Radiator cooling fan question (yup, I searched!)

[BruceP]

I have a '00 C2, 6-speed, Canada version. I keep an eye on the operating temperature, using the OBD hack rather than the gage. In traffic, the car has always run pretty warm, regularly over 100 C in the spring-summer-fall. Last night, it was up over 105 C, and I thought I'd hop out and check to see if the cooling fans had switched to high speed as they are supposed to at this temperature. On the passenger side of the car, the fan was loud and you could feel air being moved. On the driver side, the fan was on but quieter, and less air was moving.

Is this normal? If not, can you suggest an explanation? I can imagine losing a fan altogether, but I can't figure out why it would just refuse to switch speeds.

TIA,

Bruce.

Edited May 27, 2008 by BruceP

[Loren]

:welcome:

http://www.renntech.org/forums/index.php?s...p;hl=fan++speed

http://www.renntech.org/forums/index.php?s...p;hl=fan++speed

http://www.renntech.org/forums/index.php?s...p;hl=fan++speed

http://www.renntech.org/forums/index.php?s...p;hl=fan++speed

and many more...

[BruceP]

Who knew! I was avoiding using search criteria this specific! Thank you, Loren. Looks like the search begins at the fuse panel...

Bruce.

[juniinc]

I would start t car when she is cool, turn the AC on, go check 2 front fans, any difference I would search

[BruceP]

Relays and fuses all checked out. I took it into the dealer thinking the resistor would be the culprit, but it turns out I need whole new fan. So that's the end of the story, for whatever use it may be to others. Two thoughts:

Knowing how to get the actual temperature reading from the OBD was very helpful to me. Without that trick and this forum, I might never have realized I had a problem.

And I'm going to assume that spending a bunch of time running at 105-108 C won't have any long term ill effects? If something was going to go boom, it would have by now?

Thanks to those who replied.

[flyingpenguin]

Interesting...

You mention that you keep an eye on operating temp with the OBD hack. I have the hack working and can toggle (with the switch on the dash, not the 4th stalk) from outside temp, to miles till empty, to AVG MPG and to something else (>MPH, ever wondered what that's for?).

Never have I seen the operating temp in that cycle. Looking forward to do this.

Joost

[zoomsan]

Relays and fuses all checked out. I took it into the dealer thinking the resistor would be the culprit, but it turns out I need whole new fan. So that's the end of the story, for whatever use it may be to others. Two thoughts:

Knowing how to get the actual temperature reading from the OBD was very helpful to me. Without that trick and this forum, I might never have realized I had a problem.

And I'm going to assume that spending a bunch of time running at 105-108 C won't have any long term ill effects? If something was going to go boom, it would have by now?

Thanks to those who replied.

Hi...would you mind elaborating on the OBD hack? I tried a search and couldn't ID how to do this. Thanks!

[OCNYPORSCHE]

Interesting...

You mention that you keep an eye on operating temp with the OBD hack. I have the hack working and can toggle (with the switch on the dash, not the 4th stalk) from outside temp, to miles till empty, to AVG MPG and to something else (>MPH, ever wondered what that's for?).

Never have I seen the operating temp in that cycle. Looking forward to do this.

Joost

There are 2 "hacks". One is a "hack" that involves a certain sequence that results in a digital display of the temperature on the heating/cooling controls. The OBC is the On Board Computer mod that either involves the 4th stalk, or a switch.

[flyingpenguin]

I have the switch. Does anyone know the sequence?

Rgds, Joost

[flyingpenguin]

This is what I found on rennlist:

http://forums.rennlist.com/rennforums/show...amp;postcount=2

It does not use the OBC but the AC display. Lots of very useful stuff!

I found though that on my 2000 996 C2, the sequence to shift between F and C is "recirc" and "temp+" (not both "temp+" and "temp-" together).

Joost

[BruceP]

OBD=On Board Diagnostics. To the best of my knowledge, the information is not available through the onboard computer.

These are the instructions: On your climate control panel, press and hold in the recirculate and the top (arrow up) buttons on the right side of the panel for a few seconds. The left screen will change. Using the + key below that screen, advance so the display reads 6c. Then press the center vent button once. The display will show you your coolant temp.

To restore your climate control display, press the Auto button.

