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jchapura

Is there a way to set the radiator fan turn-on temperature to a lower

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I'd like to turn on the radiator fans at about a temperature that's 10 degrees cooler than what they currently turn on at.

 

Is there a way to do that? Different temp switch? Reprogramming one of the computers? If reprogramming, can the Durametric Enthusiast do the job or is the Pro needed? Or some other available tool?

 

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I'd like to turn on the radiator fans at about a temperature that's 10 degrees cooler than what they currently turn on at.
 
Is there a way to do that? Different temp switch? Reprogramming one of the computers? If reprogramming, can the Durametric Enthusiast do the job or is the Pro needed? Or some other available tool?

 

 

In a word, no.  The fan on temps are built into the DME base coding and cannot be altered by either a PIWIS or Durametric system.

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Is there a way to fake the system? Pre-heat it, or more precisely, supplement heat it, perhaps? Or change out the sender/sensor? Where is the temp sensor that it reads for the control temperature? Maybe a resistor or active component could be added to the sensors lead, depending on the type of signal (if it's PID, for example)?

 

Or maybe, I could just put add my own manual/toggle switch and power feed? How hard might that be?

 

It seems that a low temperature thermostat couldn't be fully taken advantage of, in stop-and-go traffic, in hot ambient conditions, because the air may only be flowing when the system hits the factory-set temp of 200, 205 or something like that...

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Is there a way to fake the system? Pre-heat it, or more precisely, supplement heat it, perhaps? Or change out the sender/sensor? Where is the temp sensor that it reads for the control temperature? Maybe a resistor or active component could be added to the sensors lead, depending on the type of signal (if it's PID, for example)?

 

Or maybe, I could just put add my own manual/toggle switch and power feed? How hard might that be?

 

It seems that a low temperature thermostat couldn't be fully taken advantage of, in stop-and-go traffic, in hot ambient conditions, because the air may only be flowing when the system hits the factory-set temp of 200, 205 or something like that...

 

Well, the system uses the same temperature sensor that runs your dash temp gauge, so altering one would change both, which might not be as useful.

 

Some track rats have wired up a manual override switch to force the fans to run, which does not interfere with the automatic system, so that might be a pathway.

 

Another way to go would be to add a third radiator up front, which significantly increases the heat transfer capacity of the car, but is going to require more effort and expense.

 

Are you sure your radiators are clean?  You would be surprised at what we find when we open up a car with overheating problems.

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I'm not sure about their cleanliness. I suspect they are dirty because of the much better temperature control when the ambient temperature is cooler (and less air flow is needed because of the delta T). I hope to clean them this weekend and avoid any mods.

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You might be surprised what you find in there, we actually found a dead bird once:

 

14735d1308958323-radiator-cleaning-radia

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Actually, I want to be surprised (that might explain why even a little bit of spirited driving seemingly spikes the oil temperature, especially during warmer ambient temps). :) Mine look less dirty on the outside compared to your pic but I'm worried what will be trapped between the condenser and radiator.

 

BTW, do you know what (sensor) criteria is used for the computer to turn on the engine compartment exhaust fan? Is it as simple as an ambient temperature greater than 80 deg F?

 

I noticed today when I came to the car after work - I park in an underground parking garage - the dash temp was reading 81 and the exhaust fan immediately started up when the I started the car.

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Actually, I want to be surprised (that might explain why even a little bit of spirited driving seemingly spikes the oil temperature, especially during warmer ambient temps). :) Mine look less dirty on the outside compared to your pic but I'm worried what will be trapped between the condenser and radiator.

 

BTW, do you know what (sensor) criteria is used for the computer to turn on the engine compartment exhaust fan? Is it as simple as an ambient temperature greater than 80 deg F?

 

I noticed today when I came to the car after work - I park in an underground parking garage - the dash temp was reading 81 and the exhaust fan immediately started up when the I started the car.

 

The engine compartment fan is controlled by a temp sensor mounted near the intake manifold, or the coolant temp sensor itself, that triggers the fan when:

 

"Switch-on conditions for engine compartment fan (this fan pulls air into the engine compartment) The engine compartment fan is switched on when the engine compartment temperature is > 176 degrees F or the coolant temperature is > 216 degrees F.

After-running of engine compartment fan If the ignition is switched off and the engine compartment temperature is more than 140 degrees F, the DME control module remains in readiness for another 20 minutes. During this time, the engine compartment temperature is retrieved every 10 seconds. If the engine compartment temperature is > 185 degrees F , the engine compartment fan is switched on for 20 seconds. If the engine compartment temperature is still > 185 degrees F after this time, the fan remains on for a further 30 seconds."

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BTW, do you know what (sensor) criteria is used for the computer to turn on the engine compartment exhaust fan? Is it as simple as an ambient temperature greater than 80 deg F?

 

The engine compartment fan is not an exhaust fan - it pulls cool air INTO the engine compartment.

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JFP.... I have a 08 C4 cab.  In my opinion, the engine compartment fan is not working as intended.  After the engine is warm to normal operating temp and I turn engine off, when I restart engine, anywhere from 20 mins to 2 hours later, the engine compartment fan immediately comes on and if it's still on when I turn engine off again the fan will immediately stop.

