Do I need to use Flyback with my relays

[Noddle]

Hi,

 

I'm in the process of re-wiring my MS II system, including my fuse / relay box, and I'm wondering if I should uses 1N4004 diodes to enable flyback on the relays I'm using, or am I'm been to paranoid about it.

 

Nigel

[goodoldjam]

I think you shouldn't have to worry about it, V3 boards had built in flyback circuits. Learned a bit from talking with Jacob about his fan circuit. Basically only time you need to add one is when you add a new transistor circuit. If you did need to add some, your transistor would have already failed.

This is a very cool read. http://www.autoshop101.com/forms/hweb2.pdf

[Matt Cramer]

The V3.0 flyback circuit is for the injectors. Using the diode is a good idea.

[goodoldjam]

The V3.0 flyback circuit is for the injectors. Using the diode is a good idea.

Now I'm thinking I need to do it. So The Fuel pump relay is going to need a diode then. So does the relay board have diodes in place?

 

Edit: Answered my own question nevermind. I see on a one of your DIY writeups that you added a diode for IAC.

Edited July 29, 2010 by goodoldjam

[Matt Cramer]

The relay *board* does not have a flyback diode in place, but there is a flyback diode for the fuel pump relay on the main board. It's a somewhat different type as it uses a zener diode to pull a voltage spike to ground rather than running the voltage spike to the 12 volt plane.