Engine Compartment Fan Manual Switch - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Here is how to install a switch that will allow manual control of the engine compartment fan. This is not for the radiator fans at the front of the car but rather the fan that cools the engine compartment by drawing in air through the passenger side vent in the rear fender (engine intake is on drivers side, engine compartment fan is on the passenger side). I wanted to manually control the fan at the race track on hot days to provide additional cooling to the engine and engine compartment after coming into the pits after a track session. It is fairly easy to tap into the engine compartment fan relay. The difficulty in this job will come from deciding where to mount the switch and running the wires from the rear trunk to the switch location. In the case of my Spec Boxster race car, I was fine with installing the switch in the rear relay tray. To switch the fan on at the track, I just open the rear trunk and hit the switch on or off. Here is how the engine compartment fan works; Engine Compartment Purge Fan To reduce the temperature of the engine compartment, a fan actuated by the DME is installed behind the ventilation grille of the passenger side rear fender vent. If the fan is active, fresh air is fed into the engine compartment. There is a temperature sensor mounted in the engine compartment to provide temperature input to the DME. Standard Operation: 1. With engine running or ignition on: If the engine temperature is higher than 102° C and the engine compartment temperature is higher than 60°C, the engine compartment fan is switched on for 30 seconds by the DME control unit and the engine compartment is thus ventilated. 2. With the engine off and vehicle is stationary: If the engine compartment temperature is higher than 60° C when the engine is switched off (ignition off) or if the engine stalls (engine speed: 0 rpm), the engine compartment fan is switched on for 20 mins. Note: If the engine temperature has not dropped below 80.25°C after the engine compartment fan has been running for 25 seconds, a fan fault is registered and the coolant level warning lamp is activated (flashes). To install a manual control switch: Open the rear trunk and locate the rear relay panel. It is tucked way, way, way up under the driver side fender. You will have to pull back the trunk carpet/lining and look inside the fender well to see it. Remove the two screws holding the relay panel and slide it out towards the center of the trunk. It may take some pulling on each side to get the relay panel to slide out. Be careful not to break the plastic relay tray. Continue to pull the relay tray from its sliders. Now the relay tray should be clearly in view. The engine compartment fan is controlled by relay #8. This relay is a standard Type 53 used throughout the Boxster. To test the engine compartment fan, simply jumper relay pins 30 and 87 as shown below. The engine compartment fan should turn on. Remove the relay and install one pin tap at pin 30 and a pin tap at pin 87, bend over at 90 degrees so the blade will come out from the underside of the relay and re-install the relay. Here is an example of a pin tap on a fuse. They are easily modified for use on a relay. Last attach two wires to the pin taps at the relay and then route the wires to the switch to activate or deactivate the engine compartment fan. Alternatively, I could have figured out which pin is ground (30 or 87) and then you'd only need to run one wire from the relay (the non-ground pin) to the switch and the other wire could be grounded locally near the switch.

Quick question, have you had an issues with manually triggering the fan causing the CEL to come on? You mentioned the possibility of a fault code. Great job, and great post! I will be looking into this, my Boxster runs hotter than I would like in the summer.

Nice.......... Tom!

Never heard of pin taps. Who sells them?

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Most auto parts stores stock them. Here are links to AutoZone and Amazon: Dorman/Fuse and Accessories 85606 - Read Reviews on Dorman #85606 http://www.amazon.com/WirthCo-30001-Fuse-Tap-Fuses/dp/B000CQBNFI

Why not tap into the harness wires with wiretaps? Also, you mentioned this was only for cooling down engine bay AFTER the track session. Makes sense, but would there be a benefit in running it DURING the session to help cool airflow around the oil cooler and help keep oil temps down? How many CFMs is the fan?

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The oil cooler is cooled by engine coolant, not air flow. If you want to lower oil temps, use a larger cooler on a base car, or lower the coolant temperatures.

