3.2S keeps blowing fuses.

Mike.Gamble · Jun 4, 2015

I've been offered a '03 S with a few issues.
Basically, she's been neglected a little (and some may say, stay away!) however the garage who are trying to sort her out for the owner (not Porsche specialists) say that apart from the fault which I'll go into in a moment, the car seems quite good.

A few months ago the engine management light came on and the owner kept driving and never bothered having it looked at.
A few weeks later whilst driving the car, it cut out completely, just died and rolled to a stop. No bangs, noises, pools of fluids, just stopped working.

My local garage are a recovery agent and as the owner is fairly local, they recovered it for him. Once back at his garage, the owner asked them to fix the fault. The garage reluctantly agreed and discovered a blown fuse. The fuse was replaced and it blew again.

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The offending fuse is the 25 amp one, on the 4th row of fuses from the bottom on the left hand side.

My local garage couldn't find the root of the problem so it was then taken to OPC to be looked at. As is often the way, the car didn't display any faults while with them and although then ran it up several times, they could find nothing wrong.

After refusing to allow him to have the car back unless it either was trailered back or, had two new rear tyres as they were showing cord (I told you she was neglected!) he collected the car with her new rear tyres and started to drive it back. As could be almost predicted, it got halfway home before completely cutting out again!

The owner once again called the local garage to collect him and against the garages suggestion of returning the car to Porsche in it's non-running state for diagnosis, the owner decided to have it brought back to the garage for them to look at it!

The garage are not to keen to dig deeper as they're of the opinion if Porsche can't find it, what chance to they?

Once again, sometimes after the fuse is replaced the car will run fine for a couple of days but then it will suddenly go and then blow a succession of fuses. The only thing the garage have noticed is that there does seem to be a link with when the fuses blow and when the car is 'jolted' ie going over a speed-bump, pot-hole etc.

My thoughts are, the ignition? For something to happen where the car just stops, 'as if the ignition has been turned off' is that the ignition has turned off. Faulty barrel, broken wire etc?

Any thoughts or similar experiences?

ibaker · Jun 4, 2015

I think the answer will depend on which fuses are blowing. Fuses are a safety device to prevent damage to the items they are connected to. Generally they blow when too much current passes through them as a result of an issue like a short.

Its usually just a matter of tracing back the fault in the effected circuit - until the faulty wiring or component is found.

Alternatively pop it onto PIWIS which will tell you which circuit is causing problems and identify other faults.

Whoever is looking at it needs to establish a plan and then just work through the circuits until they find the cause.

The 4th row doesn't say where it is (from top or bottom?) and row C (4th from bottom)has 4 25 amp fuses.

Mike.Gamble · Jun 4, 2015

ORIGINAL: ibaker

The 4th row doesn't say where it is (from top or bottom?) and row C (4th from bottom)has 4 25 amp fuses.

4th row from the bottom, the 25 amp on the left hand side

Chappelle · Jun 4, 2015

A few websites suggest this is the wrong fuse. See

http://www.renntech.org/forums/topic/33880-2000-boxster-s-fuse-panel-plan/

Okay this is for a 2000 my car but it suggest this fuse should be 30A. Also 4th one in should be 25A but your pic shows it is 30A

Worth investigating thoroughly and it could be as simple as that BUT it could be something more sinister

It could be a short, or water getting into the electrics. Go into it with an open mind, it could take huge numbers of hours of expensive garage time to resolve. Personally I wouldn't touch a neglected car unless it runs and you fully intend to neglect it too and you don't mind taking the risk. Turning a dog into something better will cost more than buying a cared for example in the first place

Fred Hindle · Jun 4, 2015

Row C
From the left.
1 Engine Electronics (25amp)
2 Ignition, fuel injection, oxygen sensor, heating (30amp)
3 Central locking (15amp)
4 Fuel pump (25amp)

http://rennlist.com/forums/996-forum/583705-help-finding-c4s-fuse-plan.html

Cheers,

Richard_Hamilton · Jun 4, 2015

If you are counting the spare fuses in the bottom row, then it seems like it is fuse C1, which is for the engine electronics (DME). I have heard of a couple of cases where this fuse blows due to the wire to one of the Variocam solenoids chafing through and shorting to ground. If you could confirm it is C1, then there is obviously some short to ground in the engine loom, or it could possibly be within the DME itself.

