Frequency Valve Won't Shut Off

At the beginning of July my '87 328 suddenly began running poorly. It sat for a month while we were away - it never sits that long. Last week I traced the problem back to a non-functioning frequency valve. The fused relay was indeed bad as I learned when I attached it to a battery to check it out. The new one plus the other two relays for the O2 sensor arrived today and I installed them. Car started immediately and runs just fine. However, when I shut the motor off and remove ignition key, the frequency valve continues to buzz. The new relay, from Ricambi, has infinite resistance between terminals 15 & 87 when out of the car which I believe to be correct.

I am not worried about running my battery down because I have a big switch on the battery ground so I just disconnect the battery when car is not in use.

Does anyone have any ideas about what might be the problem?

 

With the relay out of the car, measure the resistance from terminal 30 (the +12V power supply) to terminal 87 (the wires going to the FV & inj. ECU) -- this should be infinte ohms. If it is a low value (e.g., a few ohms) the relay is bad (and the switch contacts inside are stuck "closed").

 

The resistance between terminals 30 and 87 is infinite.

 

That's trouble

What are the Bosch part numbers on "the other two relays for the O2 sensor"? -- they should be of the ...101 type (i.e., terminals 30, 85, 86, 87 and 87a).

If those are the correct relays, reinstall the protection relay and please make the following voltage measurements (with the key "off"):

1. terminal 30 to terminal 31 = should be +12V

2. terminal 15 to terminal 31 = should be 0V

3. terminal 87 to terminal 31 = should be 0V

and please report what you find -- hopefully, it will indicate where to go next.

 

The number on each of them is 0332204101.

 

That's good -- just wanted to make sure that you received the correct ones (since that was something else that had been "changed" before your odd behavior). Although if the old ones were OK, wouldn't hurt to put them back in just to make sure the new ones aren't part of the problem.

Please advise the voltage measurements -- for example, if terminal 15 is at +12V with the key "off", it wouldn't be "right" (and would be the next area of investigation), but it would exonerate the new protection relay as the protection relay should close (and run the FV) when terminal 15 is at +12V.

 

I put old relays in and the thing still buzzed. I have noticed that there is no voltage to terminal 15 when I check it to ground. But I have noticed something very weird. As I pressed the fused relay into its holder with the battery hooked up, the FV buzzed. If I quit pushing on the fuse, it quit buzzing, so on and so forth. If I hold the relay by the aluminum exterior and press on the fuse, the FV goes on and off as I press and release. The contacts for the fuse go all the way to the circuit board area of the relay...I have my old one apart.

 

If terminal 15 is not at +12V, but the FV starts buzzing, it does sound like something (the PCB?) is flexing inside and (wrongly) connecting terminal 87 to +12V. Since you say "if I quit pushing on the fuse, it quit buzzing" is it now working OKish (since, when normally installed/used, no one would be pushing on it)?

 

One last observation. With the relay not fully inserted so there was no buzzing, so I started the engine and it ran poorly. While running, I shoved the relay in the rest of the way and engine ran normally. I removed relay and inserted a spade into terminal 15 in block. It had no voltage. This was just a double check to make sure I checked 15 correctly. Terminal 30 has 12+ volts all the time.

So I may have misled you on my previous post.

 

I think what I need to do is to make up 4 spaded wires with alligator clips on the other end and attach to relay and terminal block. That way relay will be attached yet I can easily measure voltages to see what is linked to what. As it now stands, if I do not push relay fully into block, it is not making contact on all terminals.

 

Here are voltages with key off:

30-31 11.94v
15-31 0V
87-31 11.94v

One has bad reading. FV was buzzing the whole time.

 

I have to say that the greatest likelihood is a bad (new) protection relay, but there is one other test to definitely confirm/deny. Remove (only) the 3 PN (beige/black) wires from terminal 87 (while leaving all of the other wires still connected):

If the voltage between terminal 31 and the now bare terminal 87 is still +12V (while the 15-31 voltage is still 0V), then you can be absolutely sure that the (new) protection relay is bad.

If the voltage between terminal 31 and the now bare terminal 87 is 0V (while the 15-31 voltage is still 0V), then you have a really strange problem elsewhere that I hope we don't have to find

 

Pardon the silly question but what does PN mean?

 

PN = the symbol used on the schematic to describe the color of the wire insulation for identification = beige/black

 

I did the test. Relay terminals 15 - 31 is 0 V. From 31 - 87, I measure 12+V. This measurement was taken from relay posts. If I go 31 to disconnected lead 87, I get 0 V.

With 87 removed, FV is silent.

 

OK, I think that means, unfortunately, that you need another new protection relay, but just to clarify:

"From 31 - 87, I measure 12+V" -- this means that you still measured +12V from terminal 31 (with the black wire connected) to the bare male 87 terminal on the protection relay (no wires connected),

and

"If I go 31 to disconnected lead 87, I get 0 V" -- this means that measuring from terminal 31 (with the black wire connected) to the unplugged female terminal with the 3 PN (beige/black) wires in the wiring harness you got 0V.

If so = you need another new protection relay

 

It sounds like we are on the same page. Here is another attempt by me to remove all doubt about what I measured.

I unbolted the block from the lid so I can hold block and relay in my hand. I took a small screwdriver and removed the brown/black lead from relay block which plugs into 87. There is a little tab that releases the wires from the relay block. At this point I have relay plugged in but female brown/black wire is free. Terminals 15, 30, 31 are connected to relay.

When I measure, I put the probes in the back of the relay block. 15 - 31 gives a 0 V reading. When I put the probes in the back of the block and measure voltage between 31 (connected) and 87 which is bare (because I removed the wires), I get 12 V. If I measure from 31 by again sticking the probe in the back of the terminal block while the other probe is on the free wire that was disconnected from 87, the voltage is 0.

So it looks like a yes, yes. Darn, this is an electrical part.

 

Unfortunately, yes...

 

Would you know if the protection portion of the relay still working? I always shut the main battery ground switch off when I leave the car.

 

Not possible to make a conclusion about this from the limited information available (and are you really going to disconnect the battery everytime you go to the store, get gas, etc.? -- doesn't seem practical to me). Even though the electrical parts are not returnable, perhaps the supplier will give you some price consideration on a replacement. Alternatively, the RA price isn't too bad IMO ($110).

 

Thank you for all the help in this matter.

 

^ I'm sending a replacement today at no charge. Who knows if it was DOA at my place, or FedEx smashed it. No worries... you'll have a replacement tomorrow.

 

And thank you Jack Russel Racing..

 

The replacement frequency valve/protection relay arrived this morning. I plugged it in and car runs fine. The replacement also shuts off the frequency valve when I shut down the engine. All is fine now.

Ricambi exhibited excellent customer service. They have gained a new customer.