oil light

hello everyone ive got a prob i need to no what sender is the right one for the oil light in the dash because when i bought the car it never work and i would like to get it working again . what iam going to do is run a new wire to fuse box for it  . iam not shore sender it is if its the one on cylinder head or if it is the one on top of oil filter  :dontknow:

hi theres, one on the cylinder head and one on the oilfilter housing, as far as i know on my car the cylinder has one and the oil filter hasnt. As i turn ignition it blinks, when i start it up it switches off for a while as soon as i drive faster it blinks, due to no switch on filter.

its both, side of head is 0.3bar filter is 1.8bar. see fusebox sticky for the pin numbers for the oil sensors

im sure the one ontop of the filter head is low pressure the one that activates the buzzer the one in the side of the head is high pressure

nope its the other way round

Found this description of the oil warning system;

The dynamic oil light and buzzer circuit use two sensors to give warning if either of two low pressure conditions exists. The "low rpm" sensor is (usually) located high, i.e., in the end of the head – and the "high rpm" sensor is (usually) located low, i.e., in the oil filter flange.

At "low" rpm, only the Normally Closed (NC) 0.2/0.3 bar sensor (with blue/black 0.5mm wire) in the end of the head is meant to be measured. If more than 0.2/0.3 bar pressure is present, sensor opens internally and light should go out. If less than 0.3 bar pressure is present, sensor reverts to NC/internally earthed and light should be on. Check sensor with ignition on: pull blue/black wire – light should be out. When the wire is earthed to the head, the light should be on.

At "high" rpm, only the Normally Open (NO) 1.8 bar sensor (in petrol/early diesels – 0.9 bar in later diesels, especially TDs) with 0.5mm yellow wire in oil filter flange is meant to be measured. If more than 1.8 bar pressure is present, sensor becomes internally earthed and light/buzzer should not be on. If less than 1.8 bar pressure is measured, sensor reverts to open circuit with no earthing – light and buzzer should come on. Check sensor with engine above "high rpm" threshold: with yellow wire pulled – light and buzzer should come on. With yellow wire earthed to head/block/chassis – light and buzzer should be off.

Important: the two sensors not only have different pressure ratings, but since one is NC and the other is NO, they operate exactly opposite each other. And the result of checking by pulling/earthing wire is opposite. If incorrect sensor is used, it will mess with the circuit logic. In addition, there are 0.3 bar and 0.25 bar NC switches, and 0.9 bar and 1.8 bar NO switches – and probably other specs as well. Sensors usually have the spec stamped in one of the flats of the hex.

On petrol engines, "high rpm" is ~2000 rpm and above, and is measured by the intermittent earthing signal from the coil terminal #1, which also drives the tach.

On at least some diesel engines, "high rpm" is measured by signal from the "W" terminal on the alternator – I don't know what the diesel rpm spec is. Some diesel schemes may be different.

Permanently earthing the yellow wire from the "high rpm" sensor in the filter flange should permanently defeat getting a low oil pressure warning at "high rpm", just as permanently leaving disconnected the blue/black wire from low rpm sensor at end of head will permanently defeat getting a low oil pressure warning at less than "high rpm". But I don't suggest defeating them – they are there for a reason!

I do not know what happens if the oil buzzer cicuit does not get a "high rpm" signal from coil or "W" terminal of alternator. Probably the "high rpm" warning would never come into play, as the warning circuit would "think" there is zero rpm.  If a break develops in the circuit from coil or "W" terminal, and the clocks/cluster side of that wire (or trace) then becomes permanently earthed, the circuit logic may read that as permanent "high rpm", giving a buzzer at less than ~2000 rpm.

The L-shaped low pressure light/buzzer circuit boards in the clock/cluster are known to give trouble. If buzzer comes on all the time, not just at "high rpm", it usually means a bad circuit board. Permanently removing it will defeat both "high rpm" and low rpm warnings, leaving you with no protection. It should be fairly easy to recover the low rpm warning light by jumpering (bridging) 2 of the 6 slots that the circuit board was plugged into. I don't know how, or if, they are identified in the cluster – they may be labeled "0.3" and "A" .

its worth noting also that earlier cars such as the MK1 have the 2 wire colours switched, so high pressure gets blue wire and low gets yellow

yea not sure why the colours are switched in stuff I copied from the net (came from the Caddy forum, Caddys are MK1 based and it talks about 'early' diesels?)

Just been out into garage and checked mine.

The '83 1.8 GTi has yellow wire to a brown switch in the head and a blue/black wire to combined VDO oil pressure sender in the filter mounting.

The '87 Cabrio 1.8 Carb has the same but the filter mount switch is the normal white switch rather than a VDO sender for auxilary guages.