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Sun Mar 21, 2010 8:17 pm

The oil pressure light comes on randomly when i drive, even though I just put in new oil and I do not think there is anything wrong with the oil pressure. It turns on and off while driving, and you can stop the buzzer/light by shutting off the engine and restarting. There must be something wrong with the reader

There are three different switches at Autozone. They seem to have different BAR ratings.

0.3 BAR Brown

1.4 BAR. Black

0.9 BAR/ Gray

I have not idea what those ratings mean either the BARs or the color.

Sun Mar 21, 2010 8:35 pm

As it so happens, I've been having a similar issue. There is a risk in operating the engine, tho it may NOT the low oil pressure. What year is your Vanagon?

Summary of Threads I put together for a 1986:

--------------------
the 2.1 hi-Oil Pressure switch has a 0.9 bar pressure setting. Some
may have a 1.8 bar switch -- way too high. The Bently '88-89 wiring
diagrams shows 1.8 bar but it may a be a printing mistake. If it were
a 1.8bar switch you would get tons of nuisance warnings.
On 1986-on Vanagons, there are 2 oil pressure sensors (switches). The
switches work in opposite modes. The low-OP switch, to which the
blue/black wire should connect, is a normally closed (NC) switch. It
connects the wire to ground until pressure rises to about 3-4 psi,
when it opens. Grounding the wire completes the circuit for the the
idiot light, so when the OP rises to 4psi te circuit is opened and the
idiot light goes out. This is how just about every car in existence
works as far as the oil idiot light works. So far so good.

The second, hi-OP switch, works in the opposite mode; it is a
normally-open (NO) switch. The yellow wire goes to it. It leaves the
yellow wire ungrounded until OP rises to about 11-12psi. When pressure
is above that level it opens, ungrounding that circuit that the OP
warning system looks at. If the revs are above 2000 and the hi-OP
switch is ungrounded, the buzzer goes off and the light blinks.
- 10cent life

The buzzer will also not operate unless the vehicle is driven (i.e no
buzzer if low OP in neutral?)???

The right (high) switch is P/N 068 919 081A.

http://www.van-cafe.com/home/van/page_357_689/oil_pressure_switch___gr
ey_.75___1.05_bar._mounts.html

Renew both OP switches every so often; they do get sticky, but worse
is they can begin to seep oil, then suddenly turn into a big leak.
Located below and to the right of the water pump - you might have to
take the pulley off to get to it.
- 10cent
-----------------------

Locations & System Explanation:
http://www.benplace.com/oil_pressure_sender.htm
-----------------------

Testing the Warning Lights/Buzzer:
page 90.24 of the Bentley manual show the test the way I did it to
check the wires, and gauges.

Take the .3 wire off and ground it with the engine running and LED
will flash.

Take the .9 wire off and leave it with engine running above 2000rpm
and the LED will flash and the Buzzer will sound.

http://www.thesamba.com/vw/forum/viewtopic.php?t=324837&highlight=oil+
buzzer

-----------------------

oil pressure relief spring
http://www.thesamba.com/vw/forum/viewtopic.php?t=264817&highlight=happ
y+vanaman

-----------------------
some 2.1L moters were fitted with a 1.8B switch which has a critical switch point of about 20 PSI. If you find a 1.8 bar switch, replace it with a new 0.9B swt (which switches at 10 psi). You can ID the swt as the switch point value is stamped in the side as 0.9B or 1.8B.

-----------------------

low-pressure sensor on the driver’s side of the head - normally closed
and opens at 0.25 bar. The car always pays attention to this sensor
and when this sensor trips the low pressure light comes on. This is
the sensor that turns on the low oil pressure light when you turn the
key to “on” without starting the car. This sensor is not connected to
the oil pressure warning buzzer. It’s typically blue in colour and is
connected to the wiring harness with a blue/black wire

hi-pressure sensor located on the back of the engine, below the pump
pulley??
It is normally open and closes at a fairly high pressure depending on
engine type ( 1.8 bar for gassers??) The car only watches this
sensor when the engine is over 2000 RPM and when this sensor goes off
the oil buzzer will sound and the oil pressure light to flash. It’s
typically white, grey, or black in colour and is connected to the
wiring harness with a yellow wire.