If you don't change the temperature display while you're in OBD mode, all you have to do to get it back is hold the arrow up and recirc buttons in for a few seconds, and it will default to the temperature display. If you do this again later during the same trip, the temp will display instantly, which is handy for hard sessions.

Again, I really found this useful. It seems like things have to get pretty hot before the car will let you know there's a problem by itself. I'd still be sitting in traffic at 108C without forums like this.

PS I believe that this doesn't work - or work the same way - on Mk. 2 cars. Perhaps an expert can chime in.

Edited June 5, 2008 by BruceP

[flyingpenguin]

In 100 F Houston weather, stop & go traffic with AC blowing full, I have seen 110 C on the coolant temp (C6). From the previous post I understand that should be a problem.

Can anyone chime in here?

Joost

Edited June 5, 2008 by jperquin

[1999Porsche911]

In 100 F Houston weather, stop & go traffic with AC blowing full, I have seen 110 C on the coolant temp (C6). From the previous post I understand that should be a problem.

Can anyone chime in here?

Joost

Your goal is to keep the engine from getting to that temperature in the frst place. You can do my fan mod which allows you to turn the fans on full speed with a flip of a switch and you will be able to control engine temps in stop and go driving.

Radiator Fan and Engine Compartment Fan Switch Mod

The 3.4 996 runs extremely hot when driving around town in temperatures higher than 75 degrees. This mod is a way to reduce coolant temps back to a safer level, helping to reduce oil temps and improving performance.

The mod consists of installing a switch that will allow you to turn on the high speed radiator fans at any time, while maintaining the automatic operation of the fans. We do the same for the engine compartment fan.

Radiator Fans

Connect a wire to the ground (Pin #85) of the 2 high speed fan relays located on the relay carrier located in the driver’s side foot well. The relays are #20 and #22. Feed this wire to where your switch will be located. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and then connect the other end of this wire to a chassis ground point.

With key on, this switch will now immediately turn on both radiator fans providing maximum cooling. When you turn the key off, the fans will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off.

Engine Compartment Fan

Connect a wire to the ground of the relay located in the relay carrier behind the passenger seat, driver’s side. Relay #8. . Feed this wire to where your switch will be located. I simply fed the wire along the driver’s side of the car and under the door sill. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and connect the other end of this wire to a chassis ground point.

With key on, this switch will now immediately turn on the fan drawing air into the engine compartment. When you turn the key off, the fan will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. This mod helps keep the engine compartment much cooler when driving around town and is particularly beneficial to any engine that draws its intake air from inside the engine compartment. It will also help keep engine temps down.

If you are adventurous, you can automate the operation of these switches so they will switch off at a specific speed, or operate when vacuum is present only, etc. You can choose any style switch you want and even use Porsche switches. I simply used 2 toggle switches that I installed in the batwing,

Jim

[flyingpenguin]

In 100 F Houston weather, stop & go traffic with AC blowing full, I have seen 110 C on the coolant temp (C6). From the previous post I understand that should be a problem.

Can anyone chime in here?

Joost

Your goal is to keep the engine from getting to that temperature in the frst place. You can do my fan mod which allows you to turn the fans on full speed with a flip of a switch and you will be able to control engine temps in stop and go driving.

Radiator Fan and Engine Compartment Fan Switch Mod

The 3.4 996 runs extremely hot when driving around town in temperatures higher than 75 degrees. This mod is a way to reduce coolant temps back to a safer level, helping to reduce oil temps and improving performance.

The mod consists of installing a switch that will allow you to turn on the high speed radiator fans at any time, while maintaining the automatic operation of the fans. We do the same for the engine compartment fan.

Radiator Fans

Connect a wire to the ground (Pin #85) of the 2 high speed fan relays located on the relay carrier located in the driver’s side foot well. The relays are #20 and #22. Feed this wire to where your switch will be located. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and then connect the other end of this wire to a chassis ground point.

With key on, this switch will now immediately turn on both radiator fans providing maximum cooling. When you turn the key off, the fans will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off.

Engine Compartment Fan

Connect a wire to the ground of the relay located in the relay carrier behind the passenger seat, driver’s side. Relay #8. . Feed this wire to where your switch will be located. I simply fed the wire along the driver’s side of the car and under the door sill. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and connect the other end of this wire to a chassis ground point.

With key on, this switch will now immediately turn on the fan drawing air into the engine compartment. When you turn the key off, the fan will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. This mod helps keep the engine compartment much cooler when driving around town and is particularly beneficial to any engine that draws its intake air from inside the engine compartment. It will also help keep engine temps down.

