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  View original topic: Oil Pressure light buzzer wiring
mattbobsquarebus Sat Sep 12, 2009 6:35 pm

I've put about 1000 miles on my 87 Vanagon now, and still have not solved the intermitant oil light/buzzer. This engine came from another van, which I only drove about 200 miles before pulling the motor but the light never came on. Ever since the swap, the light comes on at least once every time I drive. First I changed to Castrol 20W50 and a OEM filter. Then flushed and replaced the coolant. Most recently, I replaced both pressure switches. I also confirmed pressure with a mechanical gage and the readings are good.

Recently this is even worse. The light comes on as soon as the engine RPM goes over 2100K or so, and stays on until I stut the engine off. I pulled the wire from the sensor yesterday and it acts exactly the same, which I guess indicates a wiring issue.

So finally a question; Are there any common areas of failure to check with the wiring? I've only checked the wire on the block from the 2 pole connector to the sensor by the waterpump.

Thanks,

larrytrk Sat Sep 12, 2009 6:39 pm

I had to run a new wire from the connection in the back to the front into the connector for the foil to solve a similar problem..Now all is fine.

jdrudge Sun Sep 13, 2009 4:01 pm

I would check with a mechanical gauge- install where your low pressure sending unit is on the side of the block. Compare with the spec in the Bentley manual at around 176 degrees (at you oil filter)- I believe @ 2000 RPMs.

Did you get a VW sending unit or one from your local auto parts store?

Josh Drudge
1990 Vanagon
1974 Thing

?Waldo? Sun Sep 13, 2009 4:23 pm

There are two pressure senders, one for low pressure which is normally closed and opens when oil pressure gets above a few psi. The high pressure switch is NORMALLY OPEN and closes when pressure gets above 20 psi or so. The high pressure switch is looked at by the system when the rpms go above 2,000 or so. To test the circuitry, you should have GROUNDED the high pressure switch wire in order to simulate oil pressure above 20 psi at 2,000 rpms.

Andrew

mattbobsquarebus Mon Sep 14, 2009 8:21 pm

Andrew A. Libby wrote: There are two pressure senders, one for low pressure which is normally closed and opens when oil pressure gets above a few psi. The high pressure switch is NORMALLY OPEN and closes when pressure gets above 20 psi or so. The high pressure switch is looked at by the system when the rpms go above 2,000 or so. To test the circuitry, you should have GROUNDED the high pressure switch wire in order to simulate oil pressure above 20 psi at 2,000 rpms.

Andrew

That makes sense. I'll ground the lead for the high pressure switch and go for a ride...

The new switches are from Van Cafe, they are German made but I don't know anything else about them.

Thanks,
Matt

stevey88 Mon Sep 14, 2009 9:40 pm

Check the plug and socket inside the black box mounted on the fire wall. All the wiring from the engine compartment is plugged into the wiring loom that run from the back to the front inside this box. You have to trace the two brown wires from the two oil pressure switches to the two pin connector that is dangling near the thermostat housing and then to the connector inside the black box. The wires that run to the instrument panel from the connector are yellow and blue/black. Unplug the connector to see if the pins are corroded. Use a meter to see if you have continuity from the two brown wire to the instrument plug ( pin 12 and 13 ). In the case of the oil pressure switches, it goes like this - switch to connector T2 to connector T7 to fuse box and then from fuse box to the plug of the inst panel. Hope this helps.

mattbobsquarebus Fri Sep 18, 2009 7:21 pm

Thanks Guys!

I jumped the wire out as Andrew described and I still had the light. Then I traced the wires into the box on firewall and re-seated these connectors and it seems to have solved the problem.

I plan to grease the connectors to prevent any corrosion and off I go...



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