Eliminate BDM modules?

[Lamar]

My 2004 BD Chopper has no spark at the plugs and won't light up the test light out of the module. This started after my battery died. It cranks fine with new battery. Mechanic came by and said eliminate all the BD computer "stuff" and put a Crane ignition wired direct to the harness. Could it be that simple?

 

[Moespeeds]

Yes, you can very easily eliminate the EHC from the ignition system in the bike. Install the ignition system of your choice, or keep the stock ignition, and simply power it up from a fused connection, either through a separate switch, or through an aftermarket sportster style key switch. The key is to isolate the ignition system from the EHC, if you look at a wiring diagram for a min it should be clear. I would also install a plunger type button on the starter, as the START function is also run through the EHC. The problem is that your lights and blinkers are still controlled by the EHC, so as it goes bad you will lose those functions as well. The only complete remedy is to rewire the entire bike with a stock harness, install a Wire Plus, or a PDM from Big Dog.

 

[Peckerwood]

I've been running my ignition on a seperate circuit (15 amp) as a quick and temporary fix for a failing ehc for over a year now. Start button on handlebar switch works just fine, have a simple high quality toggle switch to power it up mounted next to oil filler neck. It really IS that simple.

 

[Moespeeds]

Here's a link back in 2009 when I did mine. Unfortunately the pics are all gone, but it should help a little.

http://www.bigdogbiker.com/forums/how/8318-how-bypass-your-ehc-power-your-ignition.html

 

[Moespeeds]

Here's a great wiring diagram if you ever need to bypass components.

 

[Moespeeds]

Here's a modified diagram showing just what you need to worry about on your Big Dog.

I left the headlight circuit in there because if you bypass the headlight, ignition, and add a plunger to the starter you will always be able to get the bike home in the event of a total EHC failure. If you gotta have a hi/low just drill a hole in the back of your headlight bucket and mount a little toggle switch right there. In the event that you are keeping the stock ignition, ignore the crane part and just run the IG power to the ignition and the coil. Make sure you cut any other wires going from the stock ignition module to the EHC.

 

[2004BC]

Great schematic Moespeeds!!! Old school simple! I have an Amen frame I'm putting a shovel in and I still have a page out of an old 70's Easyrider that has a similar simple chopper wiring schematic like your Amen one. It really is that simple . How and why did wiring get so complicated when it's not REALLY necessary???? On an exposed to the elements, high heat, high vibration application simple is usually better!

 

[Lamar]

wow, thanks guys. I found a diagram while searching this site that gave the 2004 EHC idiot lights. When I crank mine around, the ignition idiot light goes red, no other lights come on. By any chance, it is not as simple as just replacing the points that I may have burned up when I left the ignition on, dead battery, etc.? I tried taking off the ignition cover, but quickly realized I wasn't the guy for this job when I saw a sealed insert with a wire comimg out, and put the cover back on...I need a big block Chevy to play with....

 

[Moespeeds]

That sealed insert is gonna be your cam sensor. It's a HD part and easy to replace, just search it here.

 

[Th3InfamousI]

wow, thanks guys. I found a diagram while searching this site that gave the 2004 EHC idiot lights. When I crank mine around, the ignition idiot light goes red, no other lights come on. By any chance, it is not as simple as just replacing the points that I may have burned up when I left the ignition on, dead battery, etc.? I tried taking off the ignition cover, but quickly realized I wasn't the guy for this job when I saw a sealed insert with a wire comimg out, and put the cover back on...I need a big block Chevy to play with....

I got an 04 as well. I got the EHC sitting on my workbench, not because it doesn't work. If it turns out that you need one its for sale.


Anyways...That red ignition light is good! When you turn the key that ignition light SHOULD illuminate! Which it sounds like you are getting! :up: When it's cranking does the Thunderheart Igntion light flicker?


I read you removed the points cover, did you happen to unscrew the two screws and take the sensor out? You have to put it back in the EXACT spot as that will mess up your timing. Most likely won't start.

If you didn't move the cam sensor grab a multimeter and check to see if your getting power to the coils when you hit start so we can rule out a bad coil.

If it is not your coil, and you didn't move your cam sensor then you can grab a multimeter and test your cam sensor. Do you have the stock exhaust or aftermarket? Heat has been known to destroy the sensor when the exhaust runs around it.

 

[Lamar]

Th3InfamousI, the light flickers when cranking, I didn't remove the cam sensor, it wasn't what I was expecting (I was expecting to see points behind a points cover) so I put the cover right back on. I will have to get a multimeter, don't have one, but the coild are tough to get to, so is the ignition switch, and it looks like the cover is part of the motor mount and I don't have an allen wrench big enough, so I kinda stopped here.

I assume I will plug the coil wire into the multimeter to check for life, although I think I will just try my test light first.

I still have stock exhaust

 

[Lamar]

Th3InfamousI, the light flickers when cranking, I didn't remove the cam sensor, it wasn't what I was expecting (I was expecting to see points behind a points cover) so I put the cover right back on. I will have to get a multimeter, don't have one, but the coild are tough to get to, so is the ignition switch, and it looks like the cover is part of the motor mount and I don't have an allen wrench big enough, so I kinda stopped here.

I assume I will plug the coil wire into the multimeter to check for life, although I think I will just try my test light first.

I still have stock exhaust

 

[Lamar]

FYI - when the ignition switch is on, the lights all work, turn signals and flashers work

 

[Lamar]

more - under the tank, there are harness wires leading to the ignition/coil area, red, yellow, orange and black, the yellow and red light up with the test light, black doesn't (assume ground) and orange didn't on first try, but that could be because I got tired of slipping with the test light ice pick point and needed to stop bleeding.