Which zener diode

Got an electrical gremlin? Ask the question here.
Post Reply
User avatar
Anton
I spend far too much time on here
I spend far too much time on here
Posts: 3693
Joined: Tue Jan 12, 2010 12:12 pm
Location: London

Which zener diode

Post by Anton » Thu Mar 22, 2018 9:49 pm

Hey, ppls. A friend of mine wants to put a pair of relays into his Toyota to switch his high power headlights. Recently the current draw (2x 60w bulbs, so 10a total load) melted the switch inside the indicator stalk, after which no headlights (although thankfully no fire).

I'm thinking a zenier diode would be good, to stop high currents flowing back through the circuit and maybe even into his ECU, but what voltage? Would 15v be ok, or should I go for 17v? I remember reading somewhere that +3v is a good rule of thumb, meaning that a 17 would be more appropriate, but my memory might be shonky. Or shcottky... :brows:
1985 SJ413VX (SJ50V) with SPOA, rear disc brakes, 31x10.5R15 Kaiman Malatesta tyres, an MOT and a lot left to do!

My: Build thread To-do list Pay and Play map

User avatar
Robert.m
Got muddy boots
Got muddy boots
Posts: 22
Joined: Sun Jun 11, 2017 4:42 pm

Re: Which zener diode

Post by Robert.m » Sun Mar 25, 2018 9:02 pm

I thought wiring the HP lights through a relay would be sufficient to avoid melting anything.

User avatar
Anton
I spend far too much time on here
I spend far too much time on here
Posts: 3693
Joined: Tue Jan 12, 2010 12:12 pm
Location: London

Re: Which zener diode

Post by Anton » Mon Mar 26, 2018 12:29 am

It is. I'm not worried about the lights melting anything once the relays are in, I'm worried about the voltage spikes that relays cause when their electromagnetic field collapses.
1985 SJ413VX (SJ50V) with SPOA, rear disc brakes, 31x10.5R15 Kaiman Malatesta tyres, an MOT and a lot left to do!

My: Build thread To-do list Pay and Play map

Post Reply