41 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHCabin air temperature sensor fan never stops
Reported repair
Replace ignition switch and it
Reported resolution
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report a fix
1
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported fix
He ended up replacing the ignition switch and it solved the problem.
Leading evidence: 'Replace ignition switch and it' (1 discussions report resolution; 0 report an unsuccessful attempt). Across 1 matching discussions, the most frequently mentioned possible cause is 'power leaked into' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Replace ignition switch and it' (1 discussions). For that action, 1 discussions report a resolution and 0 report an unsuccessful attempt. The most frequently reported fix is 'Replace ignition switch and it', supported by resolution reports in 1 discussions. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that report identifying a cause
1
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause
Since your issue is power leaked into that circuit, it may be worthwhile to check for any parasitic drain when the emgine is off and the alarm is armed.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
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Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed · Original poster
Fuse C7 was still hot, even with the ignition switch disconnected so that got my gears turning.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed · Original poster
I pulled out both of them and clipped the wire at each end and installed a jumper and viola, the temp sensor turns on and off with the key!
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Suggestion
Since your issue is power leaked into that circuit, it may be worthwhile to check for any parasitic drain when the emgine is off and the alarm is armed.
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
I couldn't wait to find out what would happen so after dinner I ran out to the garage and undid my jumper and reconnected the original wire with relay #4 removed.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
power leaked into
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that report identifying a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause
Since your issue is power leaked into that circuit, it may be worthwhile to check for any parasitic drain when the emgine is off and the alarm is armed.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
41 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
1 acknowledgements have no verified action link; they do not establish a repair result.
Outcome without a verified action link
The C7 circuit is still getting power from somewhere.
Hi all, new 996 owner here (2003 cab). I'm loving the car so far but recently noticed that the little cabin air sensor fan on the right side of the dashboard never stops running. I don't mean "runs for a while after I shut off the car", I mean it runs all the time, day and night. I pulled the fan out of the dash and unplugged it to stop it draining the battery. I tried a few searches but was unable to come up with a match.
Any thoughts? Thanks in advance.
Fan pic for reference.
Hmmm...never even heard of that before. Did not know there was a little fan there. It should have a part number stamped on it somewhere. Maybe the fan is fried.
It does...99665324100. I don't know if the problem is localized to the fan itself (there appear to be two sensors on it), or if the HVAC unit is commanding it on. I am clueless how to diagnose it without randomly throwing parts at it.
#17 here? Not sure. Seems the temp sensor and fan are integrated?
http://www.autoatlanta.com/porsche-p...section=809-01
Might want to call them and confirm the year and fit with your VIN. Pretty darn expensive at $385. Saw some on Ebay with Google search.
Logic would dictate to me that whenever the HVAC system is on, the fan would run pulling in cabin air to determine the temp, along with the reading from the outside air temp sensor to differentiate the difference, and thus how much to cycle the AC compressor and run the HVAC system. Does it still run even if you turn off the HVAC system completely? Has to be done with the car running, HVAC not in auto, and lower the fan speed until the HVAC system shuts completely off.
Checked the wiring diagram for you. The power to that fan is supplied by the "Actuation heating" relay (relay #18 in post #9 here
https://rennlist.com/forums/996-foru...l#post13490245
) through fuse D6.
Try swapping the relay with one of relays #19-22 and see if the problem goes away. Perhaps it's a shorted relay. If not that, you need to find out why that relay is activated all the time...likely a bad ignition switch.
Well, you were exactly right about Relay #18 being the power source for the sensor/fan. Unfortunately, swapping relays didn't change the behavior. On a whim, I decided to pop the HVAC unit out of the dash and unplug it and the fan kept running - so I guess the HVAC isn't triggering the fan. Not sure where to go now.
Good, now remove fuse c7 and if the fan stops, your problem is the igniton switch.
Power flows from the battery to the ignition switch (when the key is turned to position I or II), fuse c7 and relay #18 to activate the relay. Nothing to do with the hvac unit at all.
It continues to get interesting. Fuse C7 was blown. I replaced it and it did not blow, but it also did not change the fan behavior. Interestingly, the previous owner had both the combination switch (4 stalks) and the ignition switch replaced less than 500 miles ago.
Good, so we are sure the fan is getting power from the power side of the relay. You swapped the relay with no change so the relay is fine.
So the relay is activated somehow. Per the stock wiring diagram, the relay gets its power from fuse c7, which in turn gets power from the ignition switch. You already said even when fuse c7 was blown, the fan is still running. So seems like it's not a simple problem. Will need lower level troubleshooting with a multimeter.
There was a guy on another forum that was experiencing all kinds of electrical gremlins. He ended up replacing the ignition switch and it solved the problem. I couldn't believe that little part of the ignition shaft would cause so much trouble. Hope you find the solution. You're in good hands with Ahsai.
Dug in a little more this morning. I climbed under the dash and pulled the connector off of the ignition switch and the fan continued running. Fuse C7 was still hot, even with the ignition switch disconnected so that got my gears turning. I reconnected the ignition switch and pulled out fuse C7 and found that one side of it was indeed switched on and off by the ignition switch. However, the other side was always hot! So it appears that something past the fuse is maybe internally failed and is backfeeding power to C7?
Thats what it sounds like to me. Ill dig into my Bentley book and see if i can find any wiring splices in there diagrams later tonight.
if not u may be pulling wire looms apart looking for chaffed wires.
