do all relays need to be diode isolated?

OK Kevin, point taken, I still prefer to use them because the cost and time factor makes ME feel better, incidentally why do they (DEI) ask you to use diodes on the 5902 diagrams.

Like I said before - they won't hurt! What diagram are you talking about - I looked through the 5902 install manual and didn't see a single diagram showing a diode added across the coil?Kevin Pierson

You might be right, it was the 5901 lock/unlike wires but that used a flip flop output so that was probably the reason. Its 9:30pm here, I'm watching TV so I can't be bothered to track down the reference, there are about 5 revisions to 5901/2 installation diagrams

Hey old spark, What could I do to test or check and see if I need a reverse biased, isolating or suppression diode? And would it be to much to ask you to explain how to wire these up if I do decide to add them for a little extra protection for my wiring. Thanks again

If you are connecting a relay to a 200 milliamp output of an alarm, it already has a diode.  if the output is only capable of 200 milliamps, they know you are connecting a relay to it.

The diodes you mentioned are all the same.

i am an idiot wrote: If you are connecting a relay to a 200 milliamp output of an alarm, it already has a diode.  if the output is only capable of 200 milliamps, they know you are connecting a relay to it.

how about the relay I will be using for my sirens? I'm going to be using the (+)siren output from my alarm to power the coil

The siren output of an alarm is driven by a transistor.  It will be fine with or without the diode. 

Thanks I am an idiot. I want to run the relay for the sirens just to be sure i don't over draw current from the alarms siren output. t&t tech - do you say this because of the low aH battery that comes with the 520t is to small to drive the sirens or is it because the 520t diode box cannot handle the current needed? BTW I am using a relay to reverse the polarity of my headlights so the backup battery will not be activating the parking lights. and my additional siren only requires 150mah.