Oil warning light/buzzer problems Subaru Engine

[Azad lost]

I don't know if people will be able to help me with this problem, but it will require many little bits of knowledge, so any information, even its not a solution, will be appreciated.

The vehicle: 87 syncro
The motor: 3.3 Subaru H6 out of an svx

The problem: This is a new problem. Whenever the engine revs above 3800, the buzzer begins sounding and the oil light flashes. This continues until the engine is shut of.

Extra details:

When the key is inserted and turned to the "on" position the oil pressure light flashes only once at the moment the key reaches "on" position. It DOES NOT continue to flash with the key on and engine off as I believe it should in a standard vanagon.

I believe I have located the oil pressure switch on the Subaru motor, behind the alternator. If I unplug the oil pressure switch, the light does not flash or turn on. HOWEVER, if the oil pressure switch is unplugged the buzzer will NOT sound and the light will NOT flash when the engine revs above 3800 rpm

Theres plenty of gaps in my knowledge of the system, so any information helps.

[MarkWard]

The 87 would have had two oil pressure switches. That’s how the system was engineered and wired. So, the Subaru engine would have needed 2 switches as well. If you only have one switch and it was working, the converter likely did something to get it to work and that “trick” has failed.

You should first verify the oil pressure with a mechanical pressure gauge.
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[Azad lost]

Is it possible that the subaru switch was wired to the buzzer in the manner of the high pressure switch instead of the light in manner of the low pressure switch?

[MarkWard]

[wesitarz]

Look up how to disable the hi pressure buzzer on the speedometer.

[MarkWard]

Disabling at the cluster is sort of permanent. I believe since it was working, they'd like to have it working again.

Rather than explaining how the system is supposed to work, here is a recent thread regarding troubleshooting the system. https://www.thesamba.com/vw/forum/viewtopic.php?t=753690

Since it's converted to subaru power plant, without a supplemental wiring diagram, it's going to take some investigating. As I mentioned above, first step is to verify the engine has the correct oil pressure. Your warning could be functioning properly.
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[wesitarz]

[Azad lost]

Oooh, where is this black box? Where can I find information about what’s in it online.

I checked the oil pressure, I can confirm that the oil pressure is fine. Also, while i had a manual gauge hooked up , and the wire to the oil pressure sensor disconnected, the buzzer kept going off regardless.

Now I suppose I can confirm that
1: the buzzer is not connected to true oil pressure
2: no functioning oil pressure warning system of any kind.

I replaced the pressure switch, everything seems to be the same.

[Azad lost]

Also, i’ve been told those colors at the 14 pin connector, but mine dont seem to match up.

Heres a picture of my 14-pin connector.

[hardway]

The Subaru motor did not come with the high pressure switch that is needed for the dynamic oil pressure system to work. Unless it was added it is not there. The stock VW high pressure switch is open below the threshold pressure and closed when above the pressure to provide ground to the control unit in the instrument cluster. If you locate that wire and ground it the buzzer should not sound. It should be a yellow wire in the engine compartment.

[Azad lost]

I understand all that. At this point my interests are more focused around having a functioning oil pressure warning. Helpful info would be:

-Which of the wires on my 14 pin plug goes to the low pressure oil switch originally (it doesnt seem to be yellow)
-which is the high pressure switch wire?
-where could i find the other ends of these wires in the engine bay so i can hook one up to my oil pressure switch.

[wesitarz]

Wire at #12 of the 14 pin connector should be hi pressure (green)-mine is yellow on my 88; wire #13 should be low pressure (blue/ black)
These wires can be found on T7A connector (round 7 pin connector ) in the black box upper drivers side of firewall in the engine bay. The hi press might be the one in the middle according to a schematic that I have.
Try disconnecting the hi press wire. The low press wire should connect to the Subaru oil press sensor

[MarkWard]

I see 3 non factory splices in your harness. Through the years there are a few arrangements of the wires in the connector.

First step would be to meter out which wire is which end to end. If you want to only run the low pressure oil switch, you will need to disable the high pressure switch provision as mentioned above.
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[Azad lost]

Would like to say that everything is fixed now and working great. The low pressure switch works and the high pressure switch is deleted.

The true answer came courtesy of Jeff Robenolt of Autoventures.

It was was the "blue foil" or printed circuit board that was at fault.

When I called Jeff he immediately told me the blue foil was at fault without hesitation, but I resisted because the gauge cluster didn't appear to have any other faults.

Jeff was right.

I replaced the blue foil with a "cluster master" wiring kit from The Bus Depot (CMDT version). And the problem went away. I think the blue foil should be one of the first answers suggested to anyone with an oil buzzer issue.

[MarkWard]

After you verify the engine has oil and pressure.
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[Azad lost]

Haha, Fair enough. And thank you so much for your help. Everything felt better after running a mechanical gauge. I ended up snipping the high pressure sensor wire, and the buzzer kept going off anyway.

[wesitarz]

[quote="Azad lost"
I replaced the blue foil with a "cluster master" wiring kit from The Bus Depot (CMDT version). And the problem went away. I think the blue foil should be one of the first answers suggested to anyone with an oil buzzer issue.[/quote]

The CMDT version deletes the buzzer, which you can do by bending one pin on the printed circuit board behind the speedo.

[rmengr1]

Blue black is low pressure and Yellow is high pressure. Yellow should be grounded. Check to make sure its a strong ground. Blue Black is connected directly to the pressure sensor on the engine. it should be terminal 1 on the round connector in the black box.

Good luck
JB