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General Category => Modifications => Topic started by: ccsct203 on September 14, 2009, 07:32:28 PM

Title: Low Coil voltage? Ideas
Post by: ccsct203 on September 14, 2009, 07:32:28 PM
I'm looking at my FJ repair manual here and wondering if the +12v side of the coils and really seeing +12v
After reading about the headlight problem and the posibility of a 2 volt drop by the time voltage reaches the bulb, could the coils suffer the same low voltage issue which in turn would reduce the output of the coils.
the book says the +12v red/white wire comes through the stop switch directly.
If I find the voltage lower then the battery voltage would it make sence to install a relay and wire the + side of the coils and only use the stop switch to operate the relay?
Ideas?
I'll check the voltage this week
Title: Re: Low Coil voltage? Ideas
Post by: the fan on September 14, 2009, 07:51:08 PM
I really doubt you are seeing a full 12v at the coils.

Here is some light reading...
http://www.oldskoolyzf.com/forum/viewtopic.php?f=7&t=458 (http://www.oldskoolyzf.com/forum/viewtopic.php?f=7&t=458)

http://www.oldskoolyzf.com/forum/viewtopic.php?f=6&t=562&hilit=relay (http://www.oldskoolyzf.com/forum/viewtopic.php?f=6&t=562&hilit=relay)

http://www.oldskoolyzf.com/forum/viewtopic.php?f=6&t=716&hilit=relay (http://www.oldskoolyzf.com/forum/viewtopic.php?f=6&t=716&hilit=relay)
Title: Re: Low Coil voltage? Ideas
Post by: ccsct203 on September 14, 2009, 08:02:07 PM
Bingo
"That's what I'm talking 'bout"
Title: Re: Low Coil voltage? Ideas
Post by: the fan on September 14, 2009, 08:13:20 PM
I knowz, cuz ahm smaaaht.
Title: Re: Low Coil voltage? Ideas
Post by: SlowOldGuy on September 14, 2009, 10:24:48 PM
Jon Cain is a big proponent of running the coils off of a relay.  When you say "stop switch" do you mean the ignition switch?  Typically there is a voltage loss through the ignition switch.

Basically, it couldn't hurt to hook up a relay to drive the coils.  Much cheaper than new coils.

DavidR.
Title: Re: Low Coil voltage? Ideas
Post by: threejagsteve on September 15, 2009, 01:25:45 AM
Quote from: the fan on September 14, 2009, 07:51:08 PM
I really doubt you are seeing a full 12v at the coils.

Here is some light reading...
http://www.oldskoolyzf.com/forum/viewtopic.php?f=7&t=458 (http://www.oldskoolyzf.com/forum/viewtopic.php?f=7&t=458)

http://www.oldskoolyzf.com/forum/viewtopic.php?f=6&t=562&hilit=relay (http://www.oldskoolyzf.com/forum/viewtopic.php?f=6&t=562&hilit=relay)

http://www.oldskoolyzf.com/forum/viewtopic.php?f=6&t=716&hilit=relay (http://www.oldskoolyzf.com/forum/viewtopic.php?f=6&t=716&hilit=relay)

Great link, the fan!

I've copied the instrux text into an .rtf, and saved the diagram. Seems to me this how-to oughtta go in the Files section as a more-permanent reference.
Title: Re: Low Coil voltage? Ideas
Post by: ccsct203 on September 15, 2009, 06:46:40 AM
Talk'n about the ignition switch and the switch on the right handle above the starter switch.
I measured my voltage with the key on and found 10.8 volts. :dash2:
Why did it take me this long to think of this easy fix???
Title: Re: Low Coil voltage? Ideas
Post by: the fan on September 15, 2009, 09:14:16 AM
I could easily write something up and add it into the files. I would like to get my hands on an FJ first and make all the measurements and take a few pics. I imagine it has never happened here in part due to the existence of aftermarket ignition set-ups. These are not available over in the YZF world.
Title: Re: Low Coil voltage? Ideas
Post by: threejagsteve on September 15, 2009, 10:13:34 AM
I have the suspicion that there'd be a few others who'd be interested in improving their ignition without having to spend big bucks for one of the aftermarket setups.

I'm planning to do the mod myself... I could certainly take the pics and measurements and do any additional writeup needed. I don't have the full Acrobat, though, so somebody will need to make it into a nice, neat pdf.

But my new brakes should be here tomorrow and I've got to get that sorted first and my rebuilt front end dialed in, so it'll likely be a couple of weeks, maybe a month, before I'm ready for the next round of upgrades (though I'm already making plans... :P).

Title: Re: Low Coil voltage? Ideas
Post by: ccsct203 on September 19, 2009, 08:20:59 PM
I made my relay and harness tonight.
Used a 30 amp 12v relay and 12 gauge wire
soldered all the connections even the ones going to the relay and then heat shrinked tubing
mounting it to the left side of the battery box
that should fix my 2 volt loss
I'll report back :morning1:
Title: Re: Low Coil voltage? Ideas
Post by: MyFirstNameIsPaul on September 20, 2009, 09:16:35 AM
When I installed my Dynatek ignition system I checked the resistance of the kill switch. It was 15 ohms.  I've installed an accessory bus, so I ran a line from that, which was .5 ohm.  I can't say if it made a difference because I did too many things at one time.
Title: Re: Low Coil voltage? Ideas
Post by: ccsct203 on September 21, 2009, 08:41:17 PM
Finished the mod yesterday
Took 1 1/2 hours (i'm real picky)
a full 12.4 volts at coils... and yes I feel a slight difference in performance