Its supposed to prevent a surge of up to 200 volts from going to the alarm brain. I read this on a link to a website someone posted here and was wondering if anybody does this or thinks its really nessecary?

 

It depends on what I'm using the relay for. Usually if the relay is tied into a circuit that can be damaged due to surges (parking lights, starter, ignition, fuel pump, etc), I'll use a diode. If the relay is used for amp turn-on, trunk release and other similar functions, I won't use one.

Diodes also help extend the life of a relay which is another good reason to use it on critical security functions.

Another note....you have to make sure that the diode is installed correctly. There is no set rule for contacts 86 and 85 on a relay concerning which is 12v+ or ground. What matters is that they are opposite in polarity. So if you use 12v+ on 86, the cathode side (band side) has to be connected to 86. The same holds true if you use 12v+ on 85 instead.

 

ok, that makes sense. I actually would be using it for a door lock, another for starter kill and another for fuel pump kill. I suppose I'll just use one on all of them. Might as well spend the time to wire in a diode now than rip everything apart later to put one in. Which diode would I use for this. Which color bands would be on this paticular diode?
One more question, my alarm has a wire that will put out a constant ground(-) when armed and thats going to connect to 85 and 86 to an iginiton source that reads +12volts when in the "on" or "start" position. This orange wire, can it be used on 2 different relays. Like connect it to the starter kill and than run another wire from it to a fuel pump kill?

 

Here's the diode you will need (your local Radio Shack should have them):

http://www.radioshack.com/prod...-1103

The band side (cathode) is usually silver. In your setup, connect this side to 86 and connect the other side of the diode to 85.

You can use the orange wire (ground-when-armed) to trigger multiple relays and/or a window roll-up module. When used with relays, I like to isolate the trigger with a diode (separate from the one used on the relay itself). Just connect the band side to the orange wire from the alarm and the other side goes toward your relay.

BTW...what alarm do you have?

 

I have a crime stopper cs--2013fm. its one of those paging units.

 

be sure that the component you are using is a diode and not a resistor. diodes are usually black with a silver band on one end. if it has a couple or more colors it is probably a resistor, and will yield much different results - won't provide the protection that you are looking for.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HondaDriver4Life &raquo;</TD></TR><TR><TD CLASS="quote">It depends on what I'm using the relay for. Usually if the relay is tied into a circuit that can be damaged due to surges (parking lights, starter, ignition, fuel pump, etc), I'll use a diode. If the relay is used for amp turn-on, trunk release and other similar functions, I won't use one.

Diodes also help extend the life of a relay which is another good reason to use it on critical security functions.

Another note....you have to make sure that the diode is installed correctly. There is no set rule for contacts 86 and 85 on a relay concerning which is 12v+ or ground. What matters is that they are opposite in polarity. So if you use 12v+ on 86, the cathode side (band side) has to be connected to 86. The same holds true if you use 12v+ on 85 instead.</TD></TR></TABLE>

I would use one on most car devices. Am amp remote uses a small transistor to turn the amps on. If it sees repetitive high voltage spikes you take the chance of eventually breaking the part down. A lot of relays come with these prewired inside the relay. So it would be wise to actually look at the schematic of the relay you are buying.