911SC Frequency Valve problem

[SCadaddle]

Gents:

Apparently my Frequency Valve or FV as it is known around here is not operating. I've searched and searched, found a few things to diagnose but still no cigar.

Known:

1) Interior dome lights and glove box light are working
2) Have power all the time at female terminal 30 of the O2 sensor relay under the passenger seat all the time
3) Have no power at 86 with key on (should I?)
4) Lifting the throttle plate in the air box does not turn on the FV
5) Have tried 2 other relays to no avail
6) Connector at FV appears fine

Can anyone offer something else to check? Is there a diagnostic to actually bench test the relay? Thanks!

[john walker's workshop]

you need power out of the relay at both 87 terminals. one to the computer, one to the fV. the plug on the rear shock crossmember can be corroded or have a broken wire. same with the relay plug. usually it's something other than the FV.

[Peter Zimmermann]

John beat me to this post! I was going to say, have you checked the harness quick disconnect that's just inboard of the LR upper shock tower?

[Scott R]

I may be way of track here, but I once worked on an SC that had the CSV plugged into the FQ valve, but it didn't last long and melted the FQ valve in the end. Hard starting, and poor running, go figure?

[SCadaddle]

Well, I've since managed to find a document to bench test the relays here:

Relays

and with the assistance of an Electrical Professional Engineer aka "my neighbor" we sorted out that both the Bosch relay which was less than a couple months old that was in the car, along with a new Bosch relay from the local NAPA store both exhibited no continuity between 30 and 87A yet had continuity between 87 and 87A (the switch), yet the third relay also from NAPA, made in China, did exhibit the correct functions: continuity between 30 and 87A and no continuity between 87 and 87A....the difference being both the Bosch units were tried in the car and the made in China one not.
So I tried the Chinese relay and still no go. Bench tested it afterwards to see if something in the car is burning them out and it is OK.

I've checked the plug at the shock tower and it is secure. John Walker states I should have power out at both 87 and 87A....can I detect that by simply probing the relay plug with a test light and does it matter ignition on or off?

[schumicat]

I think you're reading the relay wrong. 85 is ground, 30 is +12 volts from the fuse, only when 86 has +12 v also does it lets the power flow to 87 and 87a.

[boyt911sc]

Originally Posted by SCadaddle

Well, I've since managed to find a document to bench test the relays here:

Relays

and with the assistance of an Electrical Professional Engineer aka "my neighbor" we sorted out that both the Bosch relay which was less than a couple months old that was in the car, along with a new Bosch relay from the local NAPA store both exhibited no continuity between 30 and 87A yet had continuity between 87 and 87A (the switch), yet the third relay also from NAPA, made in China, did exhibit the correct functions: continuity between 30 and 87A and no continuity between 87 and 87A....the difference being both the Bosch units were tried in the car and the made in China one not.
So I tried the Chinese relay and still no go. Bench tested it afterwards to see if something in the car is burning them out and it is OK.

I've checked the plug at the shock tower and it is secure. John Walker states I should have power out at both 87 and 87A....can I detect that by simply probing the relay plug with a test light and does it matter ignition on or off?

SCadaddle,

There should be no continuity between terminals 87a and 87 at anytime!!!!! These are two (2) separate terminals. When the FP is activated the OXS (FV) relay is energized @ terminals #86/#87a, making the normaly closed #30-87a to open and becomes #30-87 configuration (normally open) and power from fuse #18 supplies power to terminal #30 (hot all the time).

In summary, the FV relay terminal #87a gets power directly from the FP relay @ #30 and #87 (FV relay) from fuse #18. There is no continuity between terminals #87a & 87.

Tony

[schumicat]

Re the bench test, connect 85 to ground, 30 and 86 to +12 v. connect test light clip to ground. when test light probe touched to either 87 and 87a it should light up. if you then disconnect either 30 or 86 from +12 volts the test light should not light when touching either 87 and 87a.

[boyt911sc]

Originally Posted by schumicat

Re the bench test, connect 85 to ground, 30 and 86 to +12 v. connect test light clip to ground. when test light probe touched to either 87 and 87a it should light up. if you then disconnect either 30 or 86 from +12 volts the test light should not light when touching either 87 and 87a.

Andy,

You have explained the detail as clear as sunlight!!!!! We both are in the same page about this thing including the test. And I'll give you a ten (10) for the detailed info.

Tony

[SCadaddle]

Originally Posted by boyt911sc

Andy,

You have explained the detail as clear as sunlight!!!!! We both are in the same page about this thing including the test. And I'll give you a ten (10) for the detailed info.

Tony

As outlined, here are the results:

2 month old Bosch relay that was in the car:

Ground to 85
+12V to 30
Touch +12V to 86 and direct short complete with sparks

NAPA Bosch relay (new today)

Ground to 85
+12V to 30
+12V to 86 and hear a click as it is connected
Test light to clipped to ground
Light at both 87 or 87A
Remove +12V at 86 no light at either 87 or 87A

NAPA Chinese relay (new today)

Ground to 85
+12V to 30
+12V to 86 and hear a click as it is connected
Test light clipped to ground
Light at 87 only
disconnect +12V at 86
Light at 87A only


Go figure!

