Engine Compartment Fan Running - Part II

[dog4delta]

There's a previous post on this topic that was started on 8 Oct 2009. However, I have a couple of more questions. Here's a link to the previous thread:

http://www.renntech.org/forums/index.php?showtopic=29589

My engine compartment fan now appears to be running all the time, even when I first start the engine and it is cold. However, it's not running at full bore the way it does when it comes on when the engine is hot. I've never noticed it running before with the exception of when it's really moving air due to the engine being hot. At this lower speed, it's still moving some air, but basically just puts out a low volume of air kind of like a small desk fan.

I think I found the thermostat as discussed in the previous post. At least I found a small black sensor that has about a 1/4" diameter round protrusion that is about 1/2" long. It's located just under where the inner-cooler hose plugs into the metal Y-pipe on the right side of the engine, and has a small 2-wire connector plugged into it. When I disconnect the plug and start the car, the fan then runs full speed, so my guess is that it's the temp sensor.

As I just had the air pump out in order to change to a 5 bar fuel pressure regulator, I'm wondering if perhaps I could have messed anything up. However, the plug is definitely connected to the sensor.

Two questions;

(1) Does the engine compartment fan have some intermediate speed(s) or is it either supposed to be on or off?

(2) As the local ambient temp today was in the low 70s and the fan started running (at a low speed) as soon as I started the engine, would the temp sensor be the likely culprit, and if so, is there any way to do a resistance test on it?

Thanks for any help,

Bill

'03 996TT

[Loren]

1. No, it is either on or off.

2. It is rare for the engine purge fan to come on at all.

Have you checked the car for OBD II fault codes?

Many times a faulty sensor (or wiring) will cause a P1675 fault code.

Check the relay also - relay 8 on the DME/Relay panel behind the carpet - behind the rear seats.

Relay 8 will be second row second relay in from the left (996.615.102.00 - same as the rear spoiler relays).

If you are not the first owner perhaps the previous owners jumpered the sensor?

[dog4delta]

Loren,

Thanks for the quick reply.

I am not the original owner, but have owned the car about a year now and have not previously noticed the fan running continuously on this "low" mode.

Also, there are no current or pending codes (I just checked the car again this morning).

I swapped the fan relay with the spoiler relay and the results are the same; the fan runs at a low speed whenever the engine is running. Looking at the diagram on the relay, at appears that the "normal" state of the relay (fan OFF) is continuity between pins 30 and 87a, and the "on" state of the relay (fan ON) is continuity between pins 30 and 87.

With the KEY OFF, pin 30 is to ground, as is pin 87a. I get 12V at pins 86 and 87, and 3.7V at pin 85.

With the KEY ON, ENGINE RUNNING, pin 30 is to ground, and I still get 12V at pins 86 and 87, and 3.7V at pin 85. However, I now get 6.9V at pin 87a, which to me would explain why the fan is running at a low speed. If I disconnect the temp sensor in the engine compartment, the fan runs in a high (normal) state.

One thing I failed to mention in my original post, is that in addition to the FPR change (when all this fan stuff began), I upgraded to a K16/16G turbo configuration and reprogrammed the DME with a new FVD flash. I had been running a FVD flash prior to this updated flash, and the fan did not previously run at a low state. Would the fan now running be perhaps part of the new flash?

I had not thought of that earlier as the previous flash was from FVD and I didn't have any fan issues. If this is perhaps flash related, I'll give FVD a call next week and see if they have this parameter intentionally set this way.

Thanks again for any additional insight you can offer,

Bill

Edited November 14, 2009 by dog4delta

[wvicary]

Something doesn't sound right. On a typical relay, terminal 30 is constant power, 87 is the output for the 30 terminal, 86 is the control power for the relay- as in the power circuit for the solenoid winding and 85 is the ground path for the winding. I haven't checked the wiring diagram for your car but I can't see Porsche deviating from the norm.

[Loren]

The purge fan is controlled by the DME so it is possible that the re-flash caused the problem.

[dog4delta]

OK, I’m stumped . . .

I reflashed the car with the original OEM Porsche (unmodified) file and the engine compartment fan still runs at a low speed anytime the engine is running. I think that pretty much eliminates the FVD flash as the culprit. I’ve been waiting all week to hear back from FVD, but am still waiting as of today.

I was attempting to trouble shoot with a 1999 996 wiring diagram (which is all I have), but alas there are some differences between my relay wiring and what that particular wiring diagram shows. The wiring diagram I was attempting to use shows only 4 pins at the relay (30, 85, 86, 87), and not the 5 that my car has. My car has a pin 87a (not show on the wiring diagram) with an orange/white wire.

