Sigma Danfoss Oil Pressure Sender - where do I get one from?

[ChrisC]

Yer but that is "not" the part fitted to the Caterham Sigma engine.    I am guessing that switch is swapped out by Caterham and replaced with the Danfoss pressure sensor because the Caterham has a oil pressure guage not just a light. 

I think this a call to Caterham parts, and brace for the price. 

Saying that, Caterham Sigma parts prices are not alway that bad.   They where only £1 more expensive for a single No.2 ignition lead, and they had that in stock, unlike my load Ford dealer, and when I upgraded to the 150 kit, the blue injectors where £10 cheaper each than Ford dealer supplied parts. 

[Iain McCallum]

Thanks for all the suggestions guys. I have actually sourced one from Redline for £65 plus VAT. They didn't know they had one, but found it during a stock check this week! It is actually labeled up for a Duratec in their description.

Will be fitting it this weekend to see if I get my oil pressure back!

Thanks Iain

[Martin J]

Interesting info as I have the sigma engine. Did you test the gauge by grounding the feed to the sensor & seeing if the gauge went full scale?

[Jonathan Kay]

Martin: Do you have access to Danfoss parts that's better than the source I found online?

Thanks

Jonathan

[Iain McCallum]

Oil pressure update time!

I looked at replacing the actual unit but found that I didn't need to. It turns out that the other end of the existing cable connector came undone VERY easily from the pre-existing supplied wiring. I plugged it back in properly and placed it on top of the chassis bar it was tied to (previously underneath) and now I have proper oil pressure readings (fluctuating nicely with revs).

I would have expected the gauge to not read anything at all in this disconnected situation i.e. 0 but it was still reading something. I know the gauge takes feed from the rev counter but where is it getting this feed from - an ECU output?

Slightly baffling but not a problem anymore!

Note to self - check ALL connections before shelling out for replacement parts! At least I now have a new spare sender unit!

Many thanks for your help

Iain

 

[Jonathan Kay]

Glad it's solved.

I would have expected the gauge to not read anything at all in this disconnected situation i.e. 0 but it was still reading something. I know the gauge takes feed from the rev counter but where is it getting this feed from - an ECU output?

The gauge might have enough damping to tide the display over for a bit. But yours is fluctuating nicely... What does it read now if you disconnect while running, and how quickly does it drop?

Have you got a wiring diagram already?

Jonathan

[Iain McCallum]

Jonathan

Just got the engine up to operating temperature on idle and the oil pressure read about 2 bar and increased to approx 4 bar with throttle.

While it was idling I disconnected the lead from the sender and the gauge initially went full scale and then dropped to about the 2 bar mark very quickly. I left it idling for about 10 mins and it still read 2 bar with no change on throttle application - as previously seen - so this led to my thinking that the sender was at fault.

Connected up the sender lead again and everything is reporting correctly.

Very strange!

It is a standard Sigma 150 so the current wiring diagram will be valid but I am rubbish at reading them!

Cheers

Iain

[Jonathan Kay]

Fascinating, thanks.

So the not dropping to zero is not caused by damping in the gauge. Which leaves... internal snubbing in the sensor. I'm now way out of my depth, but could the experts advise if that could cause that effect if it was the feed that had an intermittent fault at the connector?

Jonathan

[revilla]

Reading the data sheet for a similar Danfoss sender here:

http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/04/IC.PD.P21.H3.02.pdf

It appears that the sender contains active electronics; it takes an external power supply (8-30V) and provides a direct voltage output (1-6V) rather than being a simply variable resistance. With the sender disconnected the gauge may well just float to a mid voltage position, rather than dropping away to the high resistance end as it would with a passive resistive sender. The sender appears to have at least a limited capacity to drive loads returned to the supply or ground, so will be capable of pulling the gauge either way from its floating central position.

As described on Page 2 of that document, the optional "Pulse Snubber" within the sender is actually a mechanical device  It looks like a restricted orifice with a cavity behind it slowing down the response time to rapid pulses (it's actually a direct mechanical analogue of the electrical snubber you linked to Jonathan where the restricted orifice represents the resistance and the cavity the capacitance). It won't be affecting the electrical characteristics.

I suspect the initial "kick" to one end was probably caused by the pins of the connector not disconnecting at exactly the same time; for example if the power supply to the sender disconnected first it would pull the output to ground briefly.

I found this Workshop Manual:

http://workshop-manuals.com/ford/focus_2004.75_07.2004/mechanical_repairs/3_powertrain/303_engine/303-01b_engine_1.6l_duratec-16v_ti-vct_(sigma)/specifications/

This is for the Sigma Ti-VCT variant in the Focus but I'm guessing oil pressure specifications will be similar (I'm a K Series man so not too sure about the Sigma variants). This talks of a minimum hot oil pressure of 1 bar at 800rpm and 2.5bar at 2000rpm with pressure relief valve opening at 4bar, so your readings sound quite healthy.

With the engine stopped but the ignition on, does the pressure reading on the gauge drop to zero?

If so, sounds like you are now good to go and it was the loose connector to blame for your issues.

[Jonathan Kay]

:-)

"Knowledge is of two kinds. We know a subject ourselves, or we know where we can find information upon it."

Jonathan

[Iain McCallum]

An excellent insight. thanks.

The full scale was probably due to the pin disconnection as you suggested, because it only happened once. The other times I disconnected, it went straight to the 2 bar position.

The slightly confusing thing, still, is that there is variance in the gauge when it is disconnected from the sender. To me it was like the gauge was sensing a temperature reading, because it did rise up dramatically as the engine got really hot.

However, I am now happy that i didn't have to replace the sender to get it fixed!