 

Once on and driving, the fan will stay on for anywhere from 5 mins to 1/2 hour or longer depending on type of driving, ie  high speed or in traffic etc.   This process will repeat itself everytime I stop and restart the engine until the engine has cooled overnight.  First start in the morning does not start the fan but the on/off process will start with the first off/on ignition cycle I've described.   The fan is never on when the ignition is off.  Even if the fan is on when I turn off the ignition the fan will stop immediately.  

 

The Porsche dealership says this is normal but I have my doubts.  I've owned a 02 C4 and an 04 C4S which have the same 996 engine as my 08 and never had this issue before now.

Since your post has the engine fan's performance citeria in quotes, I'm assuming that you found the info in some authoritative source.

 

Could you please provide that source to me and offer any comments you might have about this fan and how it's operating. 

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In the engine compartment, mounted on the intake manifold, is the temperature sensor for the fan:

 

pic01.jpg

 

It is possible that this sensor has either fallen off its mount (common) and is laying on something hot, or is going bad.  I'd start there.

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Check your engine temp sensor. It may have fallen off and is laying on top of the engine.The sensor is between the intake manifold runners for cylinders #4 and #5. Right side of the engine compartment.

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I've looked for the sensor in the area you described and there is nothing between the intake manifolds for cylinders #4 and #5.  Is it possible not even and sensor "holder" is there? Does a holder for the sensor exist?  I'll take it back to Porsche and ask them to "test the sensor" for me.  

 

A little background on the car FYI.  I purchased the car CPO'd in Dec 2015 when it had only 5k miles on it.   After 3 weeks and 1k miles, the car had two problems I noted.  One was the fan issue and the other turned out to be a badly scored #6 cylinder (excessive oil consumption and badly sooted left exhaust tip).  In my concern about the cylinder issue symptoms,  I failed to mention the fan issue when I brought the car in for service.  As it turned out, Porsche replaced the short block under warranty and the car runs fine but I still have the fan issue.  I did bring the car back for a summer tire change and it was then I was told the fan was operating normally.    Given the lack of a sensor in the area you described, it seems to me it probably wasn't there at time of purchase and overlooked when the new block was installed.

FYI, the purchasing Porsche dealership who CPO'd the car is different than the servicing Porsche dealership.  So if correct, both dealerships missed the lack of sensor when doing some serious maintenance work. ( CPO and a new short block).   Thanks for your help.

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The holder for the sensor is a rubber grommet that slips inbetween the manifold runners the sensor slips into the center.  Nothing exotic, but it is essential.  Look under the intake runners for both the sensor and the grommet, they are both very easy to knock loose.

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Oh never mind. Saw it's an '08 now. Look around for an unconnnect plug then. Maybe the sensor was never installed after the engine rebuilt.

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This is a follow up to my engine compartment blower problem I described above and would appreciate some advice regarding what the local Porsche dealer advised after bringing the car in for service.  Quite frankly I was surprised by their conclusion.

 

The dealership agreed that the blower was operating continually when the ignition was on and never operating when the ignition was off.  Once the engine has gotten past the initial morning cold start, the blower would go on and off every time the ignition went on and off irrespective of the oil/coolant temp at the time of turning the ignition on.  Once on, the blower will stay on no matter what type if driving,( local stop and go, 80mph on highway, etc. )  

 

The service manager advised the blower was operating within the designed parameters.  (BTW he insisted the blower is an exhaust fan removing hot air from the compartment not blowing air into the compartment).

 

He provided the following written description from official Porsche literature. (Sorry Its a bit lengthy but want to ensure you see the full description)

 

"The engine compartment blower on the engine compartment lid is activated in two stages.

 

Stage 1​ (permanent operation) is activated by the fuel pump relay as well as a change over relay and shutoff relay.  Behind the fuel pump relay, a resistance lead (limiting the power to approx. 10 watts) leads to the engine-compartment blower via the shutoff relay.

 

In stage 2, ​the engine compartment blower is activated directly by the Motronic control module via the change over relay and the shutoff relay (power approx. 33W) depending on coolant temperature, engine temperature and the ratio between intake and ambient air temperature.  Stage 2 is also activated during sporty acceleration when detected by the Motronic control module.  Once the temperatures fall below the respective temperature parameters, the engine compartment blower is set back to stage 1.

 

If the engine compartment lid is opened while the engine compartment blower is active, the shutoff relay deactivates the engine compartment blower. 

 

After the engine is switched off , the engine compartment blower may continue to run or start to run.

 

If no reduction of temperature is detected after 5 minutes of the engine compartment bower running in stage 2, the temperature display in the instrument cluster starts flashing.  Additionally, a 'Failure - engine compartment blower" warning is displayed in the on-board computer. "

 

After providing me this written document , the service manager advises the blower was working in accordance with parameters because:

a) Under stage 1, the phase "permanent operation" means the blower can and will continually run at all times while the engine is running

b) The is no set requirement for the blower to come on after ignition is off because the blower "may continue to run or start to run".  This explains why it never comes on when the ignition is off.

