Oil Pressure Switch - Oddity.

[geoberni]

Having had a successful run out yesterday to the Great British Car Journey, where Basil won me a 1 year membership (for the 2nd year running)....
I started him today, prior to some maintenance activity, and noticed the Oil Lamp flickering at idle...
Did a resistance check on the switch and it's not operating cleanly as a switch, in the space of a few seconds, it's wandering all over the place from 2 Ohms to a few KOhms and back, registering many other resistance figures in between...

Only when I came to remove it, did I realise it's not the one I was expecting...
Stupidly small nut hidden behind a large round switch body.
Obviously been in there years and just no way can I get a decent spanner onto it, unless I strip everything from that side of the engine.

Oil Switch.JPG (65.08 KiB) Viewed 3445 times

So just out of curiosity, does anyone recognise it as being from a particular car model??
I think I'm going to have to wreck this to get it off.

[svenedin]

I recognise that as similar to the type I last removed from my car. I remember it was a bit of a fiddle to get off but I didn't strip anything off the engine. Fortunately it was not very tight. I assumed the switch I removed was the original from when my car was made. Incidentally, I also recall it had a parallel thread and a copper washer unlike the modern tapered thread switches.

I will have a look for a photo.......

Stephen

[svenedin]

IMG_9884.jpeg (1.47 MiB) Viewed 3438 times

IMG_9886.jpeg (1.58 MiB) Viewed 3438 times

[svenedin]

The is the new one, not the awkward old one but can you not approach undoing the old switch from the bell housing direction?

Stephen

IMG_9887.jpeg (2.51 MiB) Viewed 3436 times

[philthehill]

Those old oil pressure switches are quite tough enough to allow a pair of grips to hold the body and undo. The switch is not done up very tight so should come undone with out too much effort.

[geoberni]

Thanks guys, particularly Phill for saying ....

Those old oil pressure switches are quite tough enough to allow a pair of grips to hold the body and undo......

I got a pipe wrench to the casing today and it did budge without tearing the casing off, which I had feared it might.
To paraphrase HG Wells and 'War of the Worlds' slowly but surely, it came undone .
Once about 1 revolution completed, a 7/16AF would turn it without slipping, which it had done last night.
It's been on a long time, having has a slap of silver paint at some time...
.

20250507_103933.jpg (369.54 KiB) Viewed 3352 times

.
Turns out it's an AC Delco, and there's currently a pair of NOS ones on ebay for £30, apparently being OE on Hillman/Commer cars.

Once off, I was able to connect the meter to it again and just lightly tapping it on the bench made the resistance of the contacts vary, so obviously loose inside.

[philthehill]

Well done