[boyt911sc]

Originally Posted by SCadaddle

As outlined, here are the results:

2 month old Bosch relay that was in the car:

Ground to 85
+12V to 30
Touch +12V to 86 and direct short complete with sparks

Go figure!

Are you testing the relay out or plugged to a relay socket? Or directly to the relay?

Originally Posted by SCadaddle

As outlined, here are the results:

NAPA Bosch relay (new today)

Ground to 85
+12V to 30
+12V to 86 and hear a click as it is connected
Test light to clipped to ground
Light at both 87 or 87A.........................................87 (yes), 87A (no).
Remove +12V at 86 no light at either 87 or 87A.....................correct!!

Go figure!

The above test results are correct!!!! if you are using a relay socket?

Originally Posted by SCadaddle

As outlined, here are the results:

NAPA Chinese relay (new today)

Ground to 85
+12V to 30
+12V to 86 and hear a click as it is connected
Test light clipped to ground
Light at 87 only.............................................. ......correct.
disconnect +12V at 86
Light at 87A only.............................................. ....correct.

Go figure!

The above test results are correct if you are not using a relay socket!!!!!

There are some discrepancies in the test results but we don't know exactly how you tested the relay. Did you use a relay socket or simply tested the relay directly. Double check if you have misread the pin ID.

Test your relays for continuity between pins #86 and #87A........there should be NONE unless you are using a relay socket that is bridged. Keep us posted.

Tony

[SCadaddle]

Tony,

The method to (bench) test the relays were having just the relay sitting on my table and making connections with alligator clip jumper leads to a 12V battery and circuit tester light (static timing light from my VW days).

[boyt911sc]

Originally Posted by SCadaddle

Tony,

The method to (bench) test the relays were having just the relay sitting on my table and making connections with alligator clip jumper leads to a 12V battery and circuit tester light (static timing light from my VW days).

Test the continuity between each pin:

#86 - #85............yes
#86 - #87a..........none
#87a - #87..........none
#87a - #30..........yes (NC)
#87 - #30............none (NO)

A good working relay should have these conditions. The last test you did was OK. Keep us posted.

Tony

[SCadaddle]

Originally Posted by boyt911sc

Test the continuity between each pin:

#86 - #85............yes
#86 - #87a..........none
#87a - #87..........none
#87a - #30..........yes (NC)
#87 - #30............none (NO)

A good working relay should have these conditions. The last test you did was OK. Keep us posted.

Tony

2 month old Bosch relay:

#86 - #85............yes YES
#86 - #87a..........none NONE
#87a - #87..........none YES
#87a - #30..........yes (NC) NO
#87 - #30............none (NO) NO


New NAPA Bosch relay

#86 - #85............yes NO (shows about 84 ohms)
#86 - #87a..........none NONE
#87a - #87..........none YES
#87a - #30..........yes (NC) NO
#87 - #30............none (NO) NO



New NAPA chinese relay

#86 - #85............yes NO (shows about 84 ohms)
#86 - #87a..........none NONE
#87a - #87..........none NONE
#87a - #30..........yes (NC) YES
#87 - #30............none (NO) NO

[boyt911sc]

Originally Posted by SCadaddle

2 month old Bosch relay:

#86 - #85............yes YES
#86 - #87a..........none NONE
#87a - #87..........none YES
#87a - #30..........yes (NC) NO
#87 - #30............none (NO) NO


New NAPA Bosch relay

#86 - #85............yes NO (shows about 84 ohms)
#86 - #87a..........none NONE
#87a - #87..........none YES
#87a - #30..........yes (NC) NO
#87 - #30............none (NO) NO



New NAPA chinese relay

#86 - #85............yes NO (shows about 84 ohms)
#86 - #87a..........none NONE
#87a - #87..........none NONE
#87a - #30..........yes (NC) YES
#87 - #30............none (NO) NO

SC,

How is your VOM set to test the continuity? If you could get 84 Ohms reading across the pins then it is not OPEN???? The reason why you are getting a reading across the pins (#85-#86) is because of the coil for the switch between these pins. I'll try to explain why for each set of pins:

#86 - #85............there is a coil between these pins, so there is continuity.
#86 - #87a..........none, because they are 2 separate and insolated pins.
#87a - #87..........(same as above)
#87a - #30..........Yes, because these are NC (normally closed) pins.
#87 - #30............none, because these are NO (normally open) pins.

The switching arm is pivoting @#30:
#30-#87a.......these are NC when the coil between #86-#85 is not energized.

When you energized (#86-#85), the NC condition (#87a-#30) goes to goes to #87-#30. Do you still follow the logic? The best way to understand the sequence of the relay is to draw and visualize the switch from #87a-#30 to #87-#30.