Why the compexity? The idea is that oil pressure that's OK when the
engine is idling is not the same pressure that's OK when you're
roaring down the highway. At idle a pretty low pressure is fine, but
that pressure would be a big problem at highway speeds.

- a flashing light, by itself, is the function of the low pressure
sensor on the head

- a flashing light and buzzer are a function of the high-pressure
sensor

- the car only looks at the high pressure sensor when the car is over
2000 RPM.

Troubleshooting steps:

1) Warm the engine up to full operating temperature (rad fan has
cycled at least once) and then shut the engine off.

2) Turn the key to “on”; the oil pressure warning light should
come on thanks to the lo-pressure sender on the head. If the light
doesn’t come on there’s a problem with the lo-pressure sender, the
wiring to that sender, or the dash cluster. A test light between the
sensor and the positive battery post should light when the car is off
and go out when the car is idling, if the sensor is ok.

3) Start the engine… the oil pressure warning light should go
out. This tells you the engine has oil pressure appropriate for idle.
If the light does not go out you have low-pressure sensor problems or
oil pressure problems: STOP and figure it out before driving away !

4) Slowly rev the engine up to 2500 RPM… the light should stay
out and the buzzer should be quiet. If the buzzer sounds you need to
troubleshoot the hi-pressure system:

a. Disconnect the wire to the hi pressure sensor on the filter
flange and let it dangle. The oil buzzer should now come on above
2000 RPM

b. Now ground the yellow wire and rev the engine past 2000 RPM…
the buzzer should not sound.

c. If you fail either of these tests you have sensor issues, wiring, or cluster issues.

d. A test light between the sensor and the positive battery
terminal should be off at warm idle and come on as you rev the engine,
if the sensor on the flange is working properly. If the buzzer still
sounds with the wire to the sensor grounded the problem is most likely
the wiring to the cluster or the cluster itself.

Sun Mar 21, 2010 9:22 pm

I have read that it could be as simple as using the correct oil filter. It seems some of the standard filters from places such as Autozone or Napa can mess with the pressure switches. Try a filter such as those from Van Cafe, or grab one from a local VW shop/dealership.

Mon Mar 22, 2010 4:18 am

Is the oil high pressure switch replaceable?

Mon Mar 22, 2010 8:06 am

Mconant wrote: Is the oil high pressure switch replaceable?

yes, both low OP and HI Op switches just screw into case.

the are both replaceable.

Mon Mar 22, 2010 8:36 am

[quote="Mconant"]The oil pressure light comes on randomly when i drive, even though I just put in new oil

Since you just put in new oil, did you put in 20W50?

Gary

Mon Mar 22, 2010 8:51 am

I stay away from 20W50 with my stock rebuild as per tencent.
But I always used it in my worn motor.

I use 10-40 now.
The lifters quit much quicker with 10-40

From what I have read, in more cases then not, its your motor, not your oil pressure warning system.

Get a gauge on that sucker and go from there.

Mon Mar 22, 2010 9:58 am

Mconant wrote:
There are three different switches at Autozone. They seem to have different BAR ratings.

0.3 BAR Brown

1.4 BAR. Black

0.9 BAR/ Gray

Hate to be too negative, but in this modern world it's a good idea to learn what "BAR" means.

Thu Jun 02, 2011 9:01 pm

I found this thread very helpful. Thanks, to all who contributed. This is part of what makes The Samba so fantastic.

Randywebb, great information!

Fri Jun 03, 2011 6:56 am

Testing the OP switches is very easy with a test lamp and the engine running and then off. Watch out for the pulleys and belts! Make sure the connection at the plug in the engine compartment is clean too. Even some new OP switches are of poor quality. Find the German ones (NAPA) rather than the China made parts.

