Help needed. Engine wiring, oil pressure circuit

[dalla]

Hi RTOC,

Run into some problems with my R5 GTT i was hoping you could help me with. My instrument cluster isn’t working quite as supposed and I’m a bit stuck regarding reading of the diagrams.

Problem with oil level/pressure gauge:
- With ignition ON:
Oil light lights op but oil level gauge stays dead and doesn’t show any level.
- With engine running:
Oil pressure gauge stays dead – no movement at all.

As I understand the system it should show the oil level when ignition ON and switch to oil pressure once started.
Looking at the wire loom in engine bay there is 2 wires going to the pressure sensor (Orange and Brown)
Also 2 wires going to oil level sensor in tub, which also are Orange and Brown.

The wires have been traced back to instrument through a big connection point behind left head light (which were pretty corroded)

Have tried to “short circuit” the 2 wires going to the oil level sensor in the pan as I thought that would trigger instrument needle to show “full” but still no movement.

Removing the 2 wires from the pressure sensor switches off the oil control light.

Attached are 2 diagrams – 1 for Oil pressure gauge (dual purpose) and 1 for screen wash.

Can anyone explain what the symbols are fore? (marked with pen)

Hope you can help me

Regards Dennis.

[Mad_Mat]

My oil level/pressure gauge was working intermittantly.
In my case it was the level sensor just needing a clean up.
It would seem that if it does not read a level 1st it will not switch to pressure once running and the needle remains static at the bottom of the gauge.
MM

[Ian S]

At the bottom right of the diagram id says in the box that '57' means 'link bar'. But the right had drive models have a 'wire join' there instead.

My oil pressure stopped showing oil level but pressure worked as normal.

This probably won't be much help but I very vaguely recall someone saying something about earthing one of the wires at the sensor would operate one of the gauges.

[Matt Cole]

Im not sure on the symbols maybe a resistor? Ian isn't this your bag being electronic?

[dalla]

Hello guys,

Thanks for the advice given, I have been looking abit more into the problem, and according to the wiring diagram both wires to the oil pressure sensor should be coming with 12v to the sensor.
1 wire for oil pressure lamp
1 wire for oil pressure gauge
When measured i only got 12v on the wire going from pin connection 2 (orange wire) to oil lamp.

Reading the diagram there is a 12v supply coming in on pin connection 3 on the back of the instrument connection bar, this supply is then split up into 2 where one wire is to lamp and the other to gauge.

I have tested the oil pressure gauge (coil) itself by connection 12v and it gives a full read out so problem is somewhere on the back of the print attached to the instrument panel as i can't measure any connection (resistance) between pin 3 and pin 9.. investigation ongoing :-)

regards Dennis.

Ps does anyone have the wiring diagram for the oil level sensor? can only find the one for pressure?

[Matt Cole]

This is good info Dennis as I need to check the gauges work on mine both oil and water temp.

I'm also wondering can the oil pressure gauge work with an aftermarket sender? I don't want to use an ancient gt one.

[dalla]

This is good info Dennis as I need to check the gauges work on mine both oil and water temp.

I'm also wondering can the oil pressure gauge work with an aftermarket sender? I don't want to use an ancient gt one.

To test the gauges them self you just disconnect the socket (e.g water temp by water pump) and connect a test light to the pin of the socket and other end of test light you connect to earth. if gauge working it will give full reading in instrument..

would think a aftermarked gauge would function on same parameters but would have to get the specs of the aftermarked gauge in question.

regards Dennis.

[Matt Cole]

Thanks Dennis.

I guess the resistance of the sender would need to match the parameters of the gauge? Im not sure as im not really up to speed with electronics.

[dalla]

Thanks Dennis.

I guess the resistance of the sender would need to match the parameters of the gauge? Im not sure as im not really up to speed with electronics.

Hi Matt
If you just want to test functionality of gauge you dont need to worry about that - by leading it to earth through the test light the gauge will just give full reading on the gauge - no harm in that.

regards Dennis.

[Matt Cole]

Spot on matey. Going to give it a go.

[dalla]

Spot on matey. Going to give it a go.

you welcome :-)

just get a hand from a friend so 1 sits in the car and 1 connect the pin to earth, you just need to see needle move between 0 and 100% (meaning dont leave wire connected to earth longere than needed)

btw you will have 2 wires on each sensor - when leading 1 to earth it will light up the warning light (water temp or oil can) and the other will function the gauge (so it dosent matter which one you test first)

regards Dennis.

[dalla]

Hi guys
I think that I have traced the issue to the print card behind the rev counter.
It seems that this does give a supply to the oil pressure gauge.
It looks like this.



Any idea how to source a new one? If anyone has an old speedo they want to sell, I'd be interested.
Only thing is, I don't know how big the difference is between LHD and RHD speedos.
My car is LHD.

[Ian S]

Have you cleaned all the electrical contacts?

I presume you have a multimeter, have you traced the voltages on the tracks and components?

I would measure all the resistors to see if they are still conducting and then take out the capacitors and measure them. Replace if needed.

[dalla]

Have you cleaned all the electrical contacts?

I presume you have a multimeter, have you traced the voltages on the tracks and components?

I would measure all the resistors to see if they are still conducting and then take out the capacitors and measure them. Replace if needed.

Yeah have done that. I have determined that the print board foil thing on the back of the speedo is working.
However I have also determined that the oil pressure gauge doesn't get any 12V supply. Seems like the circuit goes through this print board. So I suspect that this is causing it. However i cannot pinpoint it further. I have measured at resistors, and they seem to be working..

[Ian S]

Maybe that chip is still available, all the other parts can probably be replaced at low cost.

If it's just oxidation of a contact, or a broken solder join, it would be best to put that right first than changing parts first.

[Matt Cole]

I didn't even know all that is in there!

[dalla]

I sourced a new speedo from the Netherlands. Supposedly working when it was removed from the car.

[Matt Cole]

Let us know how you get on boss. If you repair your old set would be a good article for all!