Yamae

I don't know much about it but I think it's a reed switch. You can find some about it at here.
http://www.meder.com/index.php?id=2724

Hope this helps.

fsuguy

Yamae,

thanks for the link. I checked it out and was not able to find out too much. There appear to be several different sensor types, and the only thing I can come up with is that there is some sort of density/proximity/magnetic sensor inside the barrel guides in the LS 400 oil level sensor. I tested the float for magnetism, but did not get any reaction. I am attaching some pictures I took in the hopes that someone here will know exactly how these darn things work.

It looks like all the magic is inside the float guide and the float pivot, since the float itself is completely insulated from the electrical connections; the connector and wiring are simple enough, and the wiring appears to be a closed circuit as shown by the top of the float area. Somehow, the rising and falling of the float changes the voltage across the two leads from the barrels!??? I am sorely tempted to unsolder (?) one of these to see what exactly is inside, but would rather wait and see if anyone here has any insight!

aptoslexus

The float is connected to a variable resistor. Probably works much like this: http://auto.howstuffworks.com/fuel-gauge1.htm

sha4000

iTrader: (1)

That was a very informative article, thanks.

fsuguy

OK chaps,

I think I've found out how this oil level sender works, thanks to the link from Yamae, and a little experimentation. The float has a collar or bushing which is highly magnetised at the top (picture added showing the thin collar). I missed this magnetic effect since it is very localized and acts on the hidden reed switch inside the float guide (the brass/copper barrel), I missed this because I expected the magnet to be embedded inside the float at the end where the float runs up and down another bigger copper/barrel which also looks like it may have a switch inside it. As the oil level fluctuates, the rising and falling float, and therefore the magnetic field affects a spring inside the reed switch which either forces the contacts together or apart to either close or open the circuit, and thence illuminate the idiot light! Pretty neat, but is the whole thing justified for $400+???

I suspect that the heating/cooling cycle of the oil causes the solder to allow oil leakage into the reed switch space and cause it to malfunction intermittently. Will know for certain when I finally desloder the one I have out and take a looksee!!! Also, I think that the shape of the float (the two crescents at the ends, but note the lack of any magnetic collar!) is probably due to a one-size-fits-all approach, where the magnets can be added for models that have that option/specification.

Yamae

Now you understood. You also need to know that there exists a temperature limit called "the Curie temperature" which is explained here below.

http://en.wikipedia.org/wiki/Curie_temperature

A magnets becomes not a magnet any more when it is heated up to the Curie temperature. Most of magnets become so at around 130 degrees C which is the high side of oil temperature. It simply means that you need a special magnet and a reed switch. Also an engine which experienced too much overheat tends to show this problem.

fsuguy

Yamae,

Thank you! I sort of vaguely remembered from my physics experiments back in my school years that heat destroyed a magnets properties, but never knew the effect had a name!! It's good to learn something new everyday, though!

Now all I need is a new float and reed switch to rebuild my Oil Level sender, unless the components cost $400! By the way, I salvaged a couple of these senders from the junkyard and one of them is toast, the other seems to be ok, but it is from a '94 and the total length from mounting base to the bottom of the float is different; also, the connector plug is different, although looking at it from the top (engine bay) you wouldn't think so! If anyone wants to see a side by side comparison of pre-'94 and '94, let me know and I will post a couple of pics.

Yamae

You are welcome fsuguy.Thanks for showing me the actual oil level sensor. It's a good experience for me to see your photos.

Automobiles use many different techniques and materials. I only knew electronics related affairs, but I'm getting to know different affairs these days trying to maintain my old 98 Celsior.

fsuguy

You are most welcome, Yamae. I found some information on the following site about reed switches, but I think an EE like you would probably understand it better, since most of the info is compiled by engineers: http://reed-switch-info.com/

Here is a pic of the sender from a '94 and one from a '91 LS400. The difference is slight, but clearly visible - the one with the grey connector socket is from the '94 LS400.

Also, I think you should know that although removing the bolts (10mm) is easy once you get to them, actually taking the sender out is not very straightforward because of the double bends in the arm - you have to gently (I think the float can break easily!) go through several twists and turns while gently pulling it up and out!

treflip

I too am trying to rebuild the oil level sensor. I have been successfully able to remove the read switch on a different unit (different level design, same components) but ended up breaking the magnetic switch from the other container. I thought I was going to find a bimetal temperature switch of sorts that breaks continuity when heated up!

I may end up replacing it with one if I can't find the magnetic switch from digikey. Were you able to source these components or no? I am about to go looking...

-Tre

edit: OK I was able to figure out the component inside the magnet. I had pulled the leg off mine and didn't see that the glass tube was still inside, making the component look like a solid piece! Fortunately I had another switch I purchased off ebay and when testing it the bulb pulled out completely... it was another reed switch!

So after looking around on the internet I have purchased a couple off sizes (need 1.8 x 2 mm for the one with a magnet and 2.2 x 12mm for the float activated switch.) I also created a pdf with a bit of information on the switch and components.

I consider this some payback for the help I got with my radio install and vvt code (and a couple other things!)

Hope it helps someone out there!

casmas54

I just purchased a 1990 ES 400 with less than 80,000 miles. The previous owner had tried to start it after letting it for several months. It blew the 100 amp fuse to the alternator. When I looked at it, it would start and drive but there were no other electrical functions, lights, etc.. I replaced the fuse and most things were working except for radio, brake lights and a few other minor things. The battery light and one other light were still on.I brought it home.but now what really worries me is that the oil light is on all the time although the oil is all the way up on the dipstick and fresh. Also the low coolant light is on constantly now too. I am going to replace the oil sender and filter tomorrow. The way the engine is running I suspect there is no issue with the oil pressure. I am guessing it is an electrical issue due to the blown fuse or possibly an ongoing issue with the alternator. Any enlightenment would be greatly appreciated..

Yamae

The 100A ALT fuse often opens when the battery is reversed or the jump cable is reversed. If so, other than the open 100A fuse, there usually are some more damages but I don't know much about a ES400.

treflip