This is for a 996, but the fuse box is the same, and the assignments are mostly the same.

https://www.porscheclubgb.com/legacy/clientftp/Register/996/tec_996_fuses.pdf

Geoff_Fields · Jun 4, 2015

Fuse C1 feeds MFI relay contact, which then provides power to quite a few engine related components. For me the clue is it will run for a while. So what might cut in after the engine has been running for a while? My guess would be the engine bay cooling fan. Could try pulling the connector from that.

Mike.Gamble · Jun 4, 2015

ORIGINAL: Madelvic

It could be a short, or water getting into the electrics.

I did consider water and put my hand under the passenger side carpet to see if it was damp due to the ducks bill drain being blocked and soaking the module under the passenger seat but it was bone dry.

For some reason, I keep convincing myself it's the ignition!

Mike.Gamble · Jun 4, 2015

ORIGINAL: Richard Hamilton

If you are counting the spare fuses in the bottom row, then it seems like it is fuse C1, which is for the engine electronics (DME). I have heard of a couple of cases where this fuse blows due to the wire to one of the Variocam solenoids chafing through and shorting to ground. If you could confirm it is C1, then there is obviously some short to ground in the engine loom, or it could possibly be within the DME itself.

This is for a 996, but the fuse box is the same, and the assignments are mostly the same.

https://www.porscheclubgb.com/legacy/clientftp/Register/996/tec_996_fuses.pdf

Yes, I was counting the lower row of spare fuses. I'd forgotten they were spare!!

Glyn · Jun 5, 2015

On the inside of the plastic fuse cover you should have a folded up piece of paper with each fuse designated and should be able to identify which circuit is causing the issue.
Have you connected an OBD diagnostic reader to the car? any codes?
I don't see where you are in the country but you could give Russ a call at Revolution Porsche - (Brighouse) This guy and his team are fantastic and they are genuine nice honest people to do business with, Russ will recover the car if needs be.

When you say it blows the fuse, Is there a pattern to it, will it tick over and get to normal temp before cutting out, do you need to be revving above a certain level, using any ancillary equipment. You need to note everything that is happening at the time the fuse blows in order to have a chance at identifying where the short is likely to be.

Check all the cables in the engine bay for chafing.
Of course, the ignition switch is a well known weak point but unless you are fiddling with it when the car is running its unlikely to be a fault with that, Your fault sounds like something that is either activated with temperature or revs, or perhaps driving on a rough road.

Good luck with your search

Boxstercol · Jun 6, 2015

The car's not the problem, the irresponsible owner is.

Running a car like this, or any car for that matter, with defective tyres is a disgrace. It could kill someone & as far as I'm concerned the OPC did the right thing.

Richard_Hamilton · Jun 6, 2015

ORIGINAL: Geoff997

Fuse C1 feeds MFI relay contact, which then provides power to quite a few engine related components. For me the clue is it will run for a while. So what might cut in after the engine has been running for a while? My guess would be the engine bay cooling fan. Could try pulling the connector from that.

That has its own separate fuse Geoff.

Geoff_Fields · Jun 6, 2015

Yes Richard, I was aware of that. I don't have a circuit diagram but I assumed that the engine compartment fan, via it's 15A fuse along with other devices like fuel pump, via it's xA fuse all together are getting their power from dfi relay? So maybe together were drawing too much current some of the time. Hence my guess of fan, which cuts in after a while. Anyway I bow to your greater knowledge.