Fan kicking in almost immediately after start-up and strange

[dc_saab]

Hello out there.. in SAAB World.. for some reason my 97 900SE turbo kicks the fan on almost within 20 seconds of startup.

Anyone experiencing this as a norm? I thought the fan only kicked on when the temp. Also noticed my SID displaying weird temperature readings and after driving for a while the temps get to norm. anywhere from 90 to 125F.. and cold air running from my system for heat settings of 72+ degrees F.

Thoughts anyone.. I'm guessing its time for a good flush and change of my coolant fluid, thermostat and water coolant sensor. Every so often on stops the SID will pop on water coolant level low even though I have a full bottle.

I figured it was time to replace the water pump, belt, coolant sensor, and thermostat to get ahead of any related issues.. but still trying to figure out what's causing the fan to kick on.. Does the outside temp sensor tell the system when to kick on the fan and whether to provide heat inside the car on climate control?

something about talking it out here makes me feel like I've answered my own question somewhere in those details..

guilty of using Prestone when I changed my coolant fluid... hmmm.. that must be it huh.. ??

[MI-Roger]

I have read that this problem is caused by a faulty fan speed controller/resistor unit on the NG900 vehicles. On-line prices are $27 for this resistor. The same posting said that the back side of the fan speed resistor is a metal plate which is to be placed against a metal frame beneath the dash to absorb the waste heat. Use of a vial of thermal paste from a computer store may be a wise addition to improve heat rejection from this resistor.

[dc_saab]

MI-Roger.. thanks for the response.. that makes sense. thank you

[Dave 2 93s]

I'm confused.
When you say the fan kicks in almost straight away, you mean the radiator fan?
The SID temperature reading is random until the car is warm.
And when your car has been driven a while and the engine temperature gauge(below the turbo gauge to the left , opposite the fuel gauge) is reading around the half way point. The SID display settles down.
And your ACC temp is set at 72+F, your getting cool air from the air vents.
My thoughts are.
SID temperature reading is the outside temperature, and the sensor is located in the middle of the front bumper at the top of the bottom grille. If the sensor is loose and hanging down, it might be picking up the temp of the oil cooler or intercooler.
When the engine temp gauge is reading in the norm and cool air is coming from the ACC, this could or would be an indication of low coolant level. But as you have coolant in your expansion bottle is could be an air lock in the system. Usually the internal heater matrix is situated in the system that it would be the first thing to be starved of coolant if the system was low or leaking. Because the loss of it first would have no effect on the engine.
The radiator fan is controlled by ... Big breath. the Dashboard Integrated Central Electronics Control Module. DICE for short.
and it takes information from the coolant temperature sensor, the air conditioning pressure, the vehicle speed and the out side temperature.
So initially I would be looking towards the temp sensor in the front bumper being in the correct place, and an airlock in your internal heater system. this could be done when engine is cold, by opening up one of the two heater pipes (preferably the return one from the heater) The two black hoses from the engine , to the centre of the bulk head area. Air could escape out and water should then appear instead and then top up the expansion tank. They are both quick and simple checks that should only take you less time it took me to type it.
Hope it is of use
Cheers for now
Dave

[dc_saab]

That was indeed the case.. While changing out my intercooler.. had to remove the grill and bumper and didn't realize in doing so I had inadvertently removed the outside temp sensor.. and simply left it hanging in the engine bay near the left headlight. In fact.. I wasn't even sure what it was when I saw the long twisted wire running from it.. As sophisticated as this car is.. wasn't expecting that.

Reattached to the bumper area and no more hearing the fan come on too soon.. and my SID temp is reading at normal levels again

thank you

[Dave 2 93s]

Brilliant. It's always good to hear a happy ending. And good to hear the cure you found, was in the area that my fuzzy logic lead me to too.
Cheers for now
Dave