If you are adventurous, you can automate the operation of these switches so they will switch off at a specific speed, or operate when vacuum is present only, etc. You can choose any style switch you want and even use Porsche switches. I simply used 2 toggle switches that I installed in the batwing,

Jim

Very useful write-up!

I installed the 3rd radiator but in stop-and-go traffic, temps (even now that we're entering winter) still reach 100C and higher, so I guess I am going to do your mod soon.

Any input as to which of the two mods gets you the biggest bang for the effort? I have a hunch that the high speed fans provide more cooling than the engine compartment fan. Correct?

Joost

Edited December 3, 2008 by jperquin

[1999Porsche911]

In 100 F Houston weather, stop & go traffic with AC blowing full, I have seen 110 C on the coolant temp (C6). From the previous post I understand that should be a problem.

Can anyone chime in here?

Joost

Your goal is to keep the engine from getting to that temperature in the frst place. You can do my fan mod which allows you to turn the fans on full speed with a flip of a switch and you will be able to control engine temps in stop and go driving.

Radiator Fan and Engine Compartment Fan Switch Mod

The 3.4 996 runs extremely hot when driving around town in temperatures higher than 75 degrees. This mod is a way to reduce coolant temps back to a safer level, helping to reduce oil temps and improving performance.

The mod consists of installing a switch that will allow you to turn on the high speed radiator fans at any time, while maintaining the automatic operation of the fans. We do the same for the engine compartment fan.

Radiator Fans

Connect a wire to the ground (Pin #85) of the 2 high speed fan relays located on the relay carrier located in the driver’s side foot well. The relays are #20 and #22. Feed this wire to where your switch will be located. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and then connect the other end of this wire to a chassis ground point.

With key on, this switch will now immediately turn on both radiator fans providing maximum cooling. When you turn the key off, the fans will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off.

Engine Compartment Fan

Connect a wire to the ground of the relay located in the relay carrier behind the passenger seat, driver’s side. Relay #8. . Feed this wire to where your switch will be located. I simply fed the wire along the driver’s side of the car and under the door sill. Connect the wire to one side of the switch. Connect another wire from the other contact on the switch and connect the other end of this wire to a chassis ground point.

With key on, this switch will now immediately turn on the fan drawing air into the engine compartment. When you turn the key off, the fan will continue to run for about 5 seconds until the relay shuts down. Your fan operation remains normal when the switch is off. This mod helps keep the engine compartment much cooler when driving around town and is particularly beneficial to any engine that draws its intake air from inside the engine compartment. It will also help keep engine temps down.

If you are adventurous, you can automate the operation of these switches so they will switch off at a specific speed, or operate when vacuum is present only, etc. You can choose any style switch you want and even use Porsche switches. I simply used 2 toggle switches that I installed in the batwing,

Jim

Very useful write-up!

I installed the 3rd radiator but in stop-and-go traffic, temps (even now that we're entering winter) still reach 100C and higher, so I guess I am going to do your mod soon.

Any input as to which of the two mods gets you the biggest bang for the effort? I have a hunch that the high speed fans provide more cooling than the engine compartment fan. Correct?

Joost

Running the radiator fans provide the most cooling.

[flyingpenguin]

Jim.

I finally got to install your mod for the radiator fans. Pretty easy to wiggle the wires onto pin #85 on the relays...

I got the footwell light toggle switch (996 613 980 00) to control on/off for the fans, but am at a loss now, as this switch only keeps the fans running while you keep the switch depressed. Did I get the wrong switch?

Is there a trick to wire it differently (I used the two horizontal and vertical fins in the middle of the switch) or should I get a different toggle switch?

Joost

Edited February 23, 2009 by jperquin

[dammad]

What temperature is a 3.4 996 supposed to run at? Mine says 101C. Seems reasonable (just around boiling).

[flyingpenguin]

What temperature is a 3.4 996 supposed to run at? Mine says 101C. Seems reasonable (just around boiling).

Low 90's C is more normal.

JP

[dammad]

some information based on my investigations for future members with overheating:

(1) AC coolant temp hack (6c) isn't very representative of current coolant temperature. When comparing with the OBD2 figures, the AC figure is a running average and 1-2C higher than OBD2 coolant temp (PID 0x05).

