911SC Frequency Valve problem

[john walker's workshop]

a couple of jumper clips between 30 and both 87s and it should run w/FV function if the rest of the system is OK.

[Peter Zimmermann]

[SCadaddle]

Peter,

The "2 month old Bosch relay" was sourced from our host on 10/11/12 as invoiced part number PCG-951-253-00. It was the one that was in the car and also the one I cut open. It is on the far left. The others from NAPA supposedly the correct part.





John,

That's an idea. An "under the seat toggle switch that works better than any Clifford alarm as the car aint worth stealing if you don't know about it!"

[john walker's workshop]

for test purposes of course.

[Peter Zimmermann]

Does this help?

[SCadaddle]

Originally Posted by Peter Zimmermann

I've been wanting to ask...are we using relay P-car part # 821 951 253?

It should have:
1x 30
1x 85
1x 86
1x 87
1x 87b

Peter,

I just called my local Porsche dealer, supposedly that part number has been superceded to PCG 951 253 00 which is what our host sent me?

[SCadaddle]

Originally Posted by Peter Zimmermann

Does this help?

Ahhh, that is money! Continuous power to 30, "energize the coil" between 85 (the ground) and 86 (+12V) clicks the arm to complete the circuit to 87 and 87A (or 87B). Got it.

So at the connector in the car, I've got continuous power at 30, a good ground at 85, continuity between 86 and the fuse block in the front of the car. For the life of me, IF the circuit between the fuse block and 86 is "switched" via the ignition key, how could I have continuity with the battery disconnected and the keys in my pocket?!

EDIT: Ah, ok sports fans. Battery connected, key in ignition. Hook test light between 85 and 86. Turn key to run position....nothing. Nothing that is until I lift the air sensor in the air box for just a second that turns on the fuel pump. Test light turns on. This pup should run with the correct relay....

[boyt911sc]

SC,

You are just a step behind (slow) and you'll catch up. Your test light should be hooked to #86 (OXS / FV relay). As you have found, terminal #30 is hot at all time (from fuse #18). Terminal #86 (power to coil) gets power from the FP relay @ 30.

The FP must be energized @ #30 (FP relay not FV relay) for the FV to operate. Lifting the AFS (air flow sensor plate) with the ignition @ ON/RUN makes the FP to run thus supplying power to #86 (FV relay). Follow the logic?

Review the FP relay and you'll find that it supplies power to the OXS/FV relay's #86 terminal. BTW, we wasted so much time because you were using the wrong type of relays in our discussion. It was obvious in the diagram on the face of the relays that they were different from each others.

Tony

[SCadaddle]

Tony,

Humbly agree. Should have posted a picture of the players right off the bat. The pair of Bosch relays are nearly identical, one apparently having a diode at 85-86. The Chinese relay just flat out wrong part. Chock it up to "NAPA know how" I guess. Good thing I bought one of each they claimed was the "correct" part....

Updated status is the system at the relay anyways appears to function. As I outlined this afternoon, I swapped in the relay for the test light, ignition on raised air sensor plate and the fuel pump started which made the relay "click". Still no FV best I can tell.

I'd like to sincerely Thank all those that chimed in and helped me with this. Learned some things and made progress. Hopefully one day I can return the favor and perhaps someone in the future that finds this in a search will benefit from it.

As for me, I am counting the hours before I have to go before the Guru of all things Porsche, BMW and Mercedes and put back in my place.

(where's my ear plugs?)

[Peter Zimmermann]

SC; if you're at the engine compartment you'll be able to easily hear the FV when it starts running. It makes a distinct buzz...