Oil Pressure sender issues

Hi, I am newcomer to the Club but have owned Mk1 Scirocco & Golfs since 1985. My pride & joy is a 1983 Black 1800 Golf GTI Mk1 which I have owned for the last 22 years, originally as a daily driver but now a weekend car which I regularly show (YMV578Y). I do all my own servicing and try to keep my Golf stock as possible but with some period extras.

My problem is this - I have fitted VDO Oil Temperature, Oil Pressure and Voltmeter gauges with all the correct senders (a T piece into the oil filter housing for the low oil pressure switch and new temperature sender and a 0-10 Bar dual pole pressure sender into the head) and whilst the voltmeter, dash oil lights and oil tempertaure gauge all work fine, I am having problems getting the oil pressure gauge to work.

The original VDO Oil pressure sender and gauge worked briefly but the 'G' gauge pole voltage dropped to zero and the gauge maxed out. I replaced with an alternative make sender and this also doesn't seem to want to play either. I know it's not the gauge as I have 2 and both give the same max reading (needle off the scale) and both are 0-10 Bar. When I put a meter across the 2 poles, the high pressure switch gives out c.12V and the 'G' gauge gives out 11.8V irrespective of engine revs.

I have tried to establish what voltage the sender should be putting out and my understanding is that it should be nearer 0-5V for the gauge to work. Can anyone please help me here because this is driving me mad ? Do I need to replace the sender for a 3rd time (both were new). I have naturally wired the gauge correctly being an Ignition live, Earth, Sender and dimmible Instrument light feed.

Please help me here. Thanks Jeff

Hi Jeff and welcome. 22 years with a Mk1, well done.

From your description sounds like you've done everything OK.

A couple of thoughts off top of my head; (not trying to teach you to suck eggs etc)

With a cold engine the gauge will show max pressure even at idle. Does it still do that with a hot engine?

Not sure measuring volts between the poles of the sender/warning switch would give any useful info?

My understanding is that the guage will show max if there is no sender attached, double and triple check the same wires goes from G on the sender to G on the guage, that the wire is intact with good connectors and not shorting to earth anywhere.

The sender needs to be earthed to the block via the screw thread, have you used PTFE tape to stop leaks and so insulated the sender?