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Date:         Fri, 3 Dec 2010 09:41:43 -0500
Reply-To:     Dennis Haynes <d23haynes57@HOTMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <d23haynes57@HOTMAIL.COM>
Subject:      Re: oil pressure warning system anomaly?
Comments: To: mark drillock <mdrillock@COX.NET>
In-Reply-To:  <4CF8981A.9040803@cox.net>
Content-Type: text/plain; charset="us-ascii"

If key on engine off has the light off, and then starting the engine turns the light on then the sensors or the wires are reversed. The low oil pressure/blink the light sensor should be located at the port between the push rods. This sensor is normally closed (on) and opens when sufficient pressure is there. The higher pressure sensor (2000 rpm buzzer) is at the rear of the engine. It s normally open (off) and closes with sufficient pressure. This if the wires to the two sensors are reversed the light operation will be backwards and you will get the warning buzzer to sound when the engine rpm goes above 2000 rpm.

Dennis

-----Original Message----- From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of mark drillock Sent: Friday, December 03, 2010 2:11 AM To: vanagon@GERRY.VANAGON.COM Subject: oil pressure warning system anomaly?

Today I was working on a very recent addition to the family van fleet, a 90 pass van, 2.1 auto towed home yesterday. It was knowingly bought with a massive oil leak as soon as the engine was started and was presumed to need a new engine based on assertions by the seller. Changing the oil cooler o-ring fixed the leak. However, the oil pressure light would not stop blinking, even if the rpm was raised.

After unplugging the 2 pin connector to the oil switches, I used an ohm meter to determine that the low rpm switch was grounded when engine was stopped and went to open circuit immediately when engine was started or even cranked briefly. I verified that the oil light worked by grounding the wire to it from the low switch with the key turned on. The light would blink when grounded and stop blinking when the wire was unplugged.

In spite of the above all normal test results, when the 2 pin connectors were joined, the oil light blinked constantly while the engine was running. The blinking stopped as soon as it was unplugged again. Again the switch itself showed open circuit while the engine was running. What the heck?

Curious as to what was going on I unplugged the 2 pin again and bridged the in and out ends of the low switch wire with a test jumper so I could measure the voltage on the wire with the meter. NOW the light stops blinking when the engine starts and resumes blinking if I stop the engine by pulling the coil wire! WORKS normally.

In frustration I removed the jumper and plugged the 2 pin back together. Again the light stays blinking after the engine starts! My nephew then points out that the only difference is that it worked fine when only the one switch was wired up by the jumper but doesn't work when both switches are wired up as they are supposed to be. I grabbed some cutters and clipped the wire coming from the high pressure switch. Now the oil light works! Blinks with just key on, goes out when engine starts, comes back on if engine is manually stalled.

Of course the dynamic oil pressure warning circuit board is supposed the ignore the high pressure switch until the rpms reach 2000 or above so the wire I cut should not make any difference below that. I was out of time for the day and did not pursue things any further yet. I don't know what to think at this point. I may call the seller to ask if they had been driving around with the oil light blinking for some time. If so, the leak from the cracked oil cooler o-ring may have been undetected before damage was done to the engine.

Mark


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