When I remove the fan relay the fan stops running, and swapping the fan relay with another relay does nothing to resolve the issue. I therefore do not believe the problem has anything to do with the relay. When I “open” (disconnect) the engine compartment fan temp sensor, the fan runs at “high” speed. If I “jump” the temp sensor connector, the fan runs at a low speed, the same as if the temp sensor is connected, so I don’t think there are any issues in regards to the sensor itself. However, since I don’t have any idea what the nominal resistance of the sensor should be, I can’t be 100% sure.

I went back and double-checked all the fan relay voltages (relay #8) once again and here’s what I got;

Pins 85 & 86 control the relay state and appear to function normally. Pin 86 has 12V at all times (key off or engine running). Pin 85 has 3.6V (key off or engine running) with the exception of when the fan is “commanded” on (fan running full speed) at which point it reads 0.2V.

Pin 87 has 12V at all times as well (key off or engine running or fan running on high). I believe this to be normal. However, I’m pretty confident that the voltage at pin 87a (the mystery wire I can’t trace due to my lack of an appropriate wiring diagram) is causing the fan issue. With the key off, or key on AND engine not running, I get 0V at 87a. However, when I start the engine, I get 7V at 87a and the fan runs at a low speed. I also get 7V at the fan motor itself.

Loren; Any chance you have a wiring diagram for an ’03 Turbo, or can help me figure out where pin 87a (orange / white) is getting voltage from? It appears from the relay diagram that with outputs on pins 87 and 87a, that the relay is made to have two “powered” states and not just a simple on / off. While I never remember the fan running in a low state before, is it possible that I’m chasing a non-existent problem?

Thanks for the continued help,

Bill Underwood

[Loren]

Red/Black goes to fuse B4

Orange/White goes to fuse C5

DME control line

[dog4delta]

Loren,

Thanks for the reply, but it took nearly an hour for you to respond to my last post. Come on now. You must have something better to do than spend Saturday offering your help to others!

The yellow / red wire that runs to the DME and controls the relay functioning makes sense, and is the same as shown in the "incorrect" non-turbo diagram I was using. Also, pin 87 to fuse B4 is the same as is the information you sent.

Pin 87a (orange / white) to fuse C5 is what I needed help with, but now I have yet another question. According to the fuse diagram I have, fuse location C5 is empty. Figuring I might have an incorrect fuse diagram I went looking for another one and found the following;

http://www.renntech.org/forums/index.php?s...hl=fuse+diagram

Fuse location C5 is "empty" on that diagram as well.

In my fuse block in location C5 there is a 5A fuse and yes, it is providing power to the fan when it runs at a slow speed. If I pull it, the fan stops. Now if this is the only thing making my fan run at a low speed, and there's not supposed to be a fuse in position C5, I suspect I could just pull the fuse and be happy. However, I didn't put the fuse there, and as there is something definitely supposed to be wired to that fuse location (according to your above post) I'm not sure that's a good idea. Also, I don't have any "hacked" fuse locations so don't figure power is somehow getting to C5 via a backdoor.

Can you check your wiring diagram and see what's shown in terms of labeling and amperage for fuse block location C5? I'm really more concerned with what source is providing power to C5 (where's the 7V coming from), and if I pull the fuse, am I shutting off power to anything other than the engine compartment fan?

Take the rest of the day off, with pay . . . ;)

R-

Bill

[Loren]

5 Amp

[dog4delta]

Well it looks like fuse location C5 exists on the schematic, even if it's not depicted on the fuse block diagram.

Does your schematic show the power source for C5? It must be a switched power source, as it's only hot for a few seconds when the key is first switched on, and the hot again when the engine is running.

Since C5 does not appear to be the power source for anything other than the engine compartment fan, I suspect I could simply pull it to keep the fan from running at it's current "low" state . . . ?

R-

Bill

[Loren]

Well it looks like fuse location C5 exists on the schematic, even if it's not depicted on the fuse block diagram.

Does your schematic show the power source for C5? It must be a switched power source, as it's only hot for a few seconds when the key is first switched on, and the hot again when the engine is running.

Since C5 does not appear to be the power source for anything other than the engine compartment fan, I suspect I could simply pull it to keep the fan from running at it's current "low" state . . . ?

R-

Bill

Yes, it is switched engine power - it shares the circuit with the fuel pump relay. The fuse is between the fuel pump relay and the engine purge fan.

Sorry, but pulling the fuse does not solve the inherent problem. I would put a PST2 or PIWIS tester on the car and test the circuits and control.

[dog4delta]

Loren,

Looks like a trip to Ruf is in store. Hopefully I don't have a problem somewhere in the wiring harness.

There are a couple of places online that appear to sell Porsche wiring diagrams. Can you perhaps recommend a specific site or vendor.

