LSR

Yes. The cause was a flakey DME relay. When I removed it and shook it, it rattled. Relays aren’t supposed to rattle. So on a hunch, I smacked it against my workbench a few times and the rattle went away. I reinstalled it and the car’s been perfect ever since. So the cure literally was “kick it” and see if that fixes things. Oddly, it did. If the problem reoccurs I will buy and install a new DME relay.

barncobob

dealer would charge $500 to kick it

LSR

LOL! Not even close. My dealer misdiagnosed the problem for a cost of over $400 in diagnostic expenses, claiming the problem was due to a bad alternator and wanting $2200 more to replace it. When I balked and complained to Porsche NA, after having diagnosed and fixed the problem on my own, I ended up receiving a $500 “Loyalty Voucher” from Porsche NA for my troubles.

adub87

Hey LSR, I am having a similar issue of my front fans staying on after I turn off ignition. Was gonna go ahead and replace DME relay as you suggest. Any information you can share on that process? Thanks!

LSR

If you have a 991.1 non-Turbo, then the fans should not receive power with the engine off. That’s because the fans receive their power through a circuit that runs through the DME relay, which is supposed to be de-energized when the engine is off. So, if your front fans continue to operate with the engine switched off the most likely cause is a stuck DME relay. A new relay costs around $54 last time I checked (which is a while ago). Just unplug the old relay and pop in a new one (or, if the old one is rattling, give it a couple of whacks and see if that fixes it like I fixed mine). If you have a Turbo model, I do not know if it’s front fans receive power also through the DME relay as that car has a different circuit diagram and I never traced it. Getting to the relay is simple - put the rear seat backs down and pull up the foam-backed carpet that’s covering the wall behind the seat backs to expose the relay and fuse block.

barncobob

now U can buy one of their T shirts in the parts dept.

adub87

thanks! I have a 13 C4S so these directions should work. I actually just found another thread you started (https://rennlist.com/forums/991/1199...n-991-1-a.html) where you posted image of annotated relay and fuse box… really helpful. I ordered the relay based on part number you included there (955-615-025-10).

one more (maybe stupid) question: in the event that fans don’t turn off, can I just pull DME relay? The part won’t arrive for a few weeks and I’m trying to avoid a situation in which fans drain battery (luckily, yesterday they turned off on their own, but not sure I’ll be that lucky again…)

LSR

There are no stupid questions when it comes to these cars. :-) My fans also sometimes would turn off on their own. But sometimes not. I surmise my car's DME relay contact got stuck somehow in its N.C. position (keeping the fans energized) and sometimes would go back to its N.O. position (turning the fans off). Yes - you can pull the relay to stop the fans, keeping in mind this will also stop your car. If you do pull the relay, shake it near your ear to hear if it's rattling. If it is, give it a few whacks on a counter top (not on the pins - on the top or sides) and shake/listen to it again. If the relay no longer rattles, plug it back in and see if that solves your problem. Good luck.

downfarce

I am having an issue with my 2013 C4S where just my front right radiator fan was turning on whenever I opened or shut my door, irrespective of whether the engine was warm or even running. I tried replacing the DME relay, unfortunately this does not resolve the issue. Wondering if it could be an issue just with the front right radiator fan relay and where that might be located?

LSR

Short answer: Yes, it could be (likely is, IMO), the fan relay. I believe it's located under the driver's side dash and is a pain to access. I've never tried to find it, though, so others may know better how to get to it.

Longer answer: If only one fan is operating when the engine is switched off, then the problem would likely not be the DME relay. The DME relay is the likely culprit if both front radiator fans continue operating when the engine is switched off. But if only one fan operates with the engine switched off, chances are that fan's corresponding fan relay is the problem. This can best be understood from the wiring circuit for the fans, which I describe below.

The wiring diagram for a 2013 991.1 non-turbo (service manual, Fig. 2 - Cooling Fan Circuit, W/O Turbo) shows each front radiator fan has a fan relay the coil of which receives power from the DME relay when it is actuated. The DME relay is actuated when you switch the ignition on. So if the engine is switched off and everything is operating normally, the DME relay will be de-energized and its relay contacts will be opened, which removes power from both fan relay coils, which in turn will cause both fan relays' contacts to open to remove power from both fans. Thus, both front radiator fans should immediately stop running when the engine is switched off.

If the DME relay is faulty by failing to open its contacts when you switch off the engine, both fan relays will continue to receive power from the DME relay's contacts. This, in turn, will energize both fan relays to connect both front fans to power even though the engine is off. So, both fans can run if the DME relay gets stuck "on."

But a different cause is likely when only one fan continues to run when the engine is switched off. When a properly operating DME relay is off (engine is off), the fan relays will be de-energized and power should be removed from both fans. But if one of the fan relay's contacts get stuck and fail to open, power will continue to be provided to the relay's corresponding fan. This will result in one fan receiving power (when it shouldn't) while the other properly remains unpowered. The result will be only one fan will operate when the engine is off. This is what is likely happening with your car.

A quick test is to confirm it's likely the fan relay is to pull out the DME relay entirely. This will remove any possibility of power being provided to both fan relay coils (assuming you don't have a short circuit somewhere, which is not likely). If a front radiator fan continues to operate even with the DME relay removed, I'd take that as a confirmation it's likely that fan's relay staying stuck closed that's to blame.

