Oil pressure sender

[Trevethan]

I am fitting a new instrument panel, which comes comeplete with senders.

I am having problems getting the old oil pressure sender off. I am a bit loathe to use a girt big wrench on it and so far my efforts with a smaller one have failed to budge it.

I have tried connecting the old sender to the new display -- there are two wires fromt eh panel for oil, one for the warning light and one for teh guage.
The new sender has just 1 terminal on it I assume it earths through the engine.

The old one has 2. I have tried connecting one of the old sender terminals to the guage and another to the earthing stud -- no joy (i.e oil lamp fails to light)

I have squirted some WD 40 at the old sender and I hope it will ease, but any other suggestions for getting the old one off without buggering up the engine or for wiring it much appreciated..

Engine is an old Lister HRW4

Thanks

Nick



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[Plum]

1) I assume you are only refering to a warning light and that your reference to a "gauge" is a typo. You are right in assuming most oil pressure senders use the engine as the earth return. Assuming your old sender is for a warning light and neither of the two terminals is also acting as an earth, then you need to connect the wire from the warning light to one of the terminals and connect the other terminal to earth. With the engine not running, try checking continuity between the two terminals and between the two terminals in turn and earth. Are you sure your engine is earthed while doing these tests?

2) if the above works, then you do not need to remove the old sender. these senders are almost always on a tapered thread and usually fitted with a sealer and if you sheer it off you have a big problem, particularly if you have poor accessibility. WD40 on a tapered and sealed thread is unlikely to achieve anything.

3) some old engines have a second tapped port into the oil gallery to take a gauge. Is there a blanking plug close by that you can put the new sender into without removing the old one?

Hope these thoughts help.

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[Trevethan]

I have both a warning light and a gauge!

The senders are both a drum like affairs about an inch in diameter. the old one One has 2 terminals, the other just the one

The engine is earthed.

I have played with the lamp cable and tought it to the engine turns it on. toughing to either of the terminals on the send and its off. Tried earthing second terminal and still no light, so assuming no conuity.

The boat did have a caipllary type guage stuffed away under the console, but when I traced it back it didn't go anywhere....

I'll see if I can find someone at Lister than can say whether there are two take off points.. the manual is useless....

Thanks for the advice.. might have a fiddle later and try your suggestions


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[Plum]

Assuming your warning light worked with the old instrument panel and old warning light sender it is an unlikely coincidence that the sender has gone wrong at this time. Does the old sender turn the new light "on" when there is oil pressure? In other words, are the contacts open at rest and closed at pressure? Although I have not come across this before, it would make for a more fail-safe pressure warning as with the conventional system if the wire drops off the sender you get no warning, but with a normally-open sender, working through a normally-closed relay, if there is a problem with the wiring in the engine compartment the light would come on as well as if the pressure dropped.

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[Trevethan]

I suspect that I have another set of oil senders tucked away on the back of the engine where its hard to get to.

Lister Petter said there were a series of plugs avaliable, and I suspect the oil light switch is there, plus I might another working sender....

Thanks for all your help!



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[andyball]

Is it possible that your old "sender" is a a pressure sender, not a switch?....what lights & guages did you have working before you fitted the new panel?.

If you've a cheapy multimeter , put that across the terminals of the old one & measure the resistance, if it's not totally open circuit then it's likely meant to be connected to the guage, not the lamp.

There are at least 3 "standards" of sender resistance.....vdo/most uk stuff.....usa made faria (& others) + vetus (veglia) are all different, as far as I can tell.

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[Born_Free]

If you really need to get the old sender out and you can run the engine then do so and try the spanner again, the heat from within could well be enough to enable you to crack the seal and get it out, if you can't run it then try applying heat gently to achieve the same result. Careful application with a small gas torch (ie . the soldering type) Spread the heat over the area generally to avoid damaging the engine should do it, and have a fire extinguisher close to hand. Best of luck!

<hr width=100% size=1>I have nothing to declare, except my genius
(Sorry Oscar)