Does the '94 850 have one of those odd 'middle of the dial' tpe temp gauges, like some of the 240s?
My radiator cap cracked yesterday, and was spewing coolant for who knows how long, until the low water light came on...the gauge never moved from the middle. I also have noted on a hot day, with A/C on and pulling a grade, it does not move, and in the winter moves to the center fairly quickly.
If it does have that weird circuitry, what is the fix to have some idea what the engine temp really is?
Yes, it's like that, but if it doesn't show overheating, (assuming it's working as designed) then is really isn't. It's only to hide normal running fluctuations from you so you don't go running to the dealer every time you gauge goes up a millimetre higher than normal. Normally your car's cooling system has enough reserve capacity that it won't overheat in this situation.
might as well have an idiot light, then... If you don't know that the fluctuations are normal, you shouldn't have a gauge nor a Volvo..maybe a Chevy or something mindless like that...
It's not a direct gauge. The temp sensor is connected to the combined instrument module, whose microprocessor moves the stepper motor pointer.
There's a test mode (in the 94's) to see of the pointers and odometer are working. There's also a fault code readout to see if the sensor is working.
Find the underhood test connectors and plug the wire into hole A7. Turn the ignition on.
Fault codes:
Press the button once, briefly (About 1/4 second)
Watch the LED and count the groups of blinks. such as 1-2-2. When it stops, press the button again, keep doing this until the first code repeats.
The two temperature sensor faults are: 1-2-1 and 1-2-2.
Function test:
Turn ignition off and on again to reset test mode 1, and then press the button 3 times.
Look at the instrument panel for the following indications: Fuel gauge: Half full. Speedometer: Vertical. Tach: Vertical. Temp: Edge of the red mark. Odometer: Advances 5 tenths.
If the temp pointer remains at midpoint, then it's the instrument pod ($$$$)
If you had a new Volvo, the status would be impossible to obtain without a $50.00 visit to the dealer. This is why I'm not considering a new VOlvo to replace my 94.
BTW: The temp sensor is also used by the engine management computer, and it it wasn't working, you'd probably have a check engine condition by this time. .
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