I was having starting trouble when the weather in the northeast began to get bitter cold. I replaced the battery. After which the fan in the engine compartment runs on after turning of the engine, for about 10 minutes. Now starting is getting troublesome again on cold mornings (<20 degrees overnight)

Any thoughts why the fan is running after shutoff in below freezing temps

Gregg

Here's an FYI to everyone who has had this problem. I have read countless posts and followed much useful advice. I changed the temp sensor, the fan control relay, the maf sensor and the fan ran continuously. I finally found that none of these parts had been bad. When changing the temp sensor, I failed to notice the tremendous amount of corrosion inside the positive terminal of the sensor connector. Cleaned this, put dielectric grease on it and it sured the hard starting, the fan running and the lack of boost from the turbo. $250 in un-needed parts and several hour in wasted labor all because of corrosion in a connector. Always check the simple things first! Apparently a bad signal from the temp sensor causes multiple problems such as hard starting, fan override that forces the fan to stay on in 'safety mode' and it also tells the ecm to kill the turbo boost. Hope this helps.

I was having a similar problem, though my engine was barely warming up(according to the temp gauge), and fan would run for a while after shutoff. Turned out to be a worn out thermostat, changed that, and the problem ceased.

Here's an FYI to everyone who has had this problem. I have read countless posts and followed much useful advice. I changed the temp sensor, the fan control relay, the maf sensor and the fan ran continuously. I finally found that none of these parts had been bad. When changing the temp sensor, I failed to notice the tremendous amount of corrosion inside the positive terminal of the sensor connector. Cleaned this, put dielectric grease on it and it sured the hard starting, the fan running and the lack of boost from the turbo. $250 in un-needed parts and several hour in wasted labor all because of corrosion in a connector. Always check the simple things first! Apparently a bad signal from the temp sensor causes multiple problems such as hard starting, fan override that forces the fan to stay on in 'safety mode' and it also tells the ecm to kill the turbo boost. Hope this helps.

Maybe the fan did that before you changed the battery, and that is what killed your battery.
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'96 855R,'64 PV544 driver, '67 P1800 basket case, '95 855, '95 854, the first three are mine, heh, heh, 415,000 miles put on 9 bricks

OK . But why does it run after engine shutdown?

This morning was 9 degrees, and rough start....Could it be semi-fouled plugs?
Gregg

The rough start could be an indication that you are in need of an oil change. If you are not running 5W30 at 9F, it will take a while for the hydraulic lifters to get pumped up with oil.
As for the fan running, what does your temp gauge look like on the dash? Does the fan start up when you start the car? If so, then it could be just a fan relay, under the fan shroud.

Klaus
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1975 164 w/174,800mi (Sold) 1995 850T w/91,000mi, 1998 V70R w/129,000mi

Ona friend's 98 V70 XC it was the coolant temperature sensor, but in that case the temp gauge was pegged to red and the car wouldn't start, also, no codes were stored. You would turn the key to on and the fan kicked in right away.
Unplug it (next to the thermostat housing) and see what happens. It's a $50 part, but easy to fix (if that's your problem).
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1966 122S Wagon- so far, 1800ES Rear Axle and Front Discs, Overload Springs, Wilwood Double Res MC, upcoming-rebuilt engine, DCOE's or Mikunis, electric fan