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Fitting low oil pressure warning light.


Hamish
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I have decided to fit a low oil pressure warning light to my TR3a. It’s a vanity project as it’s been fine for years without. 
 

you can take the pressure by replacing an oil gallery bolt and I’ve gone for 20psi. 
the switch and adapter have arrived just waiting on the led dash light. 
 

 

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Hamish,

Does a TR3A not have a oil pressure gauge?  Top left on dashboard?

Then all that is needed is to insert a T-piece into the connector where that comes off from the block, into which you can screw an oil pressure switch.   They are available inn various "NPT" thread sizes, and I expect you can get one to fit.   No need to break into the oil gallery elsewhere.

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2 hours ago, Hamish said:

As stated.the oil pressure gauge is via a banjo into quite a fine tube. The above seems to be a common practice for those going this route. 
this is a pic from the other forum of an existing set up.

would have preferred a single terminal self earthing switch though. Need to run twin core wire now. Or a short earth to where it screws into the block with an eye terminal.4E867DF8-ACE1-401E-96D9-5D62588A3D3D.jpeg.ca59e9ca3136b6292aa8027e7400049f.jpeg

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Always good to have. The standard switch on the Spitfire is on 3 psi or something like that. By the time it comes on the engine is likely to be toast, even if you see the tiny little light. Especially on the early cars where the instruments are in the middle of the dash.

I replaced mine with a 30 psi job and added a nice big light right in front of the steering wheel. Don't miss that...

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Fuel pump on the Scimitar (Rover V8) is powered view a relay off an oil pressure switch on the engine instead of an inertia kill switch. That's the old fashioned analog way for engine running. 

But as it's the same thing for your application kind of defeats the purpose. Without an ECU only other way I can think of is to use a vacuum switch on the inlet manifold.

Main problem there is you may not always have sufficient vacuum to ensure you keep the oil pressure warning light active. But if you could get a switch with a low enough vacuum setting. Might need to be quite big unless it's a piezoelectric one.

Worth a look maybe. 

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you could possibly use a signal from the charging light- wire a relay coil (might need to be high resistance) accross the charging light then the relay will switch depending on whether the car is charging ( engine running) or not. 

If the car has an alternator then the relay coil impedance might be an issue, but if you are using a dynamo then I suspect any old relay would be fine. If you have any electronics in the car (especialy if you are using intel inside) then a snubber diode would be a good idea!

 

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As I don’t do electrickery I think it’s a step to far for me. I’ll just stick with the light on until pressure reached. It’ll be an led so won’t drain battery or get hot if I need to have ignition on. ( I take coil feed wire off if it’s going to be for any time!)
 

I did think about the charge warning light as a pos feed. But it works the wrong way round as the light goes out when the engine runs. 
yes it has a little 40amp alternator.

H

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Do you think a “delay on” relay would work to be able to add a warning buzzer. so it gives the car time to start before being active in the event of low oil warning.  Or will the delay always be on. So useless as a warning buzzer ?
 

EASY TO USE TIMER SWITCH 0-150 SEC 12V/20A Delay ON CAR DAYLIGHTS DIRECT 12V OUT

https://www.ebay.co.uk/itm/280750912308

 

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21 hours ago, DeTRacted said:

It's not quite as easy as that on a '3a John.  The take-off for the pressure gauge is a banjo fitting on the oil filter head so the required adaptor would be quite complcated. 

Ah! So!    Thank you!

JOhn

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