Tony

[SCadaddle]

Tony,

I'm using a small pocket sized Radio Shack Auto Range Digital Multimeter. Under one switch position I can press a button to change from -I>+, audible tone with display of either OPEN or SHORT, and lastly Ohms. I've got it set for the audible tone and display of either OPEN or SHORT for all the tests, and on 2 of the relays: the new Bosch one and the Chinese version testing 85 to 86 displays OPEN while the 2 month old Bosch relay displays SHORT with the tone. When I switch to Ohms the new Bosch and the Chinese relay indicate about 84 OHms across 85-86.

What are the chances of having 3 relays that don't work correctly? I understand the concept of the "switch" at 87 and 87A yet both of the Bosch relays show continuity between 87 and 87A. "Energizing the coil" is the concept perhaps I'm not grasping, I'm thinking if I pass 12 volts through the coil via 85 and 86 I'm going to cause a short and fry it?

I'm getting tempted to take an Xacto saw and open these guys up if nothing else to see what is going on between 87 and 87A!

[boyt911sc]

Originally Posted by SCadaddle

Tony,

I'm using a small pocket sized Radio Shack Auto Range Digital Multimeter. Under one switch position I can press a button to change from -I>+, audible tone with display of either OPEN or SHORT, and lastly Ohms. I've got it set for the audible tone and display of either OPEN or SHORT for all the tests, and on 2 of the relays: the new Bosch one and the Chinese version testing 85 to 86 displays OPEN while the 2 month old Bosch relay displays SHORT with the tone. When I switch to Ohms the new Bosch and the Chinese relay indicate about 84 OHms across 85-86.

What are the chances of having 3 relays that don't work correctly? I understand the concept of the "switch" at 87 and 87A yet both of the Bosch relays show continuity between 87 and 87A. "Energizing the coil" is the concept perhaps I'm not grasping, I'm thinking if I pass 12 volts through the coil via 85 and 86 I'm going to cause a short and fry it?

I'm getting tempted to take an Xacto saw and open these guys up if nothing else to see what is going on between 87 and 87A!

SC,

The term 'energize' is just a terminology that refers to a load (resistance) being supplied with power (voltage) to complete the circuit. For example let us use a device like a light bulb. The light bulb has a positive (+) and a negative (-) contacts. Applying voltage to the (+) will not lit the light bulb unless the (-) is connected to the ground to complete the circuit. When I turned the light ON, the bulb has been energized.

Now let's go back to the relay, assume this time instead of a light bulb we have device (load) like the thing inside the relay between #86 & #85. Let's just call it 'coil' or whatever. Applying 12 volts to #86 does nothing to the device unless the circuit is complete. Meaning #85 has to be grounded to complete the circuit.

So when you energize the 'coil' (switching arm) it goes from #30-#87a NC (normally closed) configuration to #30- #87 NO (normally open) configuration.

Still follow the logic?

Now to answer your question, if you apply 12-volts to #86 and #85 is grounded you have activated the switch (coil) or energized the switch (coil) or whatever name you want to refer to it. As long as you supply the correct amount of voltage and there is no short in the circuit, you won't fry or burn the system.

BTW, the new Napa (Chinese) relay test results indicate it is GOOD. There is continuity between #85 & #86 based from your test (84 Ohms).

Tony

[SCadaddle]

Ok, here are the relays involved.

From left to right: 2 month old Bosch that was in the car, NAPA Bosch, NAPA Chinese version. Last night I opened up the original 2 month old Bosch. Terminals 87 and 87A are certainly linked together on the same circuit. Closer inspection of the diagram on the relays indicates this.




Tony tells me the "Chinese relay" should be good to go. Let's move on the receptacle in the car (82SC USA) under the passengers seat.

1) I've got continuous power to socket 30
2) I've got a good ground at socket 85
3) I've got no power at socket 86 with the key on
4) 87 and 87A should be the computer and the FV--how to test?

EDIT: Battery disconnected, key off, I ran a long wire from socket 86 through my VOM to the fuse block in the front trunk and fuse #20 (air conditioning) and I do have continuity through that circuit.

Known history of the car: When I bought it last June the fuel pump relay was non-existant and had a jumper wire, the O2 sensor was not connected and the CIS must have been tuned to run with that condition. Recently built engine including inspecting/replacing CIS components. Found wiring to the O2 relay under the passengers seat melted. Sorted that out with new wire and found the wire in the front trunk disconnected. It got connected to fuse #20. Of course there is a non-functioning Clifford Alarm system in the car. All systems "go" the CIS was tuned. Car ran like a bat out of hell then one day started running really bad. My all time favorite 911 Guru and Master of all things Porsche, BMW and Mercedes (and the occasional Lexus since it is "family"!) is awaiting delivery of the car via truck and trailer scheduled in the next 24 hours. I'm just trying to trouble shoot what I can....

[theiceman]

as you probably know the 2 relays on the left are different from the one on the right
The two on the left have two normally open connections ( NO ) 87 and no Normally closed Connection (NC)

The one on the far right has one NO connection 87 and one NC 87A

that is why they are not lableled "87A" in the first two relays , they are both correctly labelled 87

[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