Temp problems

I have a 1997 Grand AM with the 3.1L V6. The problems I am having is that the temperature gaugu fluctuates when I am driving. I know it is normal to fluctuaute somewhat but it is just fluctuating too far. It will run with the needle around 1/4 up and in a second iit can be 3/4 of the way up and go down just as fast. I was thinking the thermostat but I just replace it. Any suggestions??

Since your car probably doesn't change temp that fast(especially down), I would suspect a faulty temp sender. When they start to fail, they give readings similar to this.

One way to test would be using an infrared temp reader to test the temperature of the t-stat housing.

Most likely, as tight suggested, it sensor-read problem.

If got a multi-meter handy, ya can test the sensor

Process is~~~~~~~~~~~`

Ohm the sensor at cold engine, harness unplugged,

Cold means ambient temperature in the air, not the engine


examples in F degree

ambient temp. 30-40 degrees above frezze F.
Range should be be around 2238-1459 ohms, going from 2238 at 30 deg. to 1459 at 40. If ya have a specific ambient temp. you plan to test, I can give an ohm-read spec, but generally as ambient temp. ups, the ohms should drop.

Also, but BE CAREFUL of your probes, you can probe the harness itself, two wire plug, but MAKE SURE your multi is one that is auto-reverse polarity type, so ya don't short it, it simple power-ground two wire, but I no clue which is which.

Anyway, Volt check the harness plug, engine on but not running, You should see around 5V at the harness. {reference Voltage signal}


Or backprobe the harness, engine running,
generally the V read should be high when engine cold, and drop as engine warms.

But, only do this if you confident of trying this, or your meter is AUTO-CORRECT for reverse polarity, K?

Hope this helps