Temp gauge close to 'C'

1996 buick century, 3.1L, 123,000 miles on odometer.

I purchased this vehicle from an Aunt in WV. Drove it 280 miles to my home in TN. The temp gauge rarely if ever went above the 1/8 mark on the C-to-H temp guage. This particular instrument cluster only has the C-to-H markings. When I pulled particularly long WV hills at low speeds, the temp would move to 1/4 mark, but as speed was achieved on downhill, it went back to 1/8 mark. Even at 65 and 70 mph on interstate, on level and hills through VA and TN, the temp never climbed to 1/4 or 1/2. I got into my city, expected the temp to climb when I slowed down on city streets. Temp still only showed between 1/8 and 1/4 for about 5 miles, then back to hover at 1/8 mark. Is this a thermostat that is stuck open and not working properly?

Could be the thermostat stuck open. Also, possible ECT sensor not giving the right signal to the PCM/ECU module and then the IP temp. gauge.

With the climate control in heat mode how does the air feel. Cold, warm or hot?

The easiest way to figure these out is with a scan tool. While monitoring engine data you can compare the the reading from the temp sensor to what the dash is reading. If the coolant temp on the scan tool also reads cold than there is a strong likely hood that the t-stat is stuck open. After the car sits over night start it up and then monitor the temp of the upper and lower hoses with your hand (safely!). If you feel them warming up soon after you start the engine than likley the t-stat is open.

Could be the thermostat stuck open. Also, possible ECT sensor not giving the right signal to the PCM/ECU module and then the IP temp. gauge.

With the climate control in heat mode how does the air feel. Cold, warm or hot?

Thank you for the response to my question. I don't recognize the acronyms here. What are ECT, PCM, and ECU? Would you be kind enough to elaborate what they stand for and the function of those?

The easiest way to figure these out is with a scan tool. While monitoring engine data you can compare the the reading from the temp sensor to what the dash is reading. If the coolant temp on the scan tool also reads cold than there is a strong likely hood that the t-stat is stuck open. After the car sits over night start it up and then monitor the temp of the upper and lower hoses with your hand (safely!). If you feel them warming up soon after you start the engine than likley the t-stat is open.

Could this be done using the basic scan tool that would be loaned from Advance Auto Parts or Auto Zone?

ECT = Engine Coolant Temperature Sensor
PCM = Powertrain Control Module

To check engine temperature you will need a full function type odb-ii scan tool. From what I recall the ones at Autozone or Advance are basically codes readers which will read out generic or extended diagnostic trouble codes (DTC), freeze frame data, history codes and emissions readiness status. But it doesn't hurt to ask them. Autozone's policy at least in my area is no scan unless there is a check engine light on.

If you are not DIY capable or without the proper diagnostics equipment then you might consider taking it to an independent auto repair shop or the GM dealer. The auto parts stores are in the business of selling parts and not too good of a reliable tech source or if you really want to get it fixed although they do scans for free.

I'd would have to agree. They are a great resource for finding out what the codes are but that is all they should be used for. There are some people that work there who have a great knowledge of cars but there are many more that don't. They are in the business of selling parts. Leave the diagnostic/repair to the guys who do diagnostics and repair!!

ECT = Engine Coolant Temperature Sensor
PCM = Powertrain Control Module

To check engine temperature you will need a full function type odb-ii scan tool. From what I recall the ones at Autozone or Advance are basically codes readers which will read out generic or extended diagnostic trouble codes (DTC), freeze frame data, history codes and emissions readiness status. But it doesn't hurt to ask them. Autozone's policy at least in my area is no scan unless there is a check engine light on.

If you are not DIY capable or without the proper diagnostics equipment then you might consider taking it to an independent auto repair shop or the GM dealer. The auto parts stores are in the business of selling parts and not too good of a reliable tech source or if you really want to get it fixed although they do scans for free.

OK, thank you for explaining those. Those have meaning to me. I am DIY-capable and have changed out thermostats before. I'm betting I can do a Coolant Temp Sensor test using a multi-tester without taking the sensor out, right? Are there any on-line sources that could be used for determining tolerances/readings for such a test? That sensor is down in the lower radiator, right? Powertrain Control Module is also known as the 'computer,' correct? I have access to a digital multi-tester.

Being DIY capable is a good start. The thermostat on the VIN "M" 3100 V6 engine can be a bear to replace but definitely can be done with patience and the right tools. The ECT/CTS is just a thermistor so you can check the resistance/calibration of it with a digital multimeter (DMM). All you need to do is remove the electrical connector to it to test the sensor without removing it. There should be an input which is the PCM 5 volt reference signal and the output which goes to the PCM module and maybe a ground wire. Just go across the contacts at the sensor. Wiring color coding varies. See chart below for resistance values and corresponding temperature. The sensor should be located at the driver's side of the upper part of the engine around the thermostat area. Either in the cylinder head or lower intake manifold.

http://i5.photobucket.com/albums/y186/lizzywiz/ect.jpg

Coolant temp sensor will be in the lower intake minifold. If you standing on the drivers side of the car it will be on the right side of the t-stat. It will not be easy to get at!!

I have the same problem with my 1999 LeSabre. The coolant temp is always low and the Amp meter is always way too high.
I changed out the thermostat with no change to the gauge readings.

I recently got a Scangauge II and it confirmed my collant temp at 195* and my amps at 13.4 or so. I bought the Scangauge to get better mileage but this extra gauge feature and code reading capability is nice and it works on all OBDI II vehicles 1995+

Did some repairs yesterday, thought I'd post some results, since ya'll gave advice.
While idling with hood up, found water/antifreeze being 'flung' off the pulley and belt onto back of radiator. Hadn't seen this originally, but figured bad waterpump gasket or bad water pump. Went under car to drain down the radiator, but with the drain-valve open as far as I could get it, NO LIQUID CAME OUT! :confused: I figured I'd've had a steady stream. I began closing he valve and got only a few drops to come out. I opened it and closed it and same thing, but no 'stream' like I'd expected. :confused: My driveway is a 30-degree incline, so I figured gravity would be my friend in that case. I closed it up completely and began pump replacement. Removed lower water pump assembly hose and had a HUGE GUSH of water/antifreeze come out. So much for my thinking that the system was empty. When purchasing the pump, I didn't purchase Dex-Cool or other product: I figure to get a flush done and replacment done when vehicle is put on road permanently. It isn't currently our daily driver until my other sedan is sold. SO...I put in water only, diluting the Dex-Cool still in the system. Running constantly for 10 minutes, bleeding from BOTH bleeder valves, and watching the radiator overflow 'burp' frequently, the temp guage moved to the 1/4 mark, which is where I figured that it should be under normal use. I'm digging into the temp sensor over the course of the next week with a multitester. Thanks for leads and I'll post updates of the progress.

What is the 'normal' temperature reading for the Century's 3.1 engine under normal use? Does it fluctuate between 1/4 and 1/2 mark, or lower? There's no notation in the owner's manual as to what to expect.