What resistor is need to drop volt?
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=83595
Printed Date: July 16, 2025 at 9:07 AM
Topic: What resistor is need to drop volt?
Posted By: 600rr
Subject: What resistor is need to drop volt?
Date Posted: October 02, 2006 at 12:57 AM
I am trying to hook up my remote start on my 04 honda 600rr and the accessory wire (on the bike) need to see 8.5 volt to activate the fuel pump but the alarm is putting out 12.2 so what resistor do I need to use to drop the voltage? or what do I need to do? thanks in advance Ryan
Replies:
Posted By: meh66
Date Posted: October 02, 2006 at 6:48 AM
You can use ohms law to figure out what resistance value you need, but you will have to find out how much current is going through the circuit. Ohm law is Voltage (V)= current(I) x resistance(R), so therefore (R) = V/I .You can find the current by meassuring it with a meter or maybe see how much current the accessory wire from the alarm is using. Example, if the current is 10 amps then you will need R = 8.5/10, therefore R = .85 ohms.
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MEH66
"Car Performance and Mobile Electronic Enthusiats"
Posted By: meh66
Date Posted: October 02, 2006 at 7:45 AM
Correction: I meant to say do you know how much current the fuel pump is drawing. I am thinking you can look at the pump itself or the fuse for the pump. I was curious as to how much voltage is the battery?
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MEH66
"Car Performance and Mobile Electronic Enthusiats"
Posted By: kaezoo
Date Posted: October 02, 2006 at 8:52 PM
If the ignition switch has a 12v input and only 8.5 volts of output, then it seems like the resistor must be built into the switch. It should be possible to disconnect the battery then use an ohm meter to measure the resistance through the switch between the input and output wires.
Posted By: 600rr
Date Posted: October 03, 2006 at 2:09 AM
I dont know why I didnt think about that but that sounds like the thing to do! I will have to do that in the next few days! thanks for the input guys! Ryan
Posted By: kgerry
Date Posted: October 03, 2006 at 3:32 PM
use an 8.5 volt + V Reg.... attach a heat sink for good measure and off you go....
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Kevin Gerry
Certified Electronics Technician
MECP First Class Installer
Owner/Installer
Classic Car Audio
since 1979
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