how your connector became so corroded. Perhaps there was an earlier coolant leak nearby which affected it. Or maybe the rubber seal in it fell out when it was previously removed for some work leaving it exposed to the elements.

Anyway, I've had decent luck replacing various connectors like this, but this one seems to be pretty scarce.

Doug

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## RuinedCruze (Mar 30, 2020)

plano-doug said:


> Reading some more on the 1.4T, one coolant temp sensor is on the driver's end of the motor, at the water outlet (same as on the 1.8). So the connector on the thermostat housing (on the passenger end of the motor, different than the 1.8) must be for the thermostat heater. (With the second coolant temp sensor on the radiator, on both the 1.4 and the 1.8.)
> 
> I'm struggling to find a mating connector for the thermostat heater. There may be one out there, but it will take some more digging.
> 
> ...


I had replaced the thermostat around August 2019, because of the symptoms i just bought & replaced the part with out looking first. When i got it off i noticed the corrosion along with some cracks in the plastic housing near the connector so perhaps thats how it got corroded. I appreciate the idea & Ill have to do some more research on soldering but for the work required i think i would much rather fix it the proper way if thats an option. I replaced the two coolant temp sensors you mentioned a few months ago because it threw a code for that and from my understanding they control when the rad fan kicks in & the temp gage inside the cabin. Changing those parts fixed my fan not kicking on & my seemingly glitchy temp gage but the engine was still overheating which is why i gutted the thermostat. So if the connector controls the thermostat heating does that mean it only controls when the thermostat opens and closes? Im still unclear on the function of the connector itself.


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## Blasirl (Mar 31, 2015)

Causes for this engine code, *P00B6*, may include: 

Defective ECT sensor 
Faulty radiator coolant temperature sensor 
Insufficient coolant level 
Shorted or open circuits or connectors 
Bad PCM
PCM programming error
Read more at: P00B6 Radiator Coolant Temperature/Engine Coolant Temperature Correlation

*P0599*

Experience dictates that the problem usually lies in a loose or corroded electrical connector or the electrically operated thermostat itself is at fault. Occasionally, the ECM fails, but is the least likely cause.
A loose or corroded connector on the thermostat 
A coolant leak will cause the code to set 
The thermostat itself has failed 
A short or open has occurred in the wiring harness between the computer and thermostat 
The ECM has failed

Read more at: P0599 Thermostat Heater Control Circuit High Code


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## plano-doug (Jul 1, 2015)

RuinedCruze said:


> So if the connector controls the thermostat heating does that mean it only controls when the thermostat opens and closes? Im still unclear on the function of the connector itself.


I'm not sure exactly when and how the computer uses that heater. But I'm under the impression it does it to open the thermostat at a lower temp than spec - ie, somewhere less than ~221°F. So it does it to open it early, before the coolant has gotten all the way up to temp.
...
My dad had a 1968 Olds with the Rocket 455. It was a finicky beast. I can remember, on cold days, waiting for that thermostat to open so we could get some heat in the car 

Doug

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## plano-doug (Jul 1, 2015)

I wrote:


> I'm not sure exactly when and how the computer uses that heater.


I drilled down on this some more, and got nothing but bureaucratic gibberish.

Here's what Chilton's on-line had to say about the thermostat and its heater:

Engine Coolant Thermostat Heater

The ECM controls the pulse width modulated (PWM) thermostat heater circuit. The engine coolant thermostat heater helps control coolant flow and regulates the engine operating temperature. The ignition relay supplies 12 V to the thermostat through a fuse. The ECM controls the engine coolant thermostat heater by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to a voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.
...
The Thermostat is a regular part of the Thermostat Housing (1). The thermostat controls coolant flowing. It is a grid controlled electronic wax pellet type. By coolant temperature and / or applying current, the wax-pellet of the thermostat is molten what [sic] leads to the opening of the thermostat. That allows the coolant to flow through the radiator. The electronic heating of the thermostat is controlled by the engine control unit. The thermostat begins to open with 0V at 103°C (217°F) and with 12V at 80°C (176°F). It is fully open at 117°C (243°F). Whether the thermostat opening is supported by the electronic heating or not depends on load conditions which are defined as parameters in the grid.​No details there of when or why the computer commands the heating element. My hope was to learn how the heating element enhances the thermostat opening/closing, versus the old way of it being controlled solely by the coolant temp. 

SMH.

Doug

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## plano-doug (Jul 1, 2015)

I whined:


> I drilled down on this some more, and got nothing but bureaucratic gibberish.


Eureka ! 

Ask and ye shall receive 

Digging further - Google is your friend - I found this informative article about "electrically assisted thermostats".

Turns out, a "passenger car engine runs optimally at an operating temperature of approximately 230°F."

New technologies are pushing engine efficiency and combustion quality ever closer to optimum operating conditions. As we push the engine closer to the desired 230° range to improve both emissions and fuel economy, we need a more advanced thermostat technology.

...
An electrically assisted (also called map-controlled) thermostat provides broader and faster operation than traditional thermostats. In addition to the mechanical function of the wax sensing element, electrically assisted thermostats incorporate an electric heater within the sensing element. This heater is controlled by the vehicle’s ECU, which receives information on the speed and load conditions of the engine. It uses this information to regulate the temperature of the coolant. A data set, or map, is stored within the ECU to govern when and how heat is added to ensure optimum engine performance.

Consequently, the thermostat can influence the temperature considerably more quickly, allowing the engine to operate under various load and operating conditions within the corresponding optimum range.

...
When under a sudden, heavy load, an additional heat source comes into play with the map-controlled thermostat. Once the conditions of the stored operating map have been fulfilled, a heating element integrated in the expansion material is enabled by the engine management system. This additional heat source allows the wax to expand quicker, opening the thermostat fully regardless of actual coolant temperature, so the coolant flow is increased, immediately allowing the engine to operate within the optimum temperature range without danger of overheating.

Since the electric thermostat is controlled by the engine computer and mapped to driving conditions, when the sudden heavy demand is removed, the current is shut off to the electric heating unit and the thermostat again acts like the traditional wax unit with a fully open temperature of approximately 230°F. ​
What I especially like about this system is that it fails gracefully. Even without the heating element, the thermostat still opens and closes to protect the engine, albeit less efficiently, but your motor won't melt down without it.

HTH.

Doug

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## RuinedCruze (Mar 30, 2020)

Wow ! Honestly i think that answers all my questions, thanks. ? now just to find the right part & install it? ill post an update with pics & my experience after i fix er up!


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## -loki- (Dec 13, 2019)

For the cost effective I say go to the bone yard and cut the plugs with as much wire as you can. Make a linemans joint, solder and heat shrink.








You'll never have to worry about that joint.


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