diodes

I have a 94 Dodge Intrepid & a Omega K9 Mundial-4 alarm. I'm confused about what diode do i use for the negative door triggers. 4001, 4002, 4004 or 4007? What's a good way to install them correctly also. Thank you.-dk-

The higher the number, the higher the working voltage. The 4001 is rated at 50 volts. Any of the numbers you posted will work exactly the same in an automotive application.

Though the 4 & 7 are probably the most common and can also be used for relay coil spike suppression (the 1 & 2 are too low).

The backlash spike is such a brief time, we keep 4001 and that is all we use. I have never seen or heard of one shorting when strapped across a relay coil.

It's PIV punchthru since the spikes are typically 100V-200V. Unlike over-current spikes, high over-voltage can mean almost immediate rupture (viz ye olde static damage). Not that I've ever had it, but I've never used lower than 200V (IN4003). But so many sources have stated similar - ie, 1N4004 for 12V coils.

No comment I've just bought 500 x 4004, looks like an ammo belt for a small machine gun!

The ONLY way to buy! I still have heaps of signal diodes (IN914/IN4148) I bought cheap decades ago (maybe 2c each, but you can buy them on Oz eBay for $42 mounted in a fuse body to increase alternator output by ~0.6V LOL!). And relatively recently I bought a 100-pack of 1N4004s (or 4007?) and I think a pack of 1N540x 3A equivalents. Not that I use many - maybe 5-10 per year if that - but IMO the packs rival the cost of future 20-minute trips (else postage) for the next odd requirement. Now, I wonder where I put them? Ammo belt eh? Let's see, a voltage drop of 0.6V... their mass of ? times v-squared /2....