Club 80-90 Forums

Firstly... I know it's been covered in other threads, and other sites... but I'm still uncertain

My engine is an '84 DG. It only has the one oil pressure switch (low pressure) at the bottom, in-between the pushrods.

From what I've read and understood... the oil light should come on with the ignition (low pressure, switch should connect to Earth), then go out when the engine starts (high pressure, open circuit).

The light doesn't come on at all when the ignition is on, this indicates an open circuit. I've taken the wire off the oil pressure switch, and connected it to Earth. The oil light then lights up. This proves that all wiring, dash, lamp etc is working fine, therefore I'm pretty certain that the switch is knackered and causing a permanent open circuit?

The switch is black in colour.

Just had a look on JK, VWH, Brickwerks etc, they all seem to sell 4 different types at different pressures:

Black: 1.2-1.4 bar (not exactly "low" pressure)
Blue: 0.15-0.35 bar
Grey: 0.75-1.05 bar
White: 1.6-2 bar

I've read somewhere to use a blue switch for low pressure? Is anybody able to confirm this? As the original colour I assume doesn't correspond to modern replacements? Is there anyway of telling what the actual rating is of the old one? (It's really rusty, can't see a part number or anything on it...)

Also read on Brickwerks that the Blue is the only "normally closed"... the rest are normally open. Is the "normal" position with the engine off or running (i.e. low pressure or high pressure)

Many thanks for any advice


E D I T: Forgot to mention, the cable that goes to the switch is brown in colour, and has a plastic connector near top of engine, then I its a blue wire (I think it has a black trace) that goes into the junction box... if this refers to a certain pressure switch??

"Also read on Brickwerks that the Blue is the only "normally closed"... the rest are normally open. Is the "normal" position with the engine off or running (i.e. low pressure or high pressure)"

Normally closed is when no pressure/voltage or whatever is applied to change the state of a switch.
I presume that you need the blue one - but I don't know petrol engines so wait for confirmation from someone in the know.

I've just been through this myself with my 86 1.9 DG trying to get a new high pressure switch. I could'nt get a straight answer anywhere ... Brickwerks said "its probably a grey but there's no way to be sure". Eh?


Mine had two sensors, brown on the bottom, and I went for grey up top. Replacing that badboy was chuffing nightmare

If you only have the one switch between pushrods yes you want blue
Black grey and white are all for the dop or buzzer of doom which if fitted is at rhe back under the waterpump

Blue is normally closed with no oil pressure and open circuit when it has oil pressure
The other colours are the other way around
Id agree with your fault finding theory change the switch just be careful not to damage the pushrod tubes as its hard to get any sort of spanner on

Highly reccomend you get a good quality switch from brickwerks not worth risking a cheapo

Col.decker my 88 dg high pressure switch is grey by the waterpump and blue by the pushrods you could fit the black or white if you like in place of grey as they are higher pressure but you may get some false triggering of the buzzer

The high pressure one by the water pump that I took out was a Black one. Changed it because I was getting the buzzer of doom (all the time). Since I changed the switch the buzzer hasn't gone off

Thanks for all the info guys

I also had a look through the Haynes manual last night, which says the low pressure switch should operate at 0.3 bar +/- 0.15... which too indicates that the blue switch is the right one

Just ordered a blue one from Brickwerks... now my only problem is getting the old rusty one off I've been spraying it with a bit of WD over the past couple of days, hoping that it's some help . Now just to borrow a deep 24mm socket, as my standard socket isn't long enough... spade pokes out of the back preventing me from fitting ratchet handle

Errrrr.... break the spade off or fold it over? You are replacing it anyway! Or have you a shovel in your engine?

Still need to tighten the new one^^

That's where you delve into the bottom of the tool chest and dig out those old box spanners.

Had a good look around yesterday but nothing the right size

I'll pop into Halfrauds and get a deep socket, only £7.49, minus trade discount

I just have visions of the old sensor snapping off and leaving the M10 thread inside the engine

See pic... really rusty

richlaz wrote:really rusty

At least it isn't leaking... <grin>

Box spanner 30 - 40p to me it's a no brainer!

Except you cant fit a torque wrench to a box spanner

I can - why can't you?

itchyfeet wrote:Except you cant fit a torque wrench to a box spanner

I don't think torque's particularly critical. A half-decent nip up, without swinging off it.