 

Also, since they believe the blower is operating within designed parameters, they will not examine any parts related to the operation of the blower. BTW there is no sensor in the position that JFP's picture depicts.  I was told the sensor is between #5 and #6 and is inverted compared to JFPs pic so it's not easily visible looking into the compartment.

 

Upon receiving the response, I was at a complete loss for words at the absurdity of this so I said goodbye and took my car home. The car is CPO'd and fortunately there are other Porsche dealers near by and will take the car to one of them armed with this dealers response and request confirmation.

 

In the meantime, since I'm not a mechanic, could some of you please confirm my conclusions that this is absurd and I should pursue this with another dealer or is there somewhere in Porsche NA I could elevate this to.

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The dealer's description of the engine compartment fan operation is correct for a 997-1.

However I believe he is incorrect about the direction. In all other Porsche 911 series cars the engine compartment fan pulls cool air "into" the engine compartment forcing hot air out.

This is easily tested by placing a tissue paper on the engine cover when it is on - if it is sucked down to the engine lid then it is pulling cool air in -- if it blows away then it working as an exhaust fan.

 

This is the temperature sensor location on late model 997-1.

 

(click to enlarge)

post-1-0-60197700-1465047682_thumb.png

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Thanks for the prompt reply Loren.   So you agree with the dealership that in stage 1 the fan is always on and running and is the reason the fan starts and stops with each on/off ignition irrespective of the oil/coolant/outside air temp.  What then is stage 2?   This would seem to imply that once stage 2 is activated because of a >max temp determination a different fan speed then engages (?) and runs until the max temp is lowered.  The fan then reverts back to the stage 1 speed and continues to run at that speed as long as the engine is running. I was unaware the fan is always on and never stops blowing air into the compartment while the car is running.   The dealer and you are both saying this is the way the fan is designed to operate.  Correct?

 

I've owned three 911s  (02 C4, 04 C4S and this 08 C4) with the M96 engine as daily drivers for the last 12 years.  The first 2 911s which I drove for 11 of those years did not have a compartment fan that was always running.  Do you know if the fan operation changed with the 997.1 M96?

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Thanks for the prompt reply Loren.   So you agree with the dealership that in stage 1 the fan is always on and running and is the reason the fan starts and stops with each on/off ignition irrespective of the oil/coolant/outside air temp.  What then is stage 2?   This would seem to imply that once stage 2 is activated because of a >max temp determination a different fan speed then engages (?) and runs until the max temp is lowered.  The fan then reverts back to the stage 1 speed and continues to run at that speed as long as the engine is running. I was unaware the fan is always on and never stops blowing air into the compartment while the car is running.   The dealer and you are both saying this is the way the fan is designed to operate.  Correct?

 

I've owned three 911s  (02 C4, 04 C4S and this 08 C4) with the M96 engine as daily drivers for the last 12 years.  The first 2 911s which I drove for 11 of those years did not have a compartment fan that was always running.  Do you know if the fan operation changed with the 997.1 M96?

 

Yes.

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Yes, the engine compartment fan operation did change from 996 to 997-1.

 

From the Porsche Tech book

"In stage 2, the engine-compartment blower is activated directly by the Motronic control module via the changer relay and the shutoff relay (power approx. 33W) in dependence of coolant temperature, engine temperature and a ratio between intake and ambient air temperature. Stage 2 is also activated during sporty acceleration when detected by the Motronic control module.

Once temperatures fall below the respective temperature parameters, the engine compartment blower is set back to stage 1."

 

"If the engine compartment lid is opened while the engine-compartment blower is active, the shutoff relay deactivates the engine-compartment blower. After the engine is switched off, the engine compartment temperature is monitored for approx. 30 minutes. During this period, and depending on temperature, the engine-compartment blower may continue to run or start to run.

 

If no reduction of temperature is detected after 5 minutes of the engine compartment blower running in stage 2, the temperature warning light of the coolant temperature display in the instrument cluster starts flashing. Additionally, a “Failure - engine-compartment blower” warning is displayed in the on-board
computer."

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Loren/JFP   Thank you both for your comments. They're very helpful.  I plan to take the car to another dealer to have them advise on the proper location of the sensor.  It certainly not where JFP's diagram indicates.

 

If I may ask one other point.  Are either of you familiar with the "Recall campaign W737- deactivate speed setting 1 of the engine compartment blower"?  I found this in the rennlist 997 forum but it didn't have a lot of commenting except that some members did receive a recall notice. 

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Loren/JFP   Thank you both for your comments. They're very helpful.  I plan to take the car to another dealer to have them advise on the proper location of the sensor.  It certainly not where JFP's diagram indicates.

 

If I may ask one other point.  Are either of you familiar with the "Recall campaign W737- deactivate speed setting 1 of the engine compartment blower"?  I found this in the rennlist 997 forum but it didn't have a lot of commenting except that some members did receive a recall notice. 

 

You should have the dealer check your VIN to see if that recall applies to your car.  It may not.

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