Brake light coil test

Need a little more information. What year sled. Manual start or battery? Original sled or hacked?


Ski Doo didn’t start installing brake lights until 73. Anything prior to that only used head lights and tail lights if you have an unmodified sled.

FYI: All engines that have a fixed coil and revolving magnets (a magneto) generate alternating current AC. Light bulbs on the old sled were set up to work this way. If by chance you have a sled with an electric start, and thus a battery, somewhere in the sled is a rectifier. It turns AC into DC. The DC was used to charge the battery and usually run the lights.

In 1973 and beyond, Ski Doo added brake lights. They initially implemented them by having a switch mounted near the brake mechanism. This switch was set up to activate when the brake was engaged. Most were mounted in housings which allowed for the threaded switch to be moved in and out; this in and out location determined when the switch would close and the brake lights to glow. As brake pads wore, you could adjust the brake cable to take up free play.  It was then necessary to adjust the brake switch accordingly.

So, if your brake lights are illuminated without the lever being moved, a few things could be amok.

--the brake sending switch is out of adjustment/stuck/faulty

- -wires could be chaffed and shorted, allowing voltage to flow to your brake light independent of the switch position.

-- If you have a battery, the rear tail light connector could be attached to something providing constant voltage. i.e. mis wired heated grips, gps, cell phone outlets etc.

So, to answer your question;
 
--If you don't have a battery, you need a functioning coil and a running engine to generate voltage to light a brake bulb.  If the bulb is lit, the coil works.

--Don’t know how a failing coil would cause a brake lights to be lit.

--A faulty/misadjusted switch or shorted/misconnected wires could.


Post what specific sled you’re working on and someone can tell you the style of brake switch to look for. Do you know how to use a multi/ohm meter?  There are specs to check the resistance and voltage output of lighting coils.

OK, looks like I didn’t quite grasp what you were asking in the 1st post.   The year/model info helps.

I looked at a few of the 1976 Elan wiring diagrams posted on line and they show both a lighting coil and a separate coil to power the brakes. This particular diagram was supposed to be good for 76 Elans up to serial number 3013 0399. It shows the lighting coil (not the brake coil) running thru the rectifier and powering the lights/charging the battery.

Also indicates a brake light coil that feeds only the brake lights. It is not rectified.

If indeed the brake light coil has failed, your brake light would not work---no power.

I currently only have pre 1973 shop manuals in my house to look at. I’ll try to get to the later ones to see if there is a resistance/Ohm spec for that coil. I’d guess (I’ll double check) that it should be outputting at least 12v AC, so you could check that immediately with a volt meter.
You mentioned you have a wiring diagram. Here’s what you can do (assuming the diagram you’re looking at is the same one I’m using).

First check the bulb to ensure the brake filament is intact and working. Or install a new one that you know works. Test

Try closing the brake switch by hand with the engine running.

If you have a meter, set it to VAC and connect to the brake light coil output with the engine running. If you have voltage, turn off the engine, switch the multi meter to ohms and check the brake light switch. Measure across the switch to make sure that as you move it from open to closed, the meter goes from infinity to some ohm value. Use the meter to check the switch’s ground to chassis.

If all this checks out, again use the Ohm meter and check for resistance from the very rear tail light housing white wire to the main harness orange and white, and then thru the orange and black wire all the way to the brake switch. You are looking for breaks, lose or corroded connections

   

Good luck

Yep, using the same wiring diagram.

Engine is torn apart right now but I'll have it back together real soon as I am having intermittent spark issues that I have concluded is dirty points.

If I was betting man I am going with a crack in the wiring somewhere. My head lights work which suggests to me the lighting coil is fine.

One thinks deep deep thoughts about this driving to work, shoveling snow, tying flies, standing in the kitchen listening to the wife tell me stuff I should know, etc.

Fantastic info, many thanks.