Boxster No power to anything on fuse circuit C3

Hi.
I have a 1998 Boxster which I just replaced the electrical portion of the ignition switch on. After replacing the ignition piece everything on the "C3" fuse circuit (power windows, interior lights, locks and alarm) no longer work. I checked the "C3" fuse on both sides with a test light and there is power on both sides. I also removed the fuse and put a jumper from one side to the other and still nothing to any of the accessories on that circuit. I also reinstalled the original ignition switch (issue was key removal) and still no power to those accessories on that circuit.

I've checked for anything that might have been distributed and can not find anything.

Any idea what to check next? Again it's only the accessories on that "C3" circuit

Thank you
Jim

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offroadjim
Hi.
I have a 1998 Boxster which I just replaced the electrical portion of the ignition switch on. After replacing the ignition piece everything on the "C3" fuse circuit (power windows, interior lights, locks and alarm) no longer work. I checked the "C3" fuse on both sides with a test light and there is power on both sides. I also removed the fuse and put a jumper from one side to the other and still nothing to any of the accessories on that circuit. I also reinstalled the original ignition switch (issue was key removal) and still no power to those accessories on that circuit.

I've checked for anything that might have been distributed and can not find anything.

Any idea what to check next? Again it's only the accessories on that "C3" circuit

Thank you
Jim

Fuse C3 controls the power windows circuit and the alarm control module. Whenever "alarm control module" is mentioned I have to raise the possibility of water in the cabin. The alarm control module is under the passenger seat on the floor of the cabin. Any water in the cabin via it blocked body water drains (front or rear), leaking top (or a top left open in the rain), or even leaking door seals (membranes) will collect at the lowest point and probably if not submerge the module get it wet.

To be safe I think you need to confirm the cabin floor is dry and the alarm module shows no signs of any water damage. You will probably have to remove the passenger seat to get full access to this area. My reference (Bentley Boxster manual) shows a 15amp fuse at the alarm module too. So while you are there look for a fuse and be sure it is good.

Check along the door bottoms. If there is any dampness water is getting from the wet side of the door to the dry side and water on the dry side even if it doesn't make it to the cabin floor and the security module under the passenger seat can cause electrical gremlins to appear.

I recently went through a bout of wet door bottoms with my Boxster. Fortunately I caught this before any water got past the door bottom carpet into the cabin. My advice is if one or both door bottoms are damp/wet to replace the door membranes with new ones rather than trying to reglue/seal or repair the old membranes. My experience is the repair will not hold up for long.

I pulled the seats out today and the alarm wound up being under the drivers seat and the 15 fuse in it was good. I can't seem to locate any type of diagram to show me where the line from the fuse box goes to next and how it powers all the individual accessories

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offroadjim
I pulled the seats out today and the alarm wound up being under the drivers seat and the 15 fuse in it was good. I can't seem to locate any type of diagram to show me where the line from the fuse box goes to next and how it powers all the individual accessories

The Bentley Porsche Boxster manual has a wiring diagram for the '98 (and newer models).

Fuse C3 has two wires both run over to the "CU ALARM". One line connects to the "EXTERNAL CONSUMER" pin the other line connects to a "FUNCTIONS INDICATOR" (and this in turn connects to a "FUNCTIONS INDICATOR" pin of the CU ALARM and the "CENTRAL LOCKING BUTTON".

There are wires from the CENTRAL LOCKING BUTTON. These go to 'DOOR LOCKED DISPLAY" pin, "BUTTON CLOSE" and "BUTTON OPEN" pins, A line leaves this and runs over to the "REAR WINDOW HEATER BUTTON".

Thank you! I pulled the seat back out and there is power at the connector going into the box but if I use a test light (assuming it's 12v) at the 15amp fuse on the box I get nothing. The box definitely has a smell to it not that that is an indicator of anything

So does that mean that the power goes from the fuse box to the alarm under the seat and the. To the locks, windows, etc?

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offroadjim
So does that mean that the power goes from the fuse box to the alarm under the seat and the. To the locks, windows, etc?

I'm no electrical circuit whiz but it would appear the power flow direction is from the fuse box to the CU ALARM. The power for the locks/windows I think gets to where it needs to be by another circuit. In this case these lines do not carry power to control the door locks/windows only power that signals their state.

Would there be a way to temporarily wire it so that the windows at least get power?

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offroadjim
Would there be a way to temporarily wire it so that the windows at least get power?

I have no idea. I'm not qualified to advise you regarding attempting a temporary electrical wiring bypass.

To state the obvious there is some kind of electrical problem I guess -- I have not re-read the previous posts -- that is not due to a bad fuse or even a relay. To try to jury rig some emergency wiring patch/modification to get around this is risky.

My Boxster has had a few "electrical" problems such as windows not dropping when they should or going up when they shouldn't, door locks locking on their own, and the horn sounding a warning that something is ajar when I lock the car when nothing in fact is ajar. In these cases I have taken the car in and let a Porsche tech make the diagnosis. The process was rather quick as the car's got a rather sophisticated security control system that can do some self-diagnosis and the tech can obtain this info and knows what it all means.

... I would install the old ignition switch just as a test.
If the windows work, the you know the new switch is bad.
There are a lot of cheap knockoffs that may not work.
I have seen several in my Boxstering years.
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)

---

Racecar spelled backwards is Racecar

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

"Being second is to be the first of the ones who lose" ... Ayrton Senna

Hi
I tried switching back to the original ignition switch several times because it would seem that the last thing touched would have something to do with it but it did not work with the original one either

Last night I changed the passenger side brake light as it was out and when I went to open the door to get in the car the driver window decided it would go down all the way. Ughhh as I still can't raise or lower them. So now being that it's 30* here I need to get the window to go back up. Any ideas how I can get it to go back up now?

Quote
offroadjim
Hi
I tried switching back to the original ignition switch several times because it would seem that the last thing touched would have something to do with it but it did not work with the original one either

Last night I changed the passenger side brake light as it was out and when I went to open the door to get in the car the driver window decided it would go down all the way. Ughhh as I still can't raise or lower them. So now being that it's 30* here I need to get the window to go back up. Any ideas how I can get it to go back up now?

AFAIK there is no emergency window raise feature/procedure.

My experience has been when the windows act erratically upon opening the doors it has been a door lock controller. The door lock controller, a rather large plastic/aluminum box, has some electronics smarts as well as some plaiin old mechanical/electrical hardware inside.

However, the window lowering all the way down was not a symptom. The window not dropping when the door was opened or worse dropping then after a brief bit of time going back up again *after* the door was opened was what I remember.

The cabin floor is dry. If the door bottoms are dry I have no idea, other than possibly the battery if it is (too) low...

My advice would be to get the car to a qualified shop for a professional Porsche tech's diagnosis. As I think I mentioned in a previous post the car's security system controller has some abilty to detect a problem and when queried using the Porsche diagnostics computer (or perhaps a Durametric) can provide error codes that can help someone with the right info make a diagnosis.

As an aside when I first bought my Boxster I bought a Porsche outside cover for it just to have in case the top developed a leak or a window leaked, or something leaked. You might consider picking up a suitable outside cover to use to cover the car while you are dealing with the problems. It won't keep the car secure but with the cover on the fact one or both windows are down may not be that obvious. At least the cover would keep out the elements.