A common problem with 86-91 2.1l Vanagons is the flashing oil light with buzzer sounding. This article only effects 86-91 2.1l waterboxer Vanagons. If you have an earlier Vanagon (80-85) please refer to my previous article about the oil light coming on:
I want to stress that if your oil pressure light comes on, please pull over immediately and shut the engine off. Don’t let the fact that you read this article and you think that you know why this is happening and it is just a normal thing for Vanagons stop you from doing what common sense dictates. You never know if what you are experiencing is a real oil pressure problem or a false alarm. It is not worth taking the chance, pull over, and check things out!
Usually folks experience the oil light flashing/buzzer syndrome after extended driving. You go to get off at an exit ramp and then the oil light comes on flashing and the buzzer sounds. What is going on?
1. Understanding how the system works
First of all let us understand how this system works. You have two oil pressure senders which are monitored by a control board located behind your speedometer. One sensor is located in the base of the engine between the push rod tubes. This is called the .3 bar sensor and the plastic part of it should be brown in color. This sensor is for the oil light only (no flashing or buzzer). This is the same sensor that has been used on VWs for the past 30 years. It senses when the oil pressure falls below .3 bar (around 5 psi). At this point the sensor grounds itself and the light comes on. The control board only looks at the input from this sensor when the rpms of the engine are below 2000.
The other sensor is located near the water pump. This is the sensor that causes the oil light to flash and the buzzer to sound. You should see a brown wire going down near your ignition distributor to this sensor. This is called the .9 bar sensor. The control board that monitors the two sensors only looks at this one when the rpms go above 2000. How is works is when oil pressure is above .9 bar (aprox 13.23 psi) the switch inside the sensor is closed. This grounds the sensor and this keeps the light off. It works the opposite of the .3 bar switch which comes on when it is grounded. As you rev the engine above 2000 rpm the control board looks at this switch to see if it is still grounded. If it is the oil light and buzzer stay off. If the pressure goes below .9 bar while the engine is above 2000 rpms then the switch inside the sensor opens (pressure holds it shut) and the buzzer and flashing light start.
2. Troubleshooting the problem
Now that we know how these sensors work we can start to troubleshoot them. First of all the .3 bar sensor and it’s problems and methods of troubleshooting have already been addressed in an earlier article https://www.vanagain.com/flicker1.htm. If you are having the oil light flickering or flashing on and off at idle then please read this article. However if you are having the oil light come on flashing with the buzzer then continue.
The very first thing to check if you are having this problem is the oil level. If you are low on oil your oil pressure can get low. This is why this warning system is there to prevent us from having problems due to an oil leak or our own negligence.
Next you want to be sure that your oil is clean and not diluted with gas. Smell the oil. Does it smell like gas? You may have a leaky injector that is diluting your oil. This will thin it and reduce your pressure.
What weight oil are you using? I would recommend 20w-50 oil for all waterboxer engines that have over 100k miles on them. If you are using a lighter weight oil try changing the oil and see if this helps.
What oil filter are you using? You want to see a black oil filter on the engine. Mann or Mahle or VW filters ONLY! Fram, Bosch, and any other color of the rainbow (blue, red, yellow, grey, etc.) can cause a low oil pressure condition so don’t use them.
Now that we have covered the basics you want to check the wiring to the .9 bar sensor. As we have said the sensor tells the buzzer and light to come on when the control board sees an open in the circuit. This could be caused by the sensor or it could also be caused by the wiring going to the sensor if it becomes broken somewhere along the run. You can easily test this by unplugging the wire from the sensor and grounding it to the engine of the van (usually there is a male spade connector on the side of the ignition distributor where you can plug this wire into). If the wiring is good then your oil light and buzzer will stay off at all times. If there is a break in the wiring usually the buzzer and light will come on immediately upon revving the van above 2000 rpms. At this point you are going to need to examine the wiring, try to find the break and repair it.
If you have grounded the sensor wire and it has made the buzzer and flasher stop the next step is to replace the sensor. You could check the sensor with an oil pressure gauge and wiring up a light to show you when the sensor is grounding or not but most folks don’t have the skill or equipment for this. If you do this is outlined in the Vanagon Bentley Manual. If you don’t then I would suggest just buying a new .9 bar oil sensor as they are only $6 and they are a wear item that should be replaced every 100k miles or so. Be sure that when you get the new switch the plastic part of the body is gray in color and the part number is 068919081A. This is the correct part number for this part. There is much confusion going on about this part and what the proper part number is so be sure to have the part number with you when you go to order this part to avoid getting the wrong sensor.
If you replace the sensor, plug the wire back onto it and you are still getting the oil light flashing with the buzzer then you need to have the oil pressure tested. You can do this yourself by purchasing an oil pressure test kit, or take it to a local shop and have it tested. You want to do the test with the engine warmed up (radiator fan having cycled on and off once). At 2000 rpm the oil pressure should be 19 psi or higher (19 psi is the minimum at 2000 rpm). If your oil pressure is below this then you probably have some worn engine parts like rod or main bearings and you should start saving money for an engine rebuild. Some folks install a higher volume oil pump to increase oil pressure. We sell this heavy-duty oil pump and it may work for a while (another year or so) but it is only a temporary fix for a tired engine.
If you have your oil pressure tested and it is above the minimum then you probably have a problem with the control board that controls the buzzer and flashing light. This is an “L” shaped board that lives behind the speedometer. Simply remove your speedometer and you will see it. We have these for sale as well if you find you need one. If you replace this board and you are still having problems (it happens) then you may have a problem with the printed circuit foil on the rear of the instrument cluster or the tachometer. The control board is getting a signal from the tachometer and if something is not right at the tach or with the foil circuitry in between then this could cause a false alarm.
At this point you have three options. You can continue to have the oil light flash and the buzzer come on at random intervals (very disturbing to say the least) and just ignore it (not a good idea but many people do). Second choice would be to continue to try to track down the problem by replacing the instrument cluster, etc. This can get expensive. Or you could go with the third option which would be to install an oil pressure gauge and just ground the sensor wire to the engine. This way you can monitor your oil pressure yourself with the gauge and the buzzer and light will never come on again. The flickering oil light will still work below 2000 rpm so you will still have the idiot light at idle. Many people do this and it is a good idea to install an oil pressure gauge so that you can know what is going on with your motor. You could mark the danger zones on the gauge with red tape just incase someone besides yourself is driving the van.
Now you know all that I know about the oil light flashing and buzzing problem. I hope this helps answer your questions. If you need any parts please feel free to give us a call or email or order on-line through our web store.