VW Golf Mk2 Owners Club

Is it a 10 bar sender and your gauge is to 5 Bar?

If it's possible, go back to your FAE sender, it was 5 Bar and fit it at the point above the oil filter to see what readings you get.

Different engines I know, but to give you an idea - The 205 has a factory 5 Bar gauge and is on its original sender so presumably 5 Bar compatible and giving as accurate a reading as factory gauges will allow.

At idle on cold start up it will be showing around the 4.5 Bar mark before eventually dropping to around 1.5 Bar when fully warm.

If you look at the specs for senders on the VDO webhop site it'll show the measurement ranges for 5 and 10 Bar senders which'll give you an idea of the differences.

If I've understood correctly they work by using resistance, measured in Ohms.

Most VDO gauges seem to work between 10 Ohms and 184 Ohms... if you're using a non-VDO sender with a VDO gauge you'll have to ensure it works between this same range.

Below is listed the 5 Bar senders ohms readings beside the 10 Bars - it'll show how using the wrong sender / gauge combination can affect the gauges accuracy.

Oil pressure is 0.0 Bar

11 + 10

Oil pressure is 1.0 Bar

47 + 31

Oil pressure is 2.0 Bar

82 + 52

Oil pressure is 3.0 Bar

117 + 71

Oil pressure is 4.0 Bar

151 + 90

Oil pressure is 5.0 Bar

184 + 107

The 10 Bar sender will continue in 1 Bar increments to its max as follows -

6 Bar 124
7 Bar 140
8 Bar 156
9 Bar 163
10 Bar 184

If your engines true oil pressure is 3 Bar your 10 Bar sender is giving the gauge a measurement of  71 ohms instead of the 117 ohms a 5 Bar sender would be so it'll be under reading by about 40%.

You've got the pressure sender in the wrong place really.
You should try and get it on the oil filter housing, as that is the closest you'll get to the pump.

When it is mounted there, you should see around a bar at idle, once fully warmed up.
So with it mounted in the head, I'd say you weren't too far wrong, seeing the head is quote a way away from the pump.