(2) If you remove the relays for the low speed fans (drivers footwell), the high speed fans will cycle on/off with a 2-3 minute interval from cold. This is a real easy way to see if the high speed fans and how noisy they are.

(3) Slight pressure leaks in the coolant system can allow the system to not fully pressurize. If things are running hot, clean the rads and check for slight leaks on the coolant (for example the tanks are prone to go).

(4) On my 99 according to the OBD2 numbers, the low speed fans come on at 100C and turn off again at 96C. I assume the DME has a more direct sensor value, so 100C on the OBD2 might be 96.75C to the DME.

[Stefan]

If you don't want to have to operate a manual switch you can try my radiator cooling fan hack. It should take about 5 minutes to implement.

http://www.ppbb.com/boards/ppbbphp/showfla...;Number=1509504

[1999Porsche911]

If you don't want to have to operate a manual switch you can try my radiator cooling fan hack. It should take about 5 minutes to implement.

http://www.ppbb.com/boards/ppbbphp/showfla...;Number=1509504

The switch in my fan mod is not to correct a non functioning fan system or relay. Fixing the relay fault is quite simple and should be done with new relays when necessary. The fan mod is to turn on the HIGH speed fans at will and at any temperature. Or you can eliminate the switch altogether and have the high speed fans come on below a certain engine speed, vehicle speed, etc.

[Stefan]

My fan mod is not intended to fix a broken relay. It is intended to fix a broken ballast resistor, which is a common problem and the source of many cars running too hot. It works automatically and without the driver having to think about it. Fixing a relay is trivial but fixing the ballast resistor is more involved and requires buying a fairly expensive part.

If you don't want to have to operate a manual switch you can try my radiator cooling fan hack. It should take about 5 minutes to implement.

http://www.ppbb.com/boards/ppbbphp/showfla...;Number=1509504

The switch in my fan mod is not to correct a non functioning fan system or relay. Fixing the relay fault is quite simple and should be done with new relays when necessary. The fan mod is to turn on the HIGH speed fans at will and at any temperature. Or you can eliminate the switch altogether and have the high speed fans come on below a certain engine speed, vehicle speed, etc.

[wwest]

In 100 F Houston weather, stop & go traffic with AC blowing full, I have seen 110 C on the coolant temp (C6). From the previous post I understand that should be a problem.

Can anyone chime in here?

Joost

Yes.

I would check that both front radiator fans are fully operational.

But in the meantime, or otherwise......

Turn the system to maximum cooling ("lo" in the temperature "set" window), recirculate mode, and lower the blower speed to your comfort level noise wise. Once the cabin is cooled to your comfort level adjust the blower speed manually to maintain that level.

Also be sure, certain sure, the windshield duct (defrost/defog/demist) airflow mode is NOT in automatic via manually turning it OFF(!!) otherwise you suddenly may find yourself absent any forward vision on a HOT but humid day in Houston. For some reason the Porsche engineers have missed a HUGE flaw in the design of the A/C, once the cabin is cooled to your setpoint a substantial level of COOLED airflow will be routed from the windshield ducts and then COOL the windshield to a level wherein on a HUMID day (or night, even worse!) condensation will begin to form on the outside.

VW saw fit to fix this flaw on their version of the Cayenne but Porsche even refuses to acknowledge the problem/issue exists. "Operating as designed".

Using the above control technique you will have bypassed the system's reheat/remix mode thereby raising the AC efficiency substantially. Fewer A/C compressor cycles will result in a lower heat load on the engine coolant radiator and slightly improved FE to boot.

You can avoid this procedure by going to Home Depot and purchasing a water flow shutoff valve to insert in the coolant line to the heater. During the summer months simply turn off the flow to the heater core. Additionally I installed a switch in the A/C compressor clutch circuit so I can prevent the A/C from operating unless I actually need cooling, or initial cooldown.

[GranburyChuck]

Stefan, does your mod then make the fan automatically go to high speed mode or does the low speed operate first? Just wondering if the fans will be on high speed all the time in north Texas as temps are in the 100s and I will be driving with the AC on.

[Stefan]

With my mod, the low fan speed is replaced with high fan speed. It should generally make the car run cooler. With the A/C on the fans are normally low speed (until the coolant temp gets above 206°F). With my hack, and the A/C on the fans will run at high speed all of the time.