1999 Boxster C3 fuse keeps blowing

I'm having a problem with the C3 fuse that keeps blowing. I replaced the CLU box and am still having the same problem, when the box is unplugged the fuse doesn't blow. I'm guessing there's a short somewhere but I have no idea where, I guess it could be one of the micro switches. Any help is appreciated, this is really frustrating. I read on another forum someone having the same problem but he never mentioned if he resolved it. I'm not sure if he's still active on that forum, his post was about a year old. I sent him a private message but never heard back from him.



Edited 1 time(s). Last edit at 08/12/2015 09:36AM by joecal. (view changes)

is connected to: Central alarm/locking, inside lights, power windows.

I would disconnect the latter two one at a time and see if the problem stops happening. You have to look at a wiring diagram to see where the best disconnection point is. Once you know which circuit it is then you can dig into that circuit.

… "when the box is unplugged, the fuse doesn't blow".
That narrows it down to the CLU.
Happy Boxstering,
Pedro

Pedro Bonilla
1998 Boxster 986 - 311,000+ miles: [www.PedrosGarage.com]
PCA National Club Racing Scrutineer - PCA National HPDE Instructor - PCA Technical Committee (Boxster/Cayman)

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Racecar spelled backwards is Racecar

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"If you wait, all that happens is that you get older"... Mario Andretti

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Both the inside lights (terminal II/11) and the windows (terminal I/18) are connected to the CLU so unplugging the CLU may just disconnect the bad circuit.

Thanks for the replies, sorry I haven't been on here in a few days. The fuse isn't blowing anymore after I installed a 30 amp fuse in the C3 socket and then replaced it with the correct 15 amp fuse. I know that was a dumb thing to do but I read a post where someone said a Porsche tech did that to his car and it solved the problem, his car was having the same issue as mine. The only problem now is my windows won't go up, they went down but now they're stuck down.

Check fuses B6 and D1.

If those are good, put the key in the driver's door, turn it counter-clockwise, and hold it and see if the window goes up.

Thanks for the suggestion, both fuses are good and I tried turning the key counter-clockwise and holding it and nothing happened. I pulled the door handle out a little like I was going to open the door and the window moves a little on the drivers side, but now I don't hear the micro-switch working and the windows not moving. I kept pulling and releasing the handle on the passenger side door and the window came up about half way. I put it down with using the switch but it wouldn't go back up, and now the passenger side comes up using the window switch but only about an inch, but it does go up and down but like I said only an inch or so. The drivers side is not doing anything, it seems I'm getting closer though to a solution. The motors seem to be working when they do. Thanks again and if you have any more suggestions let me know, I'm at a loss. I may have to pull off the door panel as a last resort.



Edited 1 time(s). Last edit at 08/22/2015 11:58AM by joecal. (view changes)

You sure the floor of the cabin is dry?

Actually if there is a water problem in this case given the behavior is limited to the doors and windows the water may be in one or both doors. Give the doors a good shake listening for any water sounds. Check along the bottom of both doors for any signs of dampness.

You might have to remove both door panels to really check for water sign.

Be sure you treat the door air bags with respect. Obtain the radio code. Turn off the ignition. Remove the key. Disconnect the battery. Wait some time or press on the brake pedal to remove any residual electricity from the car's electrical system. Don't hug the air bag and be careful putting down and picking it up.

It doesn't have to be water. It could be one of the door lock assemblies/controllers. If I had to guess I'd guess the passenger side? This gizmo is pretty sophisticated and when the one in my 2002 Boxster went off window and door lock anomalies appeared. With the proper diagnostic computer the security system controller can be queried for any error codes and this goes a long way towards identifying the source of the problem. Otherwise, you can throw some pretty expensive parts at the behavior.

Thanks to both of you, the floor is dry, I had the immobilizer repaired, it did look like there was water damage sometime in the past, I hope I didn't damage it. The car was sitting outside for a few months before I bought it so some water probably did get under the seat and possibly in the doors. I did notice the rear drains were clogged and I cleaned those out. I guess I will have to pull off the door panel and see if I can spot the problem.
Thanks again for all the help.



Edited 2 time(s). Last edit at 08/22/2015 04:56PM by joecal. (view changes)

You have a bent window regulator. When it was partially bent, it required more current to move than normal so that would cause the fuse to occasionally blow. Now it has completely jammed.

I would take the inner cover off the door and take a look.

Hello again, just an up date on the windows. They are both working, it must have been the micro-switch if there is one back there for the convertible top. I raised and lowered the top and now both windows are working. I don't now why but I locked the car with the key and kept the key turned clockwise and pressed and held the button on the key fob and the passenger window went up. I was hopeful then that I didn't damage anything inside the door. I thought let me raise and lower the top and they started working! Thanks again for all your insight and help, you guys are Great!!!! The key fob doesn't unlock or lock the doors but I can live with that, it was like that when I bought the car. I guess I didn't damage the immobilizer fortunately, I probably wasted my money on getting that repaired but the shop said it did have an unrepairable board that he replaced.



Edited 2 time(s). Last edit at 08/22/2015 06:54PM by joecal. (view changes)

None of the convertible top microswitches causes the windows to not function at all. And all of them can be overridden by putting the key in the outer door lock.

That's strange then, I'm not sure what cured it then but I'm just glad they're working and hopefully stay that way!