Toyota 5FBC25:
back up alarms.

This is a new one. I am trying to replace a back up alarm on this toyotaSo I hook it up 48vdc Put it in reverse works great (beep beep beep) then I use the hydraulics( SCR-Transistor I'm not sure) and it cuts out so I check for voltage drop and it drops a volt or 2. No big deal. I put it in rev and drive a bit and it cuts out.It cut out when the SCR is working. OK So I hook it up directly to the battery(beep, beep, beep) Touch the accel pedal or the hyd and it stops. I check voltage at alarm and there is 48 volts there but is dosn't work while in SCR range WTF And yes I removed the battery from the truck to remove stray battery volts from frame, Which there was alot. Isolated it with rubber and installed.
  • Posted 22 Jan 2010 00:15
  • Discussion started by Davie
  • Ontario, Canada
Showing items 1 - 5 of 5 results.
I've seen this problem and it seems some alarms do pick up interference. I would try a different brand.
  • Posted 26 Jan 2010 09:41
  • Reply by mrfixit
  • New York, United States
On this back up alarm there is no ground tab. When I hook this back up alarm up directly to the battery posts it cuts out when I use a hydraulic function or drive. I belive it may have something to do with interference from the transistors or SCR's
Any Ideas???would be appreciated.
  • Posted 26 Jan 2010 04:08
  • Reply by Davie
  • Ontario, Canada
on this bac-alarm, is there a metal tab attached to the negative connection screw/stud that also is bent around to allow the mounting hardware to go through a whole in the tab? on electric forklifts this tab must be removed.
are you saying that even with the alarm wired direct to the battery positive and battery negative heavy power cables, it does not beep continuously and is effected by the operation of the truck??
there may be some instructions around somewhere that show how to install a small diode and capacitor to act as a noise filter on the alarm's circuit to cut down the electrical noise that interferes with the alarms operation
  • Posted 22 Jan 2010 21:56
  • Modified 22 Jan 2010 21:59 by poster
  • Reply by edward_t
  • South Carolina, United States
"it's not rocket surgery"
OK I eventually hooked the Back up alarm directly to the battery to test. I also hooked my meter to it as well So the back up alarm worked constantly until I either accelerated or used the hydraulics. I believe there is some kind of interference in this system. While hooked up this way I drove until 1A kicked in then it started working until I let it go back into scr range. So it only acts up when using the SCR Or transistor(not sure which one this is. I have tried putting a diode in the positive wire. I was going to try a different manufacturer for the Back up alarm. This Back up alarm SHOULD work. It should work from 24-48vdc
  • Posted 22 Jan 2010 09:14
  • Reply by Davie
  • Ontario, Canada
when you say "hook it up 48vdc"; can you tell us where did you get battery negative, where did you get Battery positive.
  • Posted 22 Jan 2010 04:37
  • Reply by edward_t
  • South Carolina, United States
"it's not rocket surgery"

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The now-ubiquitous 'Keep Calm and Carry On' phrase was coined by the British government in 1939 to encourage its citizens to stay strong. Posters with the slogan were printed but never officially issued and only unearthed in 2000.
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Fact of the week
The now-ubiquitous 'Keep Calm and Carry On' phrase was coined by the British government in 1939 to encourage its citizens to stay strong. Posters with the slogan were printed but never officially issued and only unearthed in 2000.