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Oil pressure light comes on at low RPMs- Plenty of oil. Before I start chasing parts......

Bomb Factory

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1996 S4S

Runs like a top.

Notice that my pressure warning light comes on at low RPMs.  

Plenty of oil.  

Was planning on just replacing the sender (same as pressure switch?) but I was reading on some other posts that it could be just the light.

Im about to replace my boost gauge with an updated VDO that has more range and also vac.

While Im in there wondering if there is a way to test the oil pressure light to be sure that is not the issue.

I see a transducer listed on a dealer parts site - see below for PN.  But it is $317 and I dont want to just throw parts at the problem.  Any experienced advice is appreciated.

I dont believe there is a real issue with the pressure but it is very unsettling none the less to see the light come on knowing the criticality of proper oil flow.

Plus literally everything else on the car works (I hate to even mention this fact because it is tempting the universe to blow something on the car up) and I want to get this issue sorted.




Part Number: A082N4038F





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Since it is never good to assume:


You running 15W or 20W-50 oil?


Did you find this Topic?


Plenty of suggestions on LotusTalk, too.


SEARCH oil light flickers at low RPM

Atwell Haines

'88 Esprit

Succasunna, NJ USA

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  • Gold FFM

Have you checked the low rpm oil pressure relay hasn't failed? That could cause the symptom you describe. Should be relay B in the rear relay station in the boot/trunk.

$317 for an oil pressure transducer, what is it made of :o  SJ Sports Cars have them listed for £55, even with US Shipping that's significantly cheaper if you end up needing one. But I'd start with the cheap/simple relay first.

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Norfolk Mustard S4s #1 :)

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  • Gold FFM

Having thought about it a bit more, the oil pressure transducer is nothing to do with the low pressure light on the S4s. The change to the Caerbont gauges in the S4s resulted in the oil temperature gauge being deleted and there was a separate low pressure swtich and oil pressure transducer used instead of the combined unit in the earlier S4.

On the S4s the transducer only feeds the oil pressure gauage on the dashboard, so if that is working there is nothing wrong with the transducer, but even if it isn't, its got nothing to do with the low pressure light problem you're reporting. The low pressure light on the dashboard is controlled by the separate low pressure switch through the relay I previously mentioned. If that switch was at fault I would expect you to see low pressure warnings all the time, not just at idle, so the relay would still definitely be my first port of call.

For reference the low pressure switch is A082N4039F if you end up needing it.

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Norfolk Mustard S4s #1 :)

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You could always screw a mechanical oil pressure gauge in & see what the idle pressure is.

Doesn't need to be in the dash, leave it in the engine bay & take a look after you've been for a run & she's up to temperature :thumbup:

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John W

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Always worth minding that low oil pressure at idle is not a vital indicator of the state of things in most cases. There is nothing going on which requires substantial pressure at idle. Still, one is wise to be vigilant on the state of things end-end in a Lotus. Critical targets for oil pressure have been framed by Tony Rudd, who knew the engine most thoroughly, and I recall these being a minimum value ( sorry, not recalled ) at idle then rising 10 PSI per 1000 RPM to a minimum of 45 peak. That describes the parameters around which the 900 Series were designed.


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