Quotes source post: 514687

My solution simply adds a manual switch to command "On" the relay. Using wiretaps and a switch to go direct to the fan would bypass the relay which is not a very good approach. Relays exist for a reason. How To Use Relays and Why You Need Them

Why not put in an adjustable thermostatically driven relay? Any time you get 60C or more the fan goes on until it comes down to 60C.

Hi, while attempting to get the compartment fan manually working I might have shorted some of the pins of the relay on the picture. The car runs like poo, seems like half bank or half of the cylinders, spoiler went up and doesn't go manually down. Car shows Christmas lights of errors on the dash, for example PSM. I have checked the fuse box under the dash, I couldn't any burned fuses. Anything more to check? What could have gone wrong? Any diagrams I can get? I am puzzled how any of the relay pins could have messed up with electronics and hopefully not a damaged ECU.

So I'm still thinking and investigating what could have gone wrong. on the list to do: check for error codes and reset check 40a fuse on relays check maf / try run engine with maf disconnected check coils possible variocam solenoid that would only partially cover engine missfires but what about PSM, ABS, spoiler lights?

Those relays run straight back to the ecu. Did you have the battery disconnected while working on the pins? I understand the reason for testing the pins to confirm their function but it's quite risky doing any kind of work like this with the battery connected. Check your wiring harness, something may have been dislodged. Otherwise you may have a big problem.. Sent from my POCOPHONE F1 using Tapatalk

ike84, No battery wasn't disconnected as I was going to try run the fan manually. Going back in time, I have realized I have used a +12v connected to the relay pins for a few seconds.. *I have checked for error codes with generic OBD and there are no stored codes, I have performed a reset anyway *checked 40a fuse on relays, its is ok *tried to run engine without maf connected, still same missfires *I have shuffled relays 53 around, also with no luck, spoiler is not responding Any more ideas what could be wrong? still on the list: check coils possible variocam solenoid issue none of them can be easily checked until I flatbed the car to a mechanic I also have another 986S but older from year 2000, I believe I cannot swap ECUs between the two cars, correct? What would be the procedure to swap with a new ECU, get the memory out of the old and reprogram the new one with it? also is a new immobilizer needed in this case?

The way these solenoids work is that a low current actuation (from the ECU) closes a high current circuit (in this case the fan). If you applied 12v back to the ECU lead that would be enough to cause major damage. All it takes is momentary contact to sorry out a circuit. FWIW I have blown plenty of fuses like this, I have certainly learned this lesson the hard way. In my mind I would have a hard time explaining so many problems that simultaneously started with anything but an ecu short. Unless this car is a 2000, a swap from your S will not work. The ECU must match the ME version that is currently running in the car, and that changed from 7.2 to 7.8 in 2001 or 2002, in don't remember off the top of my head (I think 01 cars were wired with can bus systems but the change to 7.8 didn't happen until 02) What I would do is call a reputable company that works on ecu's and describe the situation to them. Ecu doctors is one such company - I have never used them but I have read mostly good things about them. If they think the ECU is the problem there is a chance they can fix it. If the ECU is the problem and it cannot be fixed then you're looking at a hell of a headache. Matching ecu, immobilizer, and keys. If that's the case talk to Woody (itsnotanova) and he may be able to help you locate the parts. Sent from my POCOPHONE F1 using Tapatalk

Sorry for the delay, the problem was fixed few months ago. :ah: It was indeed fried ECU. Instrument cluster and ABS stopped communicating because of a blown fuse ECU was not operating Variocam correctly on each bank leading to missfires, the mechanic has isolated it by disconnecting solenoid from ECU and idle returned back to normal, no missfires. I have since replaced the ECU, reflash with my tune and reprogrammed immobilizer. If anyone interested in the error codes: P9111 PSM/ABS unit / defective communication P9144 PCM unit P9130 Voltage low P9133 BORNE.61 low engine / incorrect signal P1600 timeout CAN PSM P2092 P0300 Missfire detection P0306 Missfire cyl 6 P0304 Missfire cyl 4 P0305 Missfire cyl 5 P0303 Missfire cyl 3 P9114 CAN bus error / defective communication In hope no one else repeats my error