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I'm not an engineer or auto mechanic, but I know what a diode is, and I know I need one for my application.

A little background (forgive me). I own a driving school, with a fleet of Toyota Corollas. Like many modern cars, these are equipped with a "lane change turn signal feature"... That is, if you move the signal switch only part-way, it will continue to blink 3 times after you release it. This confuses the heck out of our students, who attempt to cancel a signal but if they move it a little too far they see it still blinking, try to move it the other way, then the other way, etc. I dislike the feature myself as it's never proper to blink only 3 times. So, I'd like to disable the feature.

To figure things out, I bought a used turn signal switch matching this model and put it on my multi-meter. So I know which pins are connected as the switch arm is moved. As shown in my graphic, the car sees a connection to GROUND when the switch is moved either left or right, BEFORE it "clicks in". Then when it "clicks into position", it sees another connection... just one wire representing both sides. When the turn signal is turned off after this wire shows a closed circuit, it does NOT keep blinking.

So I'd like the switch to "lie" to the car, telling it that it's "fully clicked" whenever it's moved at all. I don't want to tear the switch apart or even remove it since it's inside the steering column, but the cable is easy to access. It seems I need to add two diodes, shown below in brown.

I've got room to put pretty much any diode between spliced wires, but the only diodes I've worked with are tiny ones on circuit boards.

Any suggestions for where I can find a diode and be reasonably confident it will work? I know almost nothing about diode specs. (Or is my theory completely flawed somehow?)

enter image description here

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    \$\begingroup\$ There's a good chance that this will work with the standard 1N4001, 1N4002 .... - 1N4007 type diodes. It does not matter which one of these you'd pick so get the cheapest. \$\endgroup\$ – Bimpelrekkie Jan 5 '17 at 7:24
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    \$\begingroup\$ It's hard to tell what specific diode would work the best, since we don't know what is the actually circuitry inside the car. \$\endgroup\$ – Bradman175 Jan 5 '17 at 7:26
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    \$\begingroup\$ What happens if you just tie "fully clicked" to 13V? \$\endgroup\$ – RoyC Jan 5 '17 at 9:08
  • \$\begingroup\$ As FM says, 1N400x series will almost certainly work if any do. These are 1A continuous rated which will be below relay current needs. Lamp current MAY be higher but you are very unlikely to be switching these directly. Worst case you could power a relay to provide the fake-connection when the switch is partially closed - but shouldn't be necessary. You also could implement a small and simple cct with a MOSFET and maybe a very few other parts BUT a diode is liable to work. ... \$\endgroup\$ – Russell McMahon Jan 5 '17 at 11:09
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    \$\begingroup\$ You may want to check if that feature can be disabled via software configuration ("coding"). \$\endgroup\$ – JimmyB Jan 5 '17 at 13:16
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FakeMoustache actually should get credit for answering my question, but he posted it as a comment and an answer should be posted here.

[Edit 12/5/2018: I have now done this successfully with three Corollas. Works great!]

Just in case someone has a 2014, 2015, 2016, or 2017 Corolla, below is what I provided to the mechanic to make this simple modification. Even as an experienced driver, I don't like the lane change feature. As FakeMoustache stated, use any of diodes 1N4001, 1N4002 through 1N4007. I used 1N4007's, but probably should have used 1N4001's since the leads are thinner and easier to work with.

Notice the black wire doesn't necessarily have to be cut, but I find it easier than stripping and splicing mid-wire.

Also notice there are two pink wires. Don't splice into the wrong one! See the illustration.

enter image description here

My work is a bit sloppy but it works.  For this car I would have been better off with IN4401's which have smaller leads. Make sure you insulate.

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Since the connections are very likely inputs to a MCU, they should carry minimal current. I would estimate in the order of ma, so any 1 amp, 24v diode (or better) should work - electrically. However, adding the diodes as shown, you will be reducing the time delay between the "direction" and "latch" signals, so the MCU might get "confused." So, it should work, but it is not guarantied that it will always work.

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  • \$\begingroup\$ As noted in comments below the post, I did it and it worked great. FakeMoustache provided a perfect answer, naming specific diodes which I already had on hand. \$\endgroup\$ – PaulOTron2000 Jan 7 '17 at 16:09

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