986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - How long should Fan run for after car is switched off.

MNBoxster · 11-11-2006, 11:47 AM

Hi,

The Engine Compartment Purge Fan (Porsche Parlance) certainly can come ON/OFF multiple times, but should it? The Fan is supposed to turn OFF once the Engine Compartment temperature drops below a given threshold - 185°F (85°C).

Unless there is a Heat source adding additional heat, the Fan should remain OFF once the temp drops below the threshold.

What I suspect is that your Fan is turning OFF prematurely before dropping below this temp threshold. I suspect the reason for this is a bad Relay.

The failing Relay heats up when energized and causes the armature to disengage, breaking the circuit and shutting off the Fan. Once the Relay cools sufficiently, the armature re-engages, closes the circuit and starts the Fan back up because the Engine Compartment temp remains above the nominal temp threshold. This cycle continues until the required Engine Compartment temp is achieved, explaining the multiple ON/OFF cycles.

Replacing the Relay is a simple DIY project - pull out the old one and insert the new one. Cost is $7-$24 USD for the part depending upon whether you source the part from Porsche or not. It is Relay #8 (2nd from the Left on the Bottom Row) in the rear Relay Block. Hope this helps...

Happy Motoring!... Jim'99

11-11-2006, 11:47 AM	#9
MNBoxster Registered User Join Date: Sep 2005 Location: Minneapolis/St. Paul, Minnesota, USA Posts: 3,308	Hi, The Engine Compartment Purge Fan (Porsche Parlance) certainly can come ON/OFF multiple times, but should it? The Fan is supposed to turn OFF once the Engine Compartment temperature drops below a given threshold - 185°F (85°C). Unless there is a Heat source adding additional heat, the Fan should remain OFF once the temp drops below the threshold. What I suspect is that your Fan is turning OFF prematurely before dropping below this temp threshold. I suspect the reason for this is a bad Relay. The failing Relay heats up when energized and causes the armature to disengage, breaking the circuit and shutting off the Fan. Once the Relay cools sufficiently, the armature re-engages, closes the circuit and starts the Fan back up because the Engine Compartment temp remains above the nominal temp threshold. This cycle continues until the required Engine Compartment temp is achieved, explaining the multiple ON/OFF cycles. Replacing the Relay is a simple DIY project - pull out the old one and insert the new one. Cost is $7-$24 USD for the part depending upon whether you source the part from Porsche or not. It is Relay #8 (2nd from the Left on the Bottom Row) in the rear Relay Block. Hope this helps... Happy Motoring!... Jim'99 Last edited by MNBoxster; 11-12-2006 at 09:35 AM.