safe to run two relays off of an alarm?

Printed From: the12volt.com
Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=100514
Printed Date: May 15, 2025 at 1:52 AM

Topic: safe to run two relays off of an alarm?

Posted By: Sad, little man
Subject: safe to run two relays off of an alarm?
Date Posted: December 28, 2007 at 1:34 PM

Hi, I'm wiring something up in my car that will require the AUX outputs of my alarm to drive two Bosch style relays at the same time. I have to coils wired in parallel. From what I've read, Bosch relays draw around 150mA to run the coil. The alarm's AUX outputs are labeled at 250mA on the wiring label on the alarm module itself (It's a Compustar, BTW.) Would it be pushing it to run two relays off of one output, or should I be ok? Basically, are the ratings on the alarm conservative, or should I not even consider exceeding them at all?

Edit: Just tested with my meter... Both relays together pull around 260mA, and for some reason the reading drops steadily as the relays continue to be energized. Hmmm, 10mA over. I should be able to get away with that, right?...... Right? posted_image

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'96 Mazda Miata

Replies:

Posted By: anaxagoras
Date Posted: December 28, 2007 at 1:39 PM

I don't know about how the ratings are on the compustar.

But couldn't you just use an extra relay and branch the 2 off of one? Have the compustar activate relay A, then have relay A activate B and C?

Posted By: Sad, little man
Date Posted: December 28, 2007 at 1:44 PM

Yes, I could. But, to be honest, this is in a Mazda Miata, so space was already tight when the car was stock, and since then, I've added an obscene amount of electrical acessories. Everything is wired up well, and has been reliable, but the car is turning into a bit of a wiring nightmare. It would just be nice to keep things simple. Right now I'm doing the wiring in order to remote activate my seat heaters. It already required two relays per seat so I'd like it if I didn't have to find a place to stuff any more. As I said, at 10mA over, I doubt anything terrible is going to happen. I'll probably go ahead with it unless someone comes up with a really good reason why I shouldn't.

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'96 Mazda Miata

Posted By: tedmond
Date Posted: December 29, 2007 at 12:32 AM

you should be fine. i remember i used ground when running from a compustar to run 3 differant relays. bypass mod, defrost, heated seats and no problems so far ahah. well its not my car so untill then, no worries