You may be wondering why a fan with a stuck fan relay sometimes stops and starts on its own when you open a door or whatever. The reason seems to be because even though a fan may be receiving power from its stuck fan relay, that's actually not what causes the fan to turn on. The fan motors operate in response to temperature sensor signals. When the engine is off, the temperature sensor signals should be off so the fans should be off even if a fan relay is stuck. But the fans have an emergency mode. The SIT manual for the car says: "The fan motors are operated in emergency mode (maximum speed) if the drive CAN bus is faulty or a fan control unit is not receiving any signal from the DME control unit. Measuring the current consumption not only provides a way of detecting short circuits, but also stiff/mechanically blocked fan motors." I underscored the sentence that I think is the blame - with a stuck fan relay providing power to its fan, if the engine is off the DME unit will be off and no longer sending signals on the CAN bus. The still-powered fan will think it's lost communication with the engine and will treat this as an emergency coolant situation, and will turn on as hard as it can.

So, where is the fan relay that you want to replace? As stated at the outset, the fan relays are in relay "support 1," which is also where the fuel pump relay is. I believe that is under the driver's side of the dash, and I have heard it's a pain to access. Having never tried to access it, I cannot confirm either where it's located or how difficult it is to reach.

Good luck - and please post if you determine the actual problem and solution.

downfarce

LSR, thank you for your thorough and well thought out response, it is much appreciated. As you suggested, I did pull the DME relay and opened/closed the door multiple times without the rad fan switching on. Once I plugged the DME relay back in, the rad fan started its intermittent behaviour again. Any thoughts as to what this might indicate?

downfarce

LSR, thank you for your thorough and well thought out response, it is much appreciated. As you suggested, I did pull the DME relay and opened/closed the door multiple times without the rad fan switching on. Once I plugged the DME relay back in, the rad fan started its intermittent behaviour again. Any thoughts as to what this might indicate?

LSR

I’ll look at the circuit diagrams again, because the DME relay may be affecting other circuits. But to confirm, because different circuit diagrams could be involved, you have a 2013 4S 991.1 non-turbo coupe, right? Does it have Bose or Burmeister? How many miles on the car? How old is the battery? You should by now be on at least your second battery with a 2013. Also, when my front radiator fans started to have a life of their own, I found it impossible to figure out what triggered them. Sometimes they started within a minute after the car was shut off. Other times they started if I opened the drivers door but not the passenger door. Sometimes the fans stayed off and never came on when the car was shut down, even overnight. Other times I couldn’t get them to turn off. And still other times the fans turned off, and in the middle of the night they started up. It made no sense as to when or why they were triggered. So, here’s what I suggest. Pull the DME relay and leave it out, and give it some time. Give it a couple hours, days even. Play with it. See if you can get the fan to operate without that DME relay in. Or, if you want, just replace the fan relay (assuming you can access it) and see if that solves the problem.

LSR

Your situation is a head-scratcher.

In a normally functioning 991.1, when the ignition is off the DME should not be energized and its contacts should be open. This means no power should be sent to the fan relay coils and the contacts of both fan relays also should be open. The result should be that no power should be sent to either of the two 12v terminals of either radiator fan (one terminal receives +12v from the DME relay's closed contacts and the other terminal receives +12v power from the fan relay's closed contacts). This means if the DME relay is operating normally, the fan relays should be de-energized irrespective of whether the DME relay is plugged in or not.

But you say the right rad fan (only) turns on when the engine is off and the DME relay is installed, but the fan doesn't run when the DME relay is pulled. The former is not normal, and the question is: what could be causing only the right fan to run and only when the DME relay is plugged in? Again, if the DME relay was sticking "on" when the engine is off you'd expect both fans to run. But that's not what's happening with your car. Only one fan runs.

It's possible there may be something wrong with the DME itself. Hope not, because that's expensive to replace and I believe it needs to be programmed to your car. So before going there, I'd try to narrow down the possibilities.

I'd first try to isolate the DME relay because this is easy to do. To do that, pull Fuse #1 (it's 10A). It's located in the same fuse/relay bracket where the DME relay is installed (behind the rear seat back). Fuse #1 sends 12v power from the DME relay's closed contacts (when the ignition is on) to terminal #30 of each fan and also to the coil (terminal #4) of each fan relay. So if you pull Fuse #1, whether or not the DME relay is installed or the ignition is on or off, the assumption is the fans should not operate. If a fan does operate with the fuse pulled, that suggests the fan is getting power from someplace else when it shouldn't be and that'll be an important clue. Another easy test to try is measuring the voltages at Fuse #1 under a variety of conditions. With Fuse #1 pulled and the DME relay pulled, test the voltage at each end of the Fuse #1 socket with the ignition off and again with the ignition on (the engine doesn't have to be running). It appears from the circuit diagram the voltages at both ends should be at 0v with ignition on or off. Now, put the DME relay back in (but the fuse is still pulled) and repeat the voltage measurements at the fuse socket. The voltage at Fuse 1 socket terminal 2 should still be at 0v whether the ignition is on or off, but the other terminal should be at 12v with the ignition on and 0v with ignition off.

I'm curious to know what the tests show. If the DME is to blame, the car's symptoms might be explained by a malfunctioning DME that is actuating the DME relay even when the ignition is off (via DME terminal 30, which controls the coil of the DME relay) and possibly also sending a fan control signal (a PWM signal) to the right fan. It would be nice to try to eliminate other possible causes before landing on the expensive one. If the DME is to blame, it's possible the car might post some error codes. If you have an OBD2 reader, you might want to check that.

downfarce

Will try your suggestions over the next few days and report back. Battery is 5 yrs old, might also try to replace it and see if this makes any difference as I have heard about battery related electrical gremlins as well. Unfortunately, this issue has really soured my first year of porsche ownership. However, this forum and folks like yourself are such a valuable resource.