oil pressure light on dash

[gutmeg]

1.9 petrol Holdworth villa 3 1984

HI all hope you all enjoy your bank holiday weekend. I would like some advice please . Van was laid up for winter and just started it  ok, and gone through checks etc for MOT tomorrow, fingers crossed! I have noticed that when keys turned in ignition red battery light only comes on, not the oil pressure light , which always did before. I have removed the dash pod and checked cables etc and all looks ok. I have also checked and cleaned the oil pressure switch underneath. Having put a continuity tester and voltage tester on the switch unit there appears to be no volts when ignition switched on. I have read up and the switch should be normally closed when at rest i.e. key  turned on 1st at idle, and the light should be 'on' as is earthed at rest. This is not the case. I was going to replace the switch but thought I would ask here, as I am not convinced switch is faulty. Could I ask is there supposed to be voltage at the switch all the time when key turned,  and when van running?
Any advice would be appreciated from all.  Any other options for me to look at would help as well. Many thanks and regards. 

[Robsey]

Yes there should be 12 volts going from the fusebox, to the instruments.

Voltage is fed to the led via a resistor, reducing voltage to approx 3.3 volts.
Then through the blue foil back to the oil pressure switch.

Switch is then grounded through the engine block.

If you are not getting any voltage, then you may need to check the connector in the black box in the far left corner of the engine bay.
BUT do not expect 12 volts due to the step-down resistor in the circuit.

Try shorting the wire for the switch to ground.
It should put the led on.
If the led does come on, then it could be the switch.
If the led does not come on, then it is the wiring forward of this.

[gutmeg]

Hi Robsey, Many thanks for the reply re-the oil switch. I will try grounding out the switch to a good earth  as you suggest, and see what happens. I  can replace the cable back to the dash position, if required. When I confirm what colour it is I believe from 1st inspection it  is mauve with red stripe. Thank you for your good advice and options, much appreciated. Have a nice bank holiday weekend. Regards Lloyd

[Robsey]

On early vans, there is only one oil pressure sender for a 0.3 bar switch.
Engine oil light.
This is a blue with black stripe.
----------
Mauve with red stripe.
Not a colour I know of...
Is it not a very dirty yellow with red stripe.?
That would be a coolant gauge temperature sensor wire.
-----------
The nearest to mauve is purple, but the closest sounding colour scheme is purple with black stripe.
This is the fuel tank sender, but does not go anywhere near the engine bay.

(Note - edited to remove potentially confusing 'late' wire colour options).
1984 is early torpedo fuse box electrics.

[gutmeg]

Hi Robsey thanks again for advice I will take a look ref the colurway of the wire. At present pouring with rain where we are so have too wait for a bit! Regards Lloyd

[gutmeg]

Hi Robsey, have just checked the wire to the oii switch, it is definitely a purple with black stripe however there is a connector in the engine compartment and from there to the oil switch it is in brown colour only. I connected a spade on a cable and connector ted to the oil switch , other end I put on earth bolt, and also tried on neg terminal on thew battery. When switching via the key start, 1st turn -no light on lamp in dash pod.  I will put a continuity tester on the cable in the dash pod on the same colour to see if the cable is continuous or not. Thanks for your help. Any suggestions appreciated .Have a good weekend. Regards Lloyd

[Robsey]

Have you changed anything recently, such as the instrument cluster?

The wiring order is different between early and late clusters.

Purple / black is definitely fuel level sender.

Blue / black is oil pressure.

Unless someone has been faffing previously with the wires.

Wiring for T14 plug (Dash Plug) is
(Early 1984 dash).
1 - vacant
2 - brown - earth
3 - grey / blue - instrument lights
4 - blue / white - high beam
5 - brown - earth
6 - yellow / red - coolant temp gauge
7 - red - permanent live for clock
8 - purple / black - fuel gauge sender
9 - black - ignition live
10 - blue / black - 0.3 bar oil pressure switch
11 - glow plug wire (1983 only)
12 - glow plug wire (1982 only)
13 - blue - alternator charge light.
14 - blue / red - indicator terminal

[gutmeg]

Hi Robsey, I have not changed anything on the dash. The van was purchased in 2006 and nothing at all done by me ref dash wiring etc. I am sure the oil light worked previously, although we have not used the van a lot the last few years as Covid etc. Thanks for the dash wiring diagram, very useful, will go through the wiring and maybe rewire the cable if required. 
Many Thanks, and hopefully with the info, I can sort this out to work. If the cable is ok it can only be the oil switch being faulty I guess. Regards LLoyd.

