Oil pressure gauge

[stevemac2002]

I am trying to work out why my gauge has started reading 5+ all the time and I think the blue/white wire is broken somewhere in the loom under the engine. Does anyone know what the resistance to earth should be on this wire from the sender end? Also where is "T21 Connection DME" located? From the cct diagram it appears this is where this wire terminates and I could buzz it out from there.

 

[homesea]

Sorry cant help but mine is doing the same!! Started last week when we had a lot of rain and I drove through lots of deep water. I was just going to by a new sender but at £85 from OPC its a lot so would like to know if a wire has come off 1st.(might have a look next week). If it is off the top of the gauge will that be open circuit or short circuit?

 

[edh]

Sender is much cheaper from GSF (IRO £40) Not sure how to test - Clarks Garage is normally the place to start

 

[James_G]

ORIGINAL: homesea Sorry cant help but mine is doing the same!!  Started last week when we had a lot of rain and I drove through lots of deep water. I was just going to by a new sender but at £85 from OPC its a lot so would like to know if a wire has come off 1st.(might have a look next week). If it is off the top of the gauge will that be open circuit or short circuit?

The guage will read to 5 when open circuit. I had this recently, and one of the leads had come off. I had the wheel off at the time and it took literally five seconds to put it back on again. Et voila, back working.

 

[Diver944]

Mine died last summer, it fails open circuit and reads 5 bar as soon as the ignition is on. New one was £28 plus vat and postage from Type911.co.uk http://www.type911shop.co.uk/shop/article_861/944-all-Oil-Pressure-Sending-Unit.html?shop_param=cid%3D1%26aid%3D861%26

 

[stevemac2002]

I don't think its the sender as a new one was fitted only a couple of 100 miles ago. I have also measured the resistance of the sender and it seems OK measuring around 10 ohms with engine off and rising with engine on. 12v appears on the blue wire with ignition on so I guess the current must go through the sender and down the blue/white wire to earth or earth via the gauge. This is where I am stumped as the blue/white wire is open circuit to earth. I guess this wire is broken somewhere but I don't know where it goes to so I cant test it unless I remove the dash which I dont really want to do if I can buzz the wire out in the engine bay. Does anyone know the route this wire takes? Is it part of the loom that emerges from behind the cam belt casing at the front of the engine..its so hard to see [8|]

 

[Mike_Pollock]

Hi The wire comes through the bulkhead in the large bunch that includes all the engine management wires. They are routed over the top of the engine and originally down between the front of the block and the belt cover (they often get replaced over the belt cover as it is almost impossible to rethread!). My guess would be a break by the connector under the boot on the switch, or between the switch and the top of the engine. Good luck Mike

 

[stevemac2002]

Found the break in the blue/white wire.. in the loom behind the belt cover!! I had to cut through the sheath and pull back the wire, then had to splice in new wire and re-thread back behind the belt cover down to the sender. Pressure reading Ok now except there a new problem has emerged. The "Engine Oil" warning is on all the time together with the master alarm light. Does the signal for this alarm originate from the same sender as the pressure reading?. I am assuming its the blue wire from the large spade connector on the oil pressure sender. However,this does have 12v appearing on it with the ignition on and the sender is short to earth with engine off and then goes to Open circuit as soon as the engine starts and oil pressure rises. To my mind this is then working OK. Is there any other sender that can drive the "engine Oil" warning light? like an oil level sender for instance.

 

[homesea]

Some 944, I think post 87 had oil level senders in the sump. I am nearly 100% its a different wire for it. My old Lux used to come on if the oil was just off the top of the dip stick. Maybe check your oil level 1st.[]

 

[stevemac2002]

Oil level is OK and light has now gone out after a couple of starts and a quick drive around the block. I am guessing ( if there is a level sender) the oil may have drained out of it with the car jacked up high on one side while I was fixing the broken sender wire. So fingers crossed my original problem is fixed (new blue/white wire to sender) gauge now reads just under 5 at start up and drops to 2-3 when hot on idle, engine oil warning is off and the sun has just come out so its roof down and off for a spin.