Is the engine thermostat dash gauge and air conditioning connected

Tiny
MICHELLEFWBFL
  • MEMBER
  • 2008 ISUZU ASCENDER
  • V6
  • 4WD
  • AUTOMATIC
  • 190,000 MILES
Sometimes my cars dash gauge for the engine temperature doesn't "work" and until it does the A/C will not blow cold air. Sometimes it will go back to working after driving a few minutes. Sometimes I could drive around for an hour or so and it not work, but mostly it will work after turning the car off then back on. Sometime that will fix it right away other times it may not. For several tries. What is causing this? It has only happened a couple times in the summer but the past few days of cooler weather it has happened several times. Kinda annoying because I know my A/C works great. It has something to do with that temperature gauge. Which has nothing to do with the A/C working. Any help please?
Wednesday, October 23rd, 2019 AT 3:01 PM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Welcome to 2CarPros.

Believe it or not, the two can be connected. If the computer loses signal from the engine coolant temperature sensor, it will turn off the AC because it doesn't know if the engine is okay or overheating. If overheating, it removed the load of the compressor from the engine.

With that, first check the connection on the sensor. If everything is clean and tight and not corroded or damaged, chances are the sensor is bad or the wiring under the insulation has been somehow affected. I would at that point replace the sensor.

Please keep in mind there are other things that can cause the sensor issues such as the power-train control module, but the sensor is the cheapest and easiest thing to replace.

I attached a picture of the sensor and location below. I circled both the sensor (left side) and connector (right side).

Let me know if this helps.

Take care,
Joe
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Thursday, October 24th, 2019 AT 7:23 PM
Tiny
MICHELLEFWBFL
  • MEMBER
  • 4 POSTS
Is there a code that I will get if it's bad? I'm not a mechanic so is this something I will need to take in? And is that diagram under the dash do I need to take off something to find it? Thanks so much for the point in the right direction.
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Thursday, October 24th, 2019 AT 8:20 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Welcome back:

The picture I attached is the engine. The sensor screws into the side of it. As far as a code, it could be one of a few different ones. P0116, P0117, P0128 and so on. The 128 indicates the sensor is showing an overheat.

Let me know if I can help.

Take care, '
Joe
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Thursday, October 24th, 2019 AT 9:00 PM
Tiny
MICHELLEFWBFL
  • MEMBER
  • 4 POSTS
Thanks I will check those in the morning!
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Thursday, October 24th, 2019 AT 9:06 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Welcome back:

Let me know what you find.

Joe
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Friday, October 25th, 2019 AT 4:14 PM
Tiny
MICHELLEFWBFL
  • MEMBER
  • 4 POSTS
Hi, I had the engine light code checked and it came back with P0128 coolant thermostat and P0418 secondary air injection system relay A control circuit. Do you think I should replace thermostat and have my system flushed/filled at same time? Or just do the coolant temperature sensor? What about the other code? By the way, that one was listed twice. Would they be related?
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Monday, October 28th, 2019 AT 7:56 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,114 POSTS
Welcome back:

That code indicates the thermostat isn't allowing the engine to warm up properly in a given amount of time. Because that code is specific to a failing thermostat, that is where I would start. Here is a link that shows how to replace a thermostat in general:

https://www.2carpros.com/articles/replace-thermostat

Here is a link that shows how to flush the cooling system:

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars

The P0418 is related to something different. That isn't going to cause the temperature issue. The code deals with secondary injection control circuit. That is an emissions related issue.

Let me know if this helps.

Take care,
Joe
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Monday, October 28th, 2019 AT 9:21 PM

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