Sal 965

I was planning to be out with the 964 crowd today in Wales, UK for some great driving on great roads.

However, on the way there, about 2 miles before the meeting point, the brake pressure warning light came on and the beeper started to sound but, i still had good braking. We arrived, chatted for 30 mins and got back in the car. The warning light was on but no beeping and still good brakes. After about 10 miles though we started on some twisty roads with undulations when, as i went for the brakes, the pedal was stiff and right at the top of the travel.

Well, that was the end of that. I managed to get the car home and started on the books and searches.

I have checked there are no leaks near the booster and that fuse 15 isn't blown so i'm hoping it is going to be relay R51.

My R51 has a 964 code to it but i wondered if there was a VW/Audi/cheaper/easier to obtain alternative relay parts that would fit? Is there also any way to check that the relay is or is not working before buying another?

Also could anybody suggest what, if not the R51, could be wrong with the braking system to cause this. The car has been off the road for four weeks or so and the wheels have been off in that time but i've not been near the brakes.

Any help as usual would be appreciated.

garrett376

If it's not your fuse, not your relay, then I'd look at the pressure switch on the pump to be the next in line to be faulty.

Sten

Steve,
Can you hear the pump running? Is it the same as the C4 964? I have all the circuits if you need more help, plus I have my 'spare' pump and switch.

Sal 965

Is there a way of bypassing the relay - i've heard stories of bypassing the DME on n/a cars using paper clips. Would this work to get the pump running?

garrett376

Yes you could bypass it... or just connect it to a 12V power source. I don't have the wiring diagrams accessible but you can bypass the relay with clips, or by providing a 12V source directly to the motor itself.

Wachuko

Had this happen to me a long time ago... Here you go:

Best source for PDAS pump and/or pressure switch?

The problem was solved by: Pressure Sensor replaced(US$247.55 - Part # 964-606-904-00), Relay replaced (US$33.81 Part # 964-615-135-00), Rubber O-Ring replaced(US$4.99 Part # 999-707-094-40). Labor US$147.90 Minus PCA discount.

Try Sunset Imports/Porsche for the parts (did not know about them at the time)... they should have a good price. - http://www.sunsetporsche.com/

UK... need to look for a local source I guess, for the parts... let's know how things go...

garrett376

Terminal 3 jumpered to Terminal 5 at relay R51 will activate 12V to the pump motor through the 40A fuse 15.

If you apply power directly to the motor, the pin 1 which is a green/yellow wire is the positive lead, while the brown is the ground lead.

Sal 965

Here is the electrical layout of the relay.

Can i bypass this somehow to get the motor to run without the relay in place to run a simple test. I tried tonight but my High School physics must be rusty - the paper clip i used to bridge the circuits melted the rubber gloves i was wearing



Garrett i obviously didn't understand you. Could you be specific to the electrical layout as this type of work is not my thing. It must be lack of hammer useage

garrett376

Hi Steve.
If you unplug your relay, and look on the Central Electric panel, you will see the terminals I referenced above. Ignore that wiring diagram on the relay itself - it's not too helpful!

Plug 3 into 5 - your motor should run irrespective of the pressure switch.

Sten

Steve,
Did you pop the fuse after your paper clip adventures? Can you hear the pump running? You have a PM!
Barry

tafkai

steve
i have a colour board monitor , and a relay 964 615 135 00 .
waiting here for you
phone me on 07783538889
or if you dont get this message til later , i'll be on my belgium mobile . 0032 478 655125

Indycam

I'd forget the relay jumper , the battery is less than a foot away . Wire up to the battery with test leads.
Don't let it run for long , it can build pressure fast .

2000m2

Very similar situation -- I was cruising along this afternoon when I got warning lights Brake, AWD light and exclamation point at the top. Shortly thereafter my brake pedal was super stiff and braking took a lot longer than normal (YIKES!). Brake fluid level is good/normal in reservoir, fuses 15 & 16 are fine, no brake fluid on the bottom of the frunk or near boost pump. On startup, I usually hear buzzing from the frunk for about 20 - 30 seconds.
My question is how do I know if relay R51 is bad? Looks like they're about $80.

2000m2

Well, as luck would have it, I remembered there were some relays and fuses in the glove box left behind by some old owner(s) and one of them happened to be R51! It looks to me to be the original one as it says made in Germany and has the OEM part number on it. The one in place has no part number, made in Hungary and perhaps dated 2006. I popped the old one back in and everything works as normal. Amazing. I ordered a new one to have on hand just in case.

2000m2

I just received the new Relay from Porsche. Interestingly, it is noticeable taller than the original one, has the part number written on it and made in China. We'll see how this one holds up.