palmettonative

This is my first summer with my 1995 993. It's been really hot (96F with high humidity and heat index around 110F). After driving today for 30-40 minutes, went into the store and came back to find some sort of fan or blower was running. It was 15 or 20 min after the car was not running.

Is this normal? Also when I got home, I turned the ignition off. No fan was blowing...went into garage 5 min later and it was blowing again....

Any help?

Scott

Reddy Kilowatt

Normal IME.

palmettonative

does it mainly do that when really hot outside? i went back to garage after 15 more min and it was stopped. I've had the 911 about 10 months, but the heat lately has been very bad as of late.

95C4VanIsle

Yes, it is normal for the fan to continue to operate for up to twenty minutes if the engine is hot. It shuts down automatically after twenty minutes.

Falcondrivr

It's your rear blower motor. It cools down the exhaust system in hot weather. Normal.

IXLR8

What I'd like to know is under what conditions does the rear blower motor turn on and under what conditions does the rear blower motor turn off. Is there a logic diagram anywhere on this?

I know mine was working, but with the cooler temperatures, I haven't heard it come on in a while.

The rear blower motor shows continuity.

Looking at the electrical diagram, it seems to be controlled by a blower relay which is in turn controlled by the CCU.

95C4VanIsle

I don't know about the electronics but according to Adrian Streather's book:

With the ignition off (engine not running) the additional engine cooling system remains armed for 20 minutes after the engine has been turned off. If the detected outlet pipe temperature is less than 104 degrees F the system will not activate the blower and is not armed. If the temperature is between 104 and 167 the system remains armed. If the temperature rises above 167 the rear blower fan will be switched on to the low speed setting only until the outlet pipe temperature reaches 158 F, when it will be switched off.

Low speed rear blower fan operation is at apprximately 9 volts to decrease the possibility of draining the battery.

Adrian's book has more information on the different modes of operation (pg 349) if you have the book.

Hope this helps.

IXLR8

Damn, I do.

And here I was in the OEM Porsche repair manuals going through the electrical schematics last night.

Thanks!!!