Fuse keeps blowing

[RS4Cab]

A week ago I noticed my radar detector stopped working so I checked fuses, Now I had hardwired and it's impossible to see which wire went to what so had no idea what wire I broke in on. So I checked fuses and found the blown one was "Pump for Brake Booster" so changed and radar worked again but it blew again pretty quickly. So decided I better take the detector off that wire. Remove the suit case connector and wrapped where it was broken into with electrical tape. But fuse keeps blowing, but I have been driving with it blown and no problems with brakes? Also no lights coming on in dash warning of a problem. Figure I probably need "Pump for Brake Booster" working. will bring into dealer to see whats going on.

[harrison]

I would feel safer tapping into the auxilary/cig. lighter power line/source. Your problem is different for sure. Hope it gets worked out ASAP.

[RS4Cab]

I would feel safer tapping into the auxilary/cig. lighter power line/source. Your problem is different for sure. Hope it gets worked out ASAP.

Thats what I wanted to tap into but could not figure which wire that was, but I am there now. I went old school and cut the connector off the wire, stripped some off the end and put in front of fuse prong and pushed in. Figure detector has inline fuse so should be okay

[M3R8]

Pure guesswork here, but it's very much possible this pump is only put into action when serious boost is needed on the breaks, or maybe over a certain driving speed, and possibly a fault in it would only be detected when that happens, or when it's actually put into use.

Who knows, maybe the pump is actually shorting and is causing the fuse to blow.

Glad I tapped the cig lighter in my install... I didn't want to tap anything at or near the fuse box, so I tapped the cig lighter directly with a short cable that I ran from it back to the fuse box where I have my radar detector/laser jammer boxes stored.

Good luck!

[Yspokes]

Please keep in mind that you should never tap into a fuse that supplies a system with a critical function. Use a spare (empty) circuit in the fuse box, or the cig lighter line, as the fuse for the cig lighter has a much higher amperage rating and likely will not blow. I would take the radar OFF of the brake pump booster circuit, and keep checking that fuse to make sure it still is not blown. If it continues to blow with the radar disconnected, then there is an issue with the booster pump or its associated wiring.

Also, don't assume the detector has an in-line fuse on it unless you know for sure. In the case that the detector has a fault it is likely that the in-line fuse will blow first, as it likely has a smaller amperage rating. PLEASE check that this is in fact, correct.

[rmicroys]

Just on the description is sounds like a vacuum pump to supply additional vacuum for the brake booster. When you're on the track at WOT all the time, the engine has very little time to generate vacuum. Not unheard of. So as long as you stay off the racetrack and the mountain switchbacks, then you should be okay. I'd still say get it fixed soon. Just be aware that all of a sudden you may find your brakes go really firm on you and you'll need a lot of leg pressure to stop if that happens.

I know, I run my racecar without a vacuum booster and it's quite the workout, particularly during 3hr enduros.

[RS4Cab]

Please keep in mind that you should never tap into a fuse that supplies a system with a critical function. Use a spare (empty) circuit in the fuse box, or the cig lighter line, as the fuse for the cig lighter has a much higher amperage rating and likely will not blow. I would take the radar OFF of the brake pump booster circuit, and keep checking that fuse to make sure it still is not blown. If it continues to blow with the radar disconnected, then there is an issue with the booster pump or its associated wiring.

Also, don't assume the detector has an in-line fuse on it unless you know for sure. In the case that the detector has a fault it is likely that the in-line fuse will blow first, as it likely has a smaller amperage rating. PLEASE check that this is in fact, correct.

I now have it off the brake bumper booster line, Because I could not determine which wire was for cig lighter I just bared wire and stuck it into cig fuse. The hardwired setup does have an inline fuse so not worried about detector. I made sure to tape up good where I broke into brake booster wire so thinking I might have some other problem with brake pump. Going to bring in next week and wondering if I should take the tape off that wire and just play dumb so they don't think I did anything wrong and not have it covered by warranty.

[Rit2]

The operation of that booster pump is important for the ABS. It provides pressurized brake fluid during times when there's insufficient pressure to manage the ABS. I'm surprised that the system design has not taken into account the circuit failure, even though its operation is of a supplemental basis. This system is more important when it's on a DFI engine high performance cars (unless the R8 uses an electro-hydraulic brake system design, which I'm yet to check). It appears that the failure this supplemental feature to operate will only to be discovered during critical moments.

Thanks for sharing this crucial information.