Use 0-5v+ to Switch 12v Relay
Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=28579
Printed Date: July 13, 2025 at 11:16 PM
Topic: Use 0-5v+ to Switch 12v Relay
Posted By: wildside
Subject: Use 0-5v+ to Switch 12v Relay
Date Posted: March 17, 2004 at 8:47 PM
I have a 99 ford f150 truck. The actuators fot the locks SUCK! I am replacing them with better ones. However the switch does not show a full 12V when switched and is not enough to energize a 12v relay. Does anyone know how to create a way to latch a 12v relay with less than 5v?
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It's not how fast you drive, it's how you drive fast.
Replies:
Posted By: its_radio_shop
Date Posted: March 17, 2004 at 9:50 PM
You can switch a relay with 5v yes. I would however look at the switching issue. If the switch will not activate a relay then its not going to activate your actuators that "suck". You have a problem with your switch if it wont activate a relay. Your switch should not be giving you 5v output.
Posted By: auex
Date Posted: March 17, 2004 at 10:44 PM
Are you testing the wiring coming off of the switch or the wires at the actuators?
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Posted By: wildside
Date Posted: March 17, 2004 at 11:24 PM
Ok. Sorry. I must have not explained it well. Heres what is happening. The truck has 2 wire actuators that use the reverse voltage method. The switch in the truck does all the work of reversing voltage. However... the truck has a theft module that uses relays and what is happening is I think that module is going out. What I want to do is not only replace the stock actuators with stronger ones, but I am going to feed them a direct 12v+ lead fused without going through the module. With the module inline I can still use the keyless remote and both doorlocks. When you hit the lock the first time it sends around 11v. the more you hit the lock, the voltage starts to drop down to around 3v by the about the 5th click. Apearantly this is a common problem with this truck. I woant to use the signal being genereated by the module when you click the lock to activate a relay to send a fresh 12v signal to the new actuators. I could just use the stock ones and jimmy it up this way to fix the problem but why not make it better?
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It's not how fast you drive, it's how you drive fast.
Posted By: its_radio_shop
Date Posted: March 18, 2004 at 12:04 AM
Try hooking up a pair of relays to the output of your module and eliminate the load of the actuators. See if the voltage drops when the module is running only the relays. The small load of the relays may make the voltage drop much less adverse than when its running the actuators. If thats the case, use the diagram in the door lock section of this site for reverse polarity actuators and wire your relays and actuators as it shows except instead of connecting the relays to an "alarm output" you will be connecting to your lock module. If your module is positive output you will need to change the fused +12V portion of that diagram to ground, and your 87A terminals to +12V. See what you come up with.  btw, those relays should switch fine quite a ways below 12V at a slight increase in amperage of course but at around 1/4 amp, an increase still wont be near the load of the actuators.
Posted By: wildside
Date Posted: March 18, 2004 at 1:51 PM
Thanks, I'll try that. I think my problem is that I am expecting the output form the module to reverse the voltage, BUT... what i think is happening, (and i'll have to check it with a meter) is that the switch and module are actually sending a negitve pulse which is closing the stock relay. I looked in the book and this would make since. I'll try what you said and let you know. Thanks.
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It's not how fast you drive, it's how you drive fast.
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