Radiator Cooling, Fan Not On If Car Off

[Mguyross]

Radiator cooling fan not on when ignition off, does (both) run if ignition turned back on or when engine is running. Engine runs at normal temp even in hot weather. However, when standing with ignition off, reservoir over flows, and often requires refilling upon returning to car after it has been off over night etc.
I am assuming this is due to some sensor or relay that controls fans when engine is off, but without shop manual I have no idea what or where.

[9-3 Aero]

The reply given is pertaining to a MY2004, as the MY in question is not known (or engine, for that matter).

It's common sensors, relays and control module (DICE) controlling fans when engine is on and off, however are the fans always running at low speed when ignition is in "OFF" position. When to start is given by two modes, one of which is operating the fans when the fans does not turn when the ignition was turned from "ON" to "OFF", and the other mode if the fans were turning when -.

The modes operates the fans in a (timewise) pattern, given by different temperatures below 103°C, between 103- and 107°C and above 107°C. The main instrument temperatur gauge moves out of the 9 o'clock position at 115°C for a 4 cylinder petrol.

The fans are controlled by three relays, one for low speed and one each for right - left fan, high speed. The relays are all the same kind. In case you are not sure whether or not the fans are running low speed (when engine is on or off), you could swap low speed, FR8 in the engine bay relay box with either FR9 (right hand, high speed) or FR11 (left -), as a troubleshooting step.

Note as well that there are many reports with regard to a failing expansion tank cap.

[Mguyross]

My Saab 9-5 SE is a 2001 6cyl turbo. As to the relays: with ignition on both fans are running, so I switched out a High I with a Low, and the fan still does not come on with ignition off. I am therefore concluding that it is not the relays. The over flow is through the cap (therefore making me believe there is not a leak elsewhere in the cooling system), but only when the car is sitting after it has been running a while and then turned off and sitting for enough time for the pressure to build. The fan does not come on after running and then ignition is turned off.
Thanks

[9-3 Aero]

To be verified:

The radiator fan low speed is activated as follows, from “cold engine”:
Starting when the coolant temperature reaches 97°C and stopped when the temperature drops to 93°C.

Radiator fan does not run when ignition is turned from ON to OFF:
30 seconds after ignition OFF:
- The radiator fan starts and runs for 3 minutes if the coolant temperature is 107°C or above. After 3 minutes the fan stops.

The radiator fan runs at low speed when ignition is turned from ON to OFF:
- The radiator fan continues to run for 30 seconds if the coolant temperature is 103°C or above.
- The radiator fan stops if the coolant temperature is below 103°C.

And you are sure that the cap is now not opening at a lower pressure than specified?

[Mguyross]

I am ordering a new cap, just to be sure. How ever, in the 10 months I have owned this car, I have become used to hearing the fan come on most of the time when I shut off the engine. Now I do not hear it at all after I shut off the engine. Today, I let the engine idle until the temp had been a normal running temp (on the temp gauge) for a period of time. When I turned the engine off, the fans did not come on. When I turned the ignition on (with out running the engine) the hi fans came on. When I then turned the ignition off no fan came on. When I drive the car next, I will pay attention to the fans after I turn off the engine, with consideration to the time sequence you gave me.
It is summer here (Western Slope of Colorado) with temps in the 80's f and sometimes higher. Often when I have the reservoir loose coolant I have driven 35+miles in mid 80's - to mid 90's and then stopped and it is under those conditions that the reservoir is likely to overflow during the down time.
Thanks

[9-3 Aero]

Now knowing the MY and engine, the fan relays in question are F7 (low speed when engine is on or off), FR8 (left hand, high speed) or FR12 (right -). I assume the swap tried was in accordance with this.

As I don't see you've noticed the fans running slow speed, engine on, the "slow speed" relay is still a suspect, or even more the "slow speed" fuse #15 in the engine bay fuse box.

Have you started the engine, let it idle from "cold" and been listening when the fans started - which should be in slow speed? This should happen at 97°C -, and high speed kicking in not until 107°C coolant temperature.

[Mguyross]

Since the relay now in the Hi fan position was the relay from the Low fan position and both Hi fans are running, I am assuming that the relay is good. I have, at various times, checked and/or exchanged the fuses, I am assuming that they are good. I have not yet, but will, today, do the observation of the fan sequences that you sent me earlier. I have printed that sequence and will do it and let you know the outcome. Thanks again

[Mguyross]

As I indicated that I would, I observed my car noting the fan sequences that you had provided, and when I am patient enough both fans do come on, as you described. This morning I drove up a 2,000ft elevation/5miles at about 80'f. And although the fans came on after the ignition was off, the reservoir did overflow through the cap. I did order a cap this week end and it shipped from California today (I'm in Colorado) and with luck it will be here mid week. I will let you know the outcome with the new cap.
Thanks again.

[Mguyross]

Done. The new cap has been in place for a few days and I have repeated the actual driving conditions that caused the overflow, with no overflow. Thank you. Back in the days of fan belt driven fans and flip lever pressure release caps that would have been my first guess. I guess I just over though it. Thanks again.

[9-3 Aero]