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Discussion Starter · #1 ·
Hi.

When I am talking about engine temp, I am watching the Teng in OpenSID.

Can anyone please help me with a problem where ACC fan makes the engine cold?

SAAB 9-5 2.0t MY2007

So, it started yesterday, when I was driving my daughter to kindergarden. It was -4C outside. As usual, I would heat the engine till about 35C so it is somewhat warmer in cabin. Every morning, while I am taking the daughter into kindergarden, I leave the engine running. When I come back, engine would be at about 80C. But this time the engine would be around 55C (25mins after startup). I drove for 20min more, but the engine temp did not get past 55. The ACC would be set at 1/2 speed at 22C. But it was blowing just a bit warm, not enough.

So, I ordered a new thermostat and a new coolant temperature sensor.

Changed them the same day, and engine did not get past 65C (but it was now -11C by the evening). Again, the ACC fan was set at 1/2 speed and 22C. So, I thought the new thermostat would be defective.

The next day (today), to confirm it, I took out a thermostat from my parts SAAB 9-5 (sitting still for about 6months), which was changed in 2019 and newer had any problems.

As today the outside temperature was 0C-1C, the engine got warm till 73C.

At this point I am sure it is not the thermostat and started to look for a patterns.

(These are with ACC fan set 1/2 and 22C)
1.When the car is idling, the temps would climb. Slowly, but reach about 84C.
2. When I start driving even as slow as 10-20km/h, the engine temps would start to drop till 73C and even lower.
3. The radiator fans are not engaging at this point.

And then I switched off the ACC fan off.

4. Now the temperature starts to climb as it should (fast).
5. It reached 99C and the fan kicked in (low speed) and dropped to ~90C. And this was going on in circle.
6. With ACC fan off, I was driving around at 60km/h, the temp did not drop below 90C.
7. As soon as I turned ACC fan back, the temps started to drop to low 70C`s.
8. I removed fan relays (8 & 9) from engine bay, thinking that by some error fault the radiator fans would turn on while driving, but that changed nothing.

So, now I am at loss. How can it be, that the ACC fan is making the engine cold?
Any ideas?

Thank you.
 

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Discussion Starter · #3 ·
As I stated, I installed brand new as well as a known good one.
Once I switch the ACC fan off, the temps are good and stay at 90C no matter the speed.
 

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What your ambient temperature sensor reads ambient temp?
 

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Discussion Starter · #5 ·
Do you mean the temperature in the cabin or outside?

Outside was about -4C.
Inside - don`t know. But it is not as hot as it was.
 

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Outside.
Do you have similar issues if you run ACC full AUTO (do not make any changes at all)?
Do you have anything on dash (hats, gloves etc)?
 

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2005 9-5 Aero Wagon
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I don’t know if engine temperatures during the winter being low is cause for concern… I was just in BFE Norway with -10° C OAT and the engine of my rental car never even got above a quarter warm when I ran the heater - which was necessary for survival.
 

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-10 is balmy...-27 here tonight.

No matter how cold it gets here my car shows regular temperature, nine clock on the gauge.
 

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The heater core does act as a mini radiator but the thermostat should compensate in a matter of minutes for any substantial draw of heat away from the engine. What does the temperature gauge in the instrument cluster do? You will get a check engine light to come on if the engine fails to maintain adequate running temperature. I’m guessing you have air in the system which is messing with the temperature sensor. You may need to burp the rest of the air out. One other thing- the weep hole in the thermostat needs to be oriented correctly. Did you do that?
 

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Discussion Starter · #12 ·

So, I made a video, to show how the problem is occurring.

At the start of the video, the ACC fan is off. As you can see, while driving around 10-60km/h, the engine is rising from 80C to 87C.
Then @4:50 I turn the fan on to about 55%, and the engine temp starts to decrease to 74C.
@10:35 I turn the fan on 100% and then it got down to 68C. It would go lower, but I got tired of holding the phone.

What else have I noticed - when the engine is cold and I have fans on 100%, the engine would get only to 55C-59C and not higher.

I’m guessing you have air in the system which is messing with the temperature sensor. You may need to burp the rest of the air out. One other thing- the weep hole in the thermostat needs to be oriented correctly. Did you do that?
I don`t think the air in the system would give these symptoms. It would not matter if fan is on or off, won`t it?
As of the bleeder hole - yes, it is oriented correctly on top.
 

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Discussion Starter · #14 ·
Yes, as engine cooling temp drops, the air coming from vents get colder as well.
 

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I think you have an air lock in the cooling system.

Does the temperature change more quickly under harder acceleration?

Does the coolant level change when the car is revved a little?

Do you have a coolant bypass valve installed?

Are you losing any coolant?
 

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Discussion Starter · #16 ·
Under acceleration the temperature rises slightly. About 5C-8C more.

About level rising on revs - will have to check that.

If MY2007 has the bypass valve at the same location as MY98, then no, there is no bypass valve.

Ever since I got LPG installed on September, I have to top up the coolant level about once in a month. But it is about 100-200ml.
 

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Replace thermostat to original.
 

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A few points:

  1. Saab 9-5 heater is strong enough that it will drop the engine temp when it starts running at higher fan speeds to warm up the cabin when first running in cold weather
  2. Old ACC up to '05 model automatically adjusts fan speed and distribution based on engine temp. If the later style does as well, I recommend leaving it on AUTO to do its thing. (Fan starts very low speed and defrost, then as engine warms up the fan speed increases, and adds floor distribution at around 50º C engine temp.)
  3. Check the temperature of the radiator hose. It should stay completely cold for a long time. If it is at all warm, and the engine has not warmed up to complete operating temperature, then there is an issue with the thermostat (or possibly something else).
  4. "Known good" thermostat is an unknown quantity. I (and others) have found that Saab OEM thermostats in a Saab box work best. Get one from Mimmi. "Equivalent" thermostats, even from quality suppliers like Motorad, don't work as well. And that is even when the thermostat in the box is marked "Motorad" as well. (They were not identical!)
 
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