Great. You need the wiring diagram. That c7 circuit is connected to a few systems such as the lamp switch, term XE relay, etc .
PM me with your email if you need the wiring diagram.
Ok, try remove relay #4 and #9, one at a time and see if that changes anything. Then unplug the headlight switch.
All done with key removed from ignition.
I found the 1999/2000 model year diagram online, I think it's probably close. I dug some more and found that pin 86 of relay 18 was always hot, which made sense considering the fault. The more I thought about it, I realized that the fused side of C7 should go directly to pin 86 so the fault HAD to be between the fuse box and the relay box. I pulled out both of them and clipped the wire at each end and installed a jumper and viola, the temp sensor turns on and off with the key! Juding by the complexity of the wiring loom and its sheer size, the jumper may be a permanent fix. I have no desire to unwrap the whole harness looking for a melted or chafed wire.
Temporary jumper wire.
Yeah, that's my concern as well. Everything seems to work OK so far, no warning lights and the AC compressor does engage. I will give a cursory look at the harness to see if I can find anything obviously wrong but in all likelihood, I will locate some matching wire and solder it up and put it all back together.
I really appreciate all of your help on this. You started me down the right path, thank you!
Anytime.
Since your issue is power leaked into that circuit, it may be worthwhile to check for any parasitic drain when the emgine is off and the alarm is armed. Should see no more than 30mA or so after 1hr.
I guess I'm not quite out of the woods yet! Driving around today I started messing with everything electrical I could to see if my "fix" had broken something else. I found that the rear window defogger was not working. A parasitic draw revealed a 250 milliamp draw that was reduced to 25 milliamps when I removed fuse D2 (defrost and mirror heat);
I also noticed that my seat heaters can be turned on with ignition off, which doesn't seem right either but I don't know any better.
I'm gonna go back into it this weekend. Pretty sure relay 4 is also actuated by fuse C7 which must still be shorted.
Should the seat heaters be switched with the ignition?
I have more digging to do! At this point I have relay 4 removed and have a 25 milliamp draw, which I think is fine. Removing relay 4 also disabled the heated seats so they are unintentionally connected! At least now The battery won't die overnight until I can track down the issue with the seat heat/rear defog/mirror heat.
I'll report back when I find out more. Weird that I seem to be the only one to ever experience this.
The problem is that C7 circuit is still shorted so it's powering a few things that should not be powered with the key removed. That's despite the fact you cut out the temp sensor fan. The C7 circuit is still getting power from somewhere.
If you can revert your fix, then remove relay #4 and #9 one at a time, you may be able to isolate the source of the leak.
I will try undoing my fix this weekend and see what happens with that. Another data point - with relay #4 removed, the fog lights and rear driving lights no longer work. Reinstalling #4 restores them, which I think would tend to confirm your theory about #4 being shorted!
The simplest is to undo your fix then remove relay #4, if the temp sensor fan stops and everything else (i.e., lights, heated seats, etc) works and the ONLY side effect is no rear defroster and heated mirrors, then it's very likely you have a bad relay #4 (which has electronics inside to implement the latching function of the defroster switch).
My friend, you're a genius! I couldn't wait to find out what would happen so after dinner I ran out to the garage and undid my jumper and reconnected the original wire with relay #4 removed. Absolutely everything works as it should...the cabin temp fan runs only with the key on, the seat heaters only work with the key on, and the front and rear fogs work correctly. Parasitic draw shows 25 milliamps.
I owe you a beer! What a circuitous route to take to find a bad relay!
It gets weirder. I googled the number of the relay I pulled out of position 4 (99661511901) and found it referred to as a "Trunk entrapment" relay. It was installed in the defrost relay location. The number I found for a correct defrost relay was 99661511700, which just happened to be the part number of the relay in position
5
! I further looked at some photos online and every photo I saw showed 99661511700 in position 4 and 99661511901 in position 5! I took a chance and moved 99661511700 to position 4 and whaddya know, my defroster turns on now. I left 99661511901 at home so position 5 is now empty. So...
1. Can anyone verify that 99661511700 belongs in position 4 and 99661511901 belongs in position 5?
2. What exactly is the "trunk entrapment" relay supposed to do? I cannot find anything that does not work with relay 5 removed, including the remote trunk release on the key.
I guess some ham-fisted mechanic must have inadvertently swapped relay 4 and 5 causing all of this.
OK, here's the full scoop. A "trunk entrapment" relay is exactly what it sounds like. In about 2002, federal law mandated a release handle in the trunk for safety reasons. This relay controls it. So although the yellow handle is literally inches from the latch and one would assume a simple cable would do the job, Porsche knew better and created this electronic apparatus to release the trunk latch. I confirmed this by checking the handle operation with the relay both installed and removed.
So yes, relay 99661511700 (defrost) belongs in position 4 and 99661511901 (trunk entrapment) belongs in position 5. Since the law went into effect in around 2002, that's why earlier cars (and the wiring diagram) show position 5 as empty. I lay the blame for my problem on 2 factors - the mechanic who put the relays in the wrong place and Porsche for putting two totally incompatible relays with identical pinouts right next to each other. Frankly I'm surprised I didn't find more examples of this happening!
Do not switch these relays!
Bad things happen. On the positive side, everything is 100% fixed and it didn't cost me anything. So there's that.