If the warning lamp/buzzer comes on intermittently..and is not repeatable...it may be your high OP switch or the wiring back at the engine.

You can check your oil pressure to be sure.

With a worn engine..the low oil pressure problem will be repeatable.

Makes sense to replace the pressure relief spring too. They are getting tired after all these years too. Part number 021.115.421B. Cost is about $5

You can replace the high OP switch that lives beside the crank pulley at the rear of the engine by removing the belts and using a "plummers sleeve socket wrench" from Home Depot if you don't have a regular deep socket, to remove and install a new switch.
Do the pressure relief spring too..you will find the old one is 2-3mm too short and relaxed after over twenty years of operation.

Tue Mar 25, 2025 11:00 am

I couldn’t find anything similar to my current problem so I figured I’d bring back this thread for the time being. I am having similar oil light troubles (on my 2.1) so I figured I should start with replacing the sensors. I managed to get the old low OP switch off after some nudging around (bolt hex size was something truly wonky). Now, when I have tried to install the gowesty replacement, the new OP switch does not want to screw back in. I’ve cleaned the threads of each (although maybe not thoroughly enough) so I’m thinking I might have damaged the female side threads. I attached a photo to this reply. Any advice is appreciated.

Thanks
Jasper

Tue Mar 25, 2025 11:11 am

compare the old to the new. are they the same size tapered thread?

Tue Mar 25, 2025 11:15 am

Yes. The threads are the same gauge as well. This was my original thinking, so I tried to put the old OP back in the same hole it just came out of, but it didn’t want to fit either

Tue Mar 25, 2025 2:07 pm

dabaron wrote: compare the old to the new. are they the same size tapered thread?

Shouldn't be a tapered thread. Stock is 10x1.0 but 1/8" pipe thread is a real close fit so sometimes people shove the wrong switch in there.

Tue Mar 25, 2025 2:30 pm

Altoona wrote: dabaron wrote: compare the old to the new. are they the same size tapered thread?

Shouldn't be a tapered thread. Stock is 10x1.0 but 1/8" pipe thread is a real close fit so sometimes people shove the wrong switch in there.

What would be the best recourse if the old OP was 1/8” pipe thread. I’m thinking this might be the case, since removing the old OP required a socket larger than 24mm

Tue Mar 25, 2025 7:35 pm

Looks like you might have an insert in the hole that might be messed up. :-( Both switches were 10mm tapered pipe thread originally.

Tue Mar 25, 2025 10:32 pm

Read this:

https://brickwerks.co.uk/blog/vw-t3-oil-pressure-switches/

Wed Mar 26, 2025 7:05 am

Wildthings wrote: Looks like you might have an insert in the hole that might be messed up. :-( Both switches were 10mm tapered pipe thread originally.

i'm pretty sure the oil switch ports are M10x1.0 straight thread with a sealing washer required between the sensor body and the block. while a 1/8-27 NPT will fit and seal, i like to use a male M10 > female 1/8 NPT adapter to keep the threads clean.

Wed Mar 26, 2025 8:55 am

lobsterguy wrote: Yes. The threads are the same gauge as well. This was my original thinking, so I tried to put the old OP back in the same hole it just came out of, but it didn’t want to fit either

well it MUST fit... probably an issue of the janky location and not getting it squared to the opening.

i like to turn the threads the opposite direction a 1/4 to 1/2 turn, you will feel it "engage" and then you can turn it the proper way to install...

are you sure you are turning it the proper direction :oops:

Wed Mar 26, 2025 2:03 pm

DanHoug wrote: Wildthings wrote: Looks like you might have an insert in the hole that might be messed up. :-( Both switches were 10mm tapered pipe thread originally.

i'm pretty sure the oil switch ports are M10x1.0 straight thread with a sealing washer required between the sensor body and the block. while a 1/8-27 NPT will fit and seal, i like to use a male M10 > female 1/8 NPT adapter to keep the threads clean.

Yep, definitely straight threads. I would just run a tap through it to clean it up. Maybe coat it in grease to collect any chips that pop off.