Buzzing / squealing sound

Hello guys need some help after trying to sort my vdo gauges out, and wiring them correctly, the temp goes to 150 and the oil bar is on 0, but after driving it for a short while there is a buzzing / squeal sound same as tje one you get from tbe buzzer when oil pressure is low but the oil light isn't flashing on dash, I did unplug the wire from the high oil pressure switch on top of the oil housing and drive the car for then the oil light to flash and the buzzer to sound, I re connected the wire and all well, I did around an hour of driving from 30 moh to 60 mph and even on a dual carriage way at 70mph, all was well I then went out again this evening for the buzzer to sound again but this time I carried on driving and the buzzer went away I switched the car of for about 5 to 10 minutes and then started it and drove off again, there was no sound this time, I can't get my head round what it could be I have now disconnected the temp gauge  and oil bar gauge wire, to take the gauges out the equation as it all happened since I been working on tbe gauges, I did also ground the high oil pressure switch wire so unsure if that  made the switch go bad, but as me mentioned when the wire is off the switch it does light up and buzz so the switch must be working OK, all help is greatly appriciated just want to get to tbe bottom of all the buzzing / squeal, thank you

The oil pressure warning curcuit 'L' board is known to play up so it may just be its decide to do it at the same time has your wiring mods.

Have you put back all the factory wires? Not sure from your description if you are trying to use some of the existing pressure switches/wiring for your guages?

Early-1800 said

The oil pressure warning curcuit 'L' board is known to play up so it may just be its decide to do it at the same time has your wiring mods.

Have you put back all the factory wires? Not sure from your description if you are trying to use some of the existing pressure switches/wiring for your guages?

It's a 1.6 GTI 1982, the wiring was already there but not in the correct order ie: like I'm the connector the positive was in the pin that was mean to be where the wiring for the sender was ment to go so all over the place, but even after attaching it to the correct pins the oil temp shot up to 150 degrees and the oil bar is sitting on 0 , so now I removed the green and black wire for the oil temp pin but the need still shot up to 150 so now I have disconnected that gauge plug , and also removed the oil bar sensor wire on the oil bar gauge , I will take the car for a drive and see if anything changes, also is it possible to buy the 'L' board separately , just surprised how it buzzes and then it went away and comes back and without any oil light flashing,

Sent from my SM-J510FN using Tapatalk

Sorry I'm still not sure what you are connecting to what.

Are you using any factory wiring in the gauge ciruits?

A S2 '81 1.6 didn't have MFA or S1 gauges so your gauges would need new additional seperate wiring from whats in the factory loom.

If your gauges are showing 0 or full deflection straight away your senders are U/S or you are connecting to pressure switches not gauge senders?

The only link from the exiting oil pressure warning circuit is one of the 2 warning switch wires would be connected to the 'tophat/can' pressure sender if it replaced the loction/switch used but the original pressure switch.

If it was me I'd reconnect to the original factory spec and see if that stops the flashing/warning.

EDIT- note the warning curcuit is over complicated (its a german car), instead of a switch, a wire and light it has 2 switches which operate at different pressures. One is open then closed and the other closed and then open. It also uses rpm from the coil and a buzzer as well as a light. Its easy over the years for the switches or wires to get mixed up or switches replaced with wrong pressures or open/closed closed/open. Also make sure the brown earth wire on top of the camcover is present as this can casue dash cluster issues

From else where on the internet ;
white on filter housing is high pressure switch for buzzer & light over 2kish if pressure is bellow 1.8bar, side of head is low pressure switch and triggers light at idle if pressure goes below 0.3 barearly mk1s have blue wire to high pressure sensor and yellow to low, later cars have these wire colours switched