[gutmeg]

Hi Robsey, Many thanks for the info. I have checked the connector at the back of the dash and as you stay all cables/ colours are as stated so all correct there. Many Thanks.
I have put a continuity tester with extended cable, and tested prior to checking the connector and tester buzzes for circuit  so ok there. I have gone through all the connector pins and the only one that  'buzzes' for a circuit is the 'red' cable which is a permanent supply for the clock, which van has not got. The cable to the oil switch is definitely purple /black. I have traced the cable and it goes into the black box left hand side of the engine bay as you stated, and onto the oil switch. I looks like it goes into a relay via. black base in the box which  I cannot seem to access at present.
Can I ask should the oil switch go straight from the dash connector directly to the oil switch. If so could I perhaps pull a cable from dash connector to oil switch directly. I know you stay it goes to oil switch via resistor, where is this in the  black box in engine compartment? 
Any assistance would be greatly appreciated. My next step I guess would be to trace the cables from dash  connector to engine bay for oil switch. Many Thanks, and much appreciated. Regards
Lloyd

[Mocki]

The oil pressure sender wire should not go to the relay in the engine bay box, that should be for the carb manifold heater , triggered by the thermal switch in the metal crossover pipe on the top of the engine .
The oil pressure wire will be brown at the sender changing to blue/black at the main loom, into the cylinder shaped plug and socket iirc

[Robsey]

For clarification of the wiring.

Ignition live feed is the black wire in the cluster connector where it contacts the blue-plastic cluster foil.

The resistor is on the blue foil between the ignition live feed and the red oil pressure LED.

After the LED, the wire re-emerges from the blue foil to meet the blue / black wire in the dash connector.

The blue / black wire goes all the way to the engine bay.
In early vans it may be a single wire connector.
It was in my 1983 van...



In later vans it is a round 7 pin connector.

As stated the blue / black wire can change to brown.
(Just to confuse matters).

[gutmeg]

Hi All, update on thew search for the wire!
I have traced the Blue /Black cable for the oil switch dash light and earthed as suggested, and I now get a light on the dash great.
I have connected back onto the oil switch and no light when switched on 1st turn. progress at least!
The blue / black was initially connected into the cross pipe unit at top of engine which goes to carb It looks like and the purple black was connected onto the  oils switch. This has been like this for many years and the fuel gauger seems to operate ok like this, and I thought the oil switch operated previously ok but maybe not looking at it. I guess if I get a replacement 'blue' oil switch this may do the trick, and connect  the purple/ black onto the sensor on the cross pipe for thew carb this will sort it out. I think what had happened in the past by previous owner/s is that they mixed up the 2 cables as they are right next two each other.  Any options or advice greatly appreciated. Thanks to all who replied and guided me in the right dire lion I feel I am near the remedy. many thanks and Regards.
Lloyd

[Robsey]

Hi Lloyd,

The purple / black is still an anomoly.
It should be the fuel sender wire that should end underneath the cab floor.

The cross-engine pipe thermo-switch wiring should be red to the switch and onward to the manifold heater.

‐-------------------------

I can only assume that a previous owner has carried out some wiring repairs with whatever coloured wire they could find.

[gutmeg]

Hi Robsey, thanks for the reply. I think I seem to have sorted the oil switch problem, which as you say is the Blue/ Black as when earthed the LED oil light came on,  so I think that'll work ok, the switch  must be faulty, as when (purple / black) connected no led is illuminated at all, I have ordered a replacement from Brickwerks. The  purple / Black as I have stated  seems to have been connected to the oil switch  which did not work, and the Blue/ Black connected  to 1 terminal  out of the 2 of the cross pipe sensor. I have tried to look for the fuel sender unit under the van on the petrol  tank to see what colour cable it is (or has been used) as it seems to work ok. Any idea where I can find this sender? side of tank, top, bottom ?
I appreciate your assistance , and help on this, as you seem to know a fair Bit on this topic, if I were nearer I would buy you a beer! Any Thanks and Regards.
Lloyd
 

[Robsey]

If you look under the van there are two main beams - front to back.
Follow the inside-face of the left-hand beam.



When you reach the passenger seat box,
the cable runs towards the centre-line of the van.

On the rear of a metal panel running across the underside of the van floor,
behind another panel running across the van floor that the steering rack is mounted upon...

If that makes sense.

Unfortunately the sender wire is on top of the tank immediately below the floor between the seats.

The photo above is from this thread -
I use it to help me find parts under the van.
This is a syncro, but a lot of parts locations are similar.

https://www.thesamba.com/vw/forum/viewt ... &start=120