Climbed in to the C4 yesterday morning to drive to work.
Started the engine, slotted reverse gear and started pulling out of the garage when I noticed that the brake-pedal was rock hard and by the time you expect the hydralic pressure to be ok, that dreaded warning signal started.

I didn't have time to do any troubleshooting at that time so I had to take the train to work, and I possitively hate that!

So finally at work I got time to do some rennlist searching and found several threads which pointed out fuse # 15 as a suspect.

When I got home I opened the front lid, checked the fuses and voila! fuse # 15 was broken, so off the the gas station and by a 40amp fuse.
I spare fuses from 5 to 30 amp but ofcourse if anything breaks it has to be something of which you don't carry a spare...

Replaced the fuse, started the engine, after 30 secs the warning lights disapperad and the brakepedal-feel was back to normal.

Anyway total cost to fix the problem, 1/2 € or about 60 cent...

So a big thank you guys!

...and of course Adrians book have been of great help...

 

I could be wrong - and the C4 is at home, so can't check - but I don't remember any of my fuses being 40A. Isn't this too high?

 

I normally find Rennlist costs me money with all the suggested "upgrades"....!

 

Nope - definitely 40A - hydraulic booster pump fuse 15

 

Yes, that's where the money I saved will be spent.... on upgrades!

 

I guess the question now is why did the fuse blow in the first place?

 

It's the first fuse I've replaced in the car after five years of ownership and I've been on two trackdays in the last month so the brakes have been working pretty hard.

I agree that blown fuses are often signs that there's something wrong but with any luck, maybe it just detoriate with age?

 

I guess it's possible to be just age...

At any rate, thanks for the tip incase any of us have the same thing happen!

 

I agree fuses can degrade with age. If the new fuse holds, don't worry be happy. If you keep blowing the same fuse...

 

I agree with Millemiglia, I did my front brake pads this evening and finished both fronts in under 1 hr having read many threads here........ now for the rear pads..............

Thank you all Rennlisters once again!

 

Hiya Springer3
"I agree fuses can degrade with age."
I'm not understanding how a fuse could degrade with age ?
Its a strip of metal that melts at an amperage .

 

I am not an engineer so can't explain the science behind it but if you do a Google search on "fuse, degredation age" or something similar, there are many references to age adversely affecting fuses and lowering their rating.

Marc

 

Correct... the only thing is that if the contacts are dirty/corroded they tend to create higher resistance in the circuit and that could translate into a blown fuse...

But that is rare...

I agree with Indycam... need to look further to see what was the cause of the fuse blowing...

I would check the Pressure Sensor (US$247.55 - Part # 964-606-904-00) and Relay (US$33.81 Part # 964-615-135-00)...

 

Hiya Wachuko
"the only thing is that if the contacts are dirty/corroded they tend to create higher resistance"
higher resistance = lower amperage .

I really don't think its the pressure sensor , I don't think the fuse thats blowing goes to the pressure sensor . The fuse is for the motor . The relay is the power switch for the motor and the pressure sensor runs the relay ?
If the relay was shorting out internally , then the amps would jump up and blow the fuse .
I've never seen a relay short out internal , but anything could happen I guess .

Great photo !

 

"Fuses also have a tendency to wear out over time due to fuse element deterioration, which causes mysterious fuse failures. Fuse element deterioration occurs when the metal link receives chemical and physical stresses due to repeated short duration electrical overloads that are not serious enough to cause the link to actually melt."

"A less known but still troublesome characteristic is fuse element deterioration, caused by chemical and physical stresses produced in the fuse element during repeated short duration overloads. For example, motor starting produces a short current inrush followed by low running current conditions. The inrush current, usually higher than the fuse rating, is not present long enough to blow a correctly applied fuse However, deterioration of the element, resulting from repeated motor starting, often causes mysterious fuse failures."

....and so on.

Marc
p.s. I don't disagree that a fuse that repeatedly blows deserves investigation, but if replacing one old fuse with a new one fixes the problem then I'd look no further.