AUDI A4 SE 2001 Multitronic 41Kmiles, has Oil level low indicator (Orange oil can symbol) ( not Oil pressure = RED oil can) displayed when dip stick says full?
All ideas with regards to the oil level sensor operation (how it works) and its location would be gratefully received.
Thanks
Brian
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Brian,
I have a 2001MY VW 1.9 TDI PD engine, and I suspect the same sensor (or same technolgy) is used on your car.
IF THIS IS THE CASE......The sensor is located in the bottom of the sump, and is held in by 3 screws, and sealed with a retained grooved O-Ring. The sensor is made by Hella, and the bit you can see appears as a pentagonally shaped, cast aluminium, plate. There is an integral connector, with 3 gold plated pins.
It is unlikely that the connector will be giving trouble unless it has been displaced / disturbed by adjacent work.
Techonolgy is thermal - ie the oil needs to be hot before it can sense. See link for more info
tinyurl.com/2ybh6n {Link shortened to www.hella.com as was screwing up the page width - DD.}
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My PD Passat clone has the same sensor. I'm not so sure about the oil having to be hot in order for it to work - I "provoked" it by deliberately underfilling the engine after an oil change and it detected this condition right away.
I think it works by using a series of small thermistors which are electrically heated but cooled by the oil if covered by it. They are probably connected in a bridge configuration so the whole lot tracks for level indiction as the oil heats up - oil overtemperature can be detected by one of the lower thermistors.
An interesting link to the Hella site - two things worry me greatly however. 160 deg C is marginal for a heavily loaded engine in hot conditions with an engine undertray on heat soak. It probably represents the top limit for the active devices in there - they would have been better sited elsewhere. Secondly, there is no indication of its thermal cycling performance - critical in this location. If the packages used are anything like the ones in the pictures, they will be in trouble, even with welded joints.
The joys of complex motoring. I think Mercedes have re-instated the dipstick after making a few models which were totally reliant upon this type of technology.
659.
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Thanks, guys
The sensor only indicates low when the oil has warmed up, thus I suspect the sensor has failed and will need replacing. In the meantime I will keep a close watch on the dipstick.
Will look to replace at next oil change.
Regards
WBD
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