Temperature gauge not working A/C blowing hot

Hello,

If the temperature sensor is not working or the computer is having an issue the A/C will not engine because the PCM thinks the engine is overheating. A new temperature sensor can help, but lets start by running the codes to see what comes up. here is a guide to help us get started, the temperature sensor location is in the diagrams below.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Check out the diagrams (below). Please let us know what happens.

Get a scan done to find out what is causing the check engine light to come on. A scan tool would allow you to see the engine temperature, unless if the temperature sensor is bad.

Once engine has been started for a minute or two, it would be okay to drive around even if you feel the engine might be running cold. Overheating on the other-hand would be a cause for concern.

Did you happen to get the trouble code numbers or just clear them?

Well it is kind of hard to armchair it then, but I would say if it went away with simply clearing the codes that it is probably going to be an intermittent problem. Possibly in the wiring to the coolant temperature sensor. If it happens again, get the trouble code number(s) and we will go from there.

With your description I would suspect that the harness or connector at the sensor is the issue as it failed not long after the connector was moved. The fans should not run all the time. They are controlled by the engines temperature and AC use. Not a fan of any sealers as they tend to seal more than just the leak they were intended for.
I would remove the connector and check for loose or corroded pins. Also check the harness itself for damage, it does not take much to rub or melt through the wiring. If you have access to a good scan tool that has bi-directional controls many can do a gauge sweep that would show if the gauge itself was okay.

From your description it sounds like the connector. Use your meter and with the connector unplugged the tan wire should be a ground and the yellow wire should have 5 volts on it. The resistor in the ECT changes the 5 volt signal based on temperature and the PCM reads that and determines engine temperature. It then sends a signal through the data bus to the dash telling it to display the temperature. The gauge is a stepper motor that simply moves to the proper point. Those are a common failure item in the older vehicles but the gauge sweep test should show if it works. Many newer cars usually also sweep the gauges at initial key on. If yours moves the gas, speedometer, tachometer, oil, temperature (what ever it has for gauges) when you turn on the key and the others move but the temperature does not then it could be a faulty stepper motor.

I would say to measure the resistance of the thermistor in the sensor but they rarely fail, it is usually the connector or the harness. Please post back with what you find.

What usually happens is the connector gets corroded or the harness starts to fail. Then, "I will replace the sensor". In the process of removing and replacing the sensor the harness gets moved around and the connector is removed and put on the new part and "miracles abound" the widget starts working again. Had to be a bad part. But it was actually the act of moving the wiring that repaired it. That is why most good diagnostics folks start testing without actually touching the component until they are 99% sure that it is in that area. Nothing like trying to write up a repair when you do not know what it was you moved or disconnected that suddenly brought it back. Plus you cannot say "I know it is repaired and will no't cause that problem again".

Hi,

I doubt the two are related. However, is the engine coolant full? Is the heater working?

If the coolant is full and the heater is working, then we have flow. So, the next thing would be the engine coolant temperature sensor (ECT). Here is a link that shows how in general how one is replaced:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

Here are the directions specific to your vehicle. The attached pics correlate with the directions.

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2006 Pontiac G6 V6-3.9L VIN 1
Removal and Replacement
Vehicle Powertrain Management Sensors and Switches - Powertrain Management Sensors and Switches - Computers and Control Systems Coolant Temperature Sensor/Switch (For Computer) Service and Repair Removal and Replacement
REMOVAL AND REPLACEMENT
ENGINE COOLANT TEMPERATURE (ECT) SENSOR REPLACEMENT

REMOVAL PROCEDURE

NOTE: Use care when handling the coolant sensor. Damage to the coolant sensor will affect the operation of the fuel control system.

pic 1

1. Drain the cooling system. Refer to Draining and Filling Cooling System. See: Cooling System > Removal and Replacement
2. Remove the intake manifold cover, if necessary.
3. Disconnect the engine coolant temperature (ECT) sensor electrical connector.
4. Remove the ECT sensor.

INSTALLATION PROCEDURE

NOTE: Replacement components must be the correct part number for the application. Components requiring the use of the thread locking compound, lubricants, corrosion inhibitors, or sealants are identified in the service procedure. Some replacement components may come with these coatings already applied. Do not use these coatings on components unless specified. These coatings can affect the final torque, which may affect the operation of the component. Use the correct torque specification when installing components in order to avoid damage.

pic 2

1. Coat the threads of the ECT sensor with sealer GM P/N 13246004 (Canadian P/N 10953480) or equivalent.
2. Install the ECT sensor.

NOTE: Refer to Fastener Notice.

Tighten the ECT sensor to 20 N.m (15 lb ft).

3. Connect the ECT electrical connector.
4. Install the intake manifold cover, if necessary.
5. Fill the cooling system. Refer to Draining and Filling Cooling System. See: Cooling System > Removal and Replacement

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Let me know if that helps.

Joe