Oil light and BIG RED LIGHT

[brian0443]

Help please: I have just had the complete dash out and done some engine work as well. Finally got things together again this afternoon and car started first time. But I am showing the green oil lamp and the big red lamp on the dash is lit. I have an early Mk2. This is the dash layout. (thanks to Stagrinhome Jon for the photo)

I dont think I have an oil pressure problem. When I took the dash apart the earth had been removed from the BIG RED LIGHT. Can someone please tell me what it signifies. Note this model is pre seat belt warning lights.

It may just be a wiring error but could it be that the PDWA is out of kilter.

Thoughts and suggestions before I start to take things apart again.

Thanks

Brian

[nib]

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Hi Brian

At a guess I reckon its your oil pressure switch.

Mark

[brian0443]

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Unclipped contacts from P D W A. Oil light normal. BIG RED LIGHT still on. Is it trying to tell me the PDWA is faulty and/or disconnected?

Brian

[V Mad]

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I am not sure whether you means the green oilwarning light is on when the engine is running (I hope not:shock.

[brian0443]

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Thanks V Mad.

Initial start up Green oil and BIG RED on. Stopped quickly, but no reason to suspect sudden loss of oil pressure. Had read somewhere that PDWA and oil lamp might be connected. Unclipped PDWA connector and restarted. Oil light went out as normal, but the BIG RED LIGHT stayed on. So happy about oil side of things.

WHAT is the big red light supposed to tell me? Is it the early form of PDWA dual circuit warning light?

Brian

[stustag]

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Sound to me like you have a PDWA valve that is out of line or have a fluid leak in your braking system:shock:.

Or a very slim chance the wires are shorting!

Stuart

[brian0443]

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Thanks Stuart

I suppose I am really asking whether the green oil pressure light normally comes on when the PDWA detects a problem.

I can reset it in the next few days to either cure the problem or at least eliminate a prime suspect. Just a little worried that even when the connector is disconnected from the switch this light still comes on. Possible pointing more in the direction of a short?

When I was reassembling the instrument console I noticed that the earth lead for this light was hanging loose, and remade the connection. I was assuming I had knocked it off but perhaps it was a convenient way to put out the light. Braking seems OK and it has passed the MOT braking tests with no problems in the four years I have had it. I'll be looking for a short as well.

Brian

[stagstr]

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brian0443 wrote:

When I took the dash apart the earth had been removed from the BIG RED LIGHT.

Hi Brian,

The wiring around the oil pressure warning light and the big red light (brake line failure light or PDWA light) changed at commission number LD20000. It would be helpful to know your commission number. As a Mk1.5, I think yours will be less than LD20000. ie Mk1.

That said, your quote above appears not be represent either scenario - pre or post LD20000. There should be no earth on the big red bulb according to the wiring diagram. If you've put one on the black/purple wire, then it will be illuminated all the time.

InMk1 (and Mk1.5) form, when the oil pressure warning switch activates due to low pressure then both the green and red lights will be on, but dim. That's because there is 12v across both lights, in series. ie 6v each.

If the PDWA is off centre, for whatever reason, the red light is on bright and the oil warning light is not on at all. As it is normal to knock the PDWA off centre doing routine maintenance, including bleeding the brakes, I always have the connector on the PDWA disconnected. It serves no useful purpose, IMHO.

If you have Mk2 wiring then it looks from the wiring diagram as ifthe handbrake warning light switch would illuminate the big red light as well as the segment in the warning cluster.

Unfortunately I cannot see from either Mk1 or Mk2 wiring diagrams what would illuminate the oil light other than low oil pressure or a faulty oil pressure switch.

Ray

[brian0443]

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Thanks Ray

Well done

There should be no earth on the big red bulb according to the wiring diagram. If you've put one on the black/purple wire, then it will be illuminated all the time.

Thats exactly what I have done, because the trailing lead from the big red is definitely a piece of black wire on mine. I missed the obvious in the circuit diagram. My LD is 24970.

It would appear that there is greater possibility of a link between the two circuits from the Mk 1 diagram but I'll chase that along and see where it leads to. Another MkI feature carried forward to a nominally MkII car.

At least the oil light behaved properly when I disconnected the wiring from the PDWA.

Thanks again

Brian