Thanks again for your quick replies and all the help.

R-

Bill Underwood

[Loren]

Loren,

Looks like a trip to Ruf is in store. Hopefully I don't have a problem somewhere in the wiring harness.

There are a couple of places online that appear to sell Porsche wiring diagrams. Can you perhaps recommend a specific site or vendor.

Thanks again for your quick replies and all the help.

R-

Bill Underwood

PM member Porschelibrarian -- he should be able to help you.

[kosmo96]

I seem to have the same problem and am anxious to hear if you identified the cause and solution. Have you made any progress since the last post?

[dog4delta]

I am now pretty much convinced that I have been chasing a problem that in reality does not exist, at least not on my car. I spoke with the Service Manager at Ruf in Dallas (Hans Hoffmann). To the best of his knowledge, as well as his experience as a previous owner of a 996 Turbo, the engine-compartment fan will run when the engine is running, and not just when the engine compartment temperature gets high. I believe the engine compartment temp sensor turns the fan on “high” when the engine compartment temp gets to 180 deg F. The fan will continue to run on high, even with the engine turned off and key removed, until the temp in the engine compartment falls below 180.

Here’s where I believe some of the confusion originates. The engine compartment fan relay and wiring on a non-turbo 996 is not the same as the relay for the turbo version, at least not between 2000 and 2003 model years. I was originally trying to trouble shoot my “problem” with a wiring diagram from a 2000 996. The relay for the 2000 996 is a simple “on” or “off” relay. In other words, based on the design of the relay the fan will either be running full bore, or be off. There is no intermediate or "low" state. The relay, and hence the fan, is switched on by the DME when the engine compartment temp sensor gets hot enough.

On my 2003 Turbo, the engine compartment fan relay has an “on” or “on” state that is also controlled by the DME. However, in the “normal on” state a lower voltage (7 VDC) is supplied to the engine compartment relay and hence the fan causing it to run at a “low” speed whenever the fuel pump is running (anytime the engine is running or when the ignition is first switched to on). In fact, the power source wired to the “normal on” pin on the relay is taken directly from the fuel pump and is bussed to the relay through fuse C5. The 2000 996 is not wired this way.

To cause even more confusion, this fuse location (C5) on the wiring diagram is labeled as “optional” and is shown as a 5-amp fuse. Why it would be labeled as “optional” I have no idea. It would however tend to make me think that certain cars came with the fuse installed, and perhaps others did not. Also, both of the fuse block diagrams I have found for my car show fuse location C5 as being “empty” and not even labeled. If I remove fuse C5 then my fan only runs on “high” when the engine compartment gets hot. If I put the fuse back in, the fan runs at a low speed at all other times whenever the engine is running. If you have never observed your engine-compartment fan running at anything other than full speed, my guess is that your car has no fuse installed in location C5.

The last bit of information that makes me think my fan is acting normally is taken directly from page 61 of my owner’s manual;

Warning!

Risk of Injury.

The engine-compartment blower always runs when the ignition is switched on. After the ignition is switched off, the engine compartment and coolant temperatures are monitored for approx. 20 minutes. During this period, and depending on temperature, the engine-compartment blower and radiator fans may continue to run or start to run.

Mystery solved . . . ?

And Loren, thanks again for all your help!

[Loren]

I should have looked this up earlier -- sorry.

From the 2001 996TT Service Information Book

"Two-speed engine compartment scavenging blower

To prevent components from heating up excessively especially as a result of radiated heat from the exhaust system, the fuel pump relay immediately activates the engine compartment scavenging blower (stage 1) if the engine is running at idling speed or if the ignition is switched on ( for longer than 1 sec.). Stage 2 is actuated by the engine compartment temperature sensor.

Caution! Safety note:

Special care must be taken when working on components in the engine compartment with the engine running or with the ignition switch on.

Switching stages:

1st stage:

Ignition ON (for longer than 1sec.) or engine running (actuated by fuel pump relay via booster resistance cable).

2nd stage:

At coolant temperature of approx. 105 °C or engine compartment temperature of approx. 78 °C (OFF at approx. 60 °C).

After-run phase:

Requirement: Engine compartment temperature with ignition OFF > 25 °C

After-run ON:

For 3 minutes at engine compartment temperature > 78 °C. The switch-on condition of > 78 °C is then checked every 10 seconds.

The after-run phase is active for max. 40 minutes."

[DaveCarrera4S]

Reserecting an old thread.  My fan doesn't seem to run at all.  I've been reading about it on various threads.  Seems the fuse for the "always on at low speed" is optional.  I checked and have both fuses and both seem fine.  Not sure why I have an issue.  Headed to the track and want to make sure it is working.