oil pressure light and buzzer problem

this problem started after car laid up in dry storage but run for 30-40 minutes eevry month.  i have changed fuse box, dash clocks, low pressure sensor, 2 pole sender for high pressure and auxillary oil guage.  have changed oil pump and oil to 50-40 SAE

Oil pressure 2 bar (warm)at 1000 rpm, 4 + bar at 2000rpm, buzzer and flashing oil light after 2000 rmp disconected red dash black wire in to rear of dash clocks now no buzzer or tacho. when bridged wire with test lamp to earth increased in brightness as revs increased. oil p[ressure light sometimes flashes when ignition turned on for a few seconds.

anybody know the problem and how to solve

thanks 

Have you validated mechanically that you don't have a pressure issue?

That would be my next step.

see:
Dynamic Oil Pressure System Operation

and

VinceWaldon.com - Stuff I Think is Cool

If you have tested it with a mechanical gauge then you may have a bad sensor mech in the Cluster.  One of the issue that I have seen over the years, is that the cluster connections get iffy.

Here is the light and Buzzer pcb mounted inside the Speedo.






It is in the back of the speedo housing, that is you have to remove the cluster to replace it.

Why they put it there IDon'tKNOW.

Now ensuring that you have good power and ground to the cluster is paramount, that is usually pin 2 Brown for ground, and pin 14 Black for +12V.

You can remove the Mylar connections shroud, carefully remove the mylar off the tongue of the housing, then place a single strip of electrical tape on the pad side of the tongue. Replace the mylar, and the shroud.  This will tighten up the connections.



Find the ground wire on the harness and about 6 inches back you can use a Scotch-Loc wire splicer and add a 7 inch wire to that.  The other end gets a ring connector and you drill a pilot hole between the "X" of the cluster mount and scuff the paint around the hole and attach the ring connector with a self drilling Sheet metal screw.





This will give you a solid ground to the cluster.

If you are using a non-brand, generic, storebranded filter,  Bosch or Frame, throw them away and get a WIX, PureolatorGold, Mann, Mahl, STP, Mobile1, or Genuine VW filter.  Store Brand, Generic, and Bosch are known to cause flaky pressure problems and flow issues.
 

Thanks very much

I have replaced dash clocks with a good set, changed 2 pole oil sensor on top of oil filter housing and earthed brown cable from rear of dash as advised - unfortunately  there's still a problem.

Well the light flashes at ignition on as the oil pressure hasn't built up.

You state that above 2000K the buzzer and light flashes, as that indicates low oil pressure at hi-rpm, so I would have to ask what the pressure is…. as rule of thumb 1 bar per 1000 rpm when hot.
SAE 40-50…..

Do you mean 10w40 or 20w50, as I have never heard of 40-50.  Is it a Synthetic Blend or Old Timey Dino oil.

Have you replaced the engine/tranny to frame ground, and is your Valve cover grounded to the Coil bracket?

Otherwise you are going to need mechanical verification of working pressures as something is tripping your HIGH RPM low oil pressure switch and that is usually oil pressure.  If your oil pump new ( was bad) there is the possibility that your bypass is stuck open or fluttering as it thinks the oil pressure is too high so it opens to relieve pressure, I have also seen (been there) that some of the Oil pressure switches aren't rated the same, and can also be bad out of the box.  This is why I am telling you to have the Oil pressure mechanically tested…

Also that some of the newer low pressure/oil pressure sender cans are suspect from the get go.
I also know that the 13 dollar ones from ebay, are POS's and that you have to spend about 60-100 to get the ones designed for VW, and that they have the correct BAR settings from a VW vendor and not ALIBABA (Chinese).



 

10w40 semi synthetic oil is what you want if you are in the UK.

AVS Car Parts

https://www.eurocarparts.com/ecp/p/car-parts/engine-parts/engine-parts1/engine-oils/?521776011&1&cc5_245

What brand of oil filter have you used, geuine VW or MANN filters are the ones to get.

https://www.vwspares.co.uk/product_info.php?products_id=1179

https://www.eurocarparts.com/ecp/c/Volkswagen_Golf+Cabriolet_1.8_1989/p/car-parts/regular-service/car-service-parts/oil-filter/?501770059&1&df2e88f773d5c865f404b9dd795cf6fb0b433883&000231

As Briano1234 says check there is a earth lead from the back right hand side of the rocker cover to the coil bracket as that can cause also sorts of strange problems with the instruments.

Although infamous for false alarms, you've checked or changed almost everything so I'd check with a pressure gauge that there is some pressure and the engines not really dying.