View Full Version : 91 Sportster turn signal module gone bad

16th April 2010, 20:07
Hey all,
Need some quick wiring help. I have a 91 Sporty that the turn signal module went bad on. Now all I have is emergency flashers all the time. The 90 model didn't have that module, only a flasher switch like one would find on a car. I have the wiring diagrams from the 90 & the 91 but can not for the life of me figure out which or what all wires need to be jumped or crossed to get the lights flashing again. I lost my job last month so I really don't have $130+ to shell out for a new module. No shorts anywhere else in the lines & the signals were intermittent prior to total failure. Is there anyone out there that has ran into this same problem and was able to fix it inexpensively? Or a resident motorcycle electronics tech on board here?

Thanks in advance

17th April 2010, 00:12
Welcome to the forum first. I have a 91 as well but dont think what you are talking about trying can be done. If you where to cross wires it my just activate both sides if you only want the left or right to work. Are all you bulbs working, not burnt out? What state do you live in? I only ask because some states do not require turn signals. You could just unplug them for now.

17th April 2010, 03:11
Hey Spadesluck,
Thanks for the greeting. I live in Georgia and the law isn't really my concern, it's more in the lines of safety really, especially at night. I know it can be done, because I ran across an archived thread or 2 on here but they weren't very clear and they covered like 3 or 4 different years all with different wiring color codes. I'll just have to study the 90 wiring diagram closer I guess.

Cosmo Kramer
17th April 2010, 03:19
Well with wiring/electrical I think just about anything can be done....so I am gonna take a swing at this.....watch out! :laugh

First though....did you try looking on Ebay for a turn signal module? Might be able to find one cheap on there. But if you still want to go with the older flasher style...read on....

Disclaimer: I do not own either model of bikes here and I am only working off some schematics that were given to me from another XLF member...not the actual service manual....so please check my work here to a service manual! ;)

Ok...first some background as I see it....the way these two systems work are completely opposite of eachother. On the 1990 the flasher is the "old school" type and what controls the flash of the light is the turn signal / hazard flasher. From the turn signal switches the ground wire goes to the flasher which dictates when the circuit goes to ground and thus when the light is on. On the 1991 with a turn signal module....the signal wire coming from the turn signal switches (not the ground like in 1990) goes to the turn signal module and the module interrupts the circuit to cause the blinking light.

Now coming from the 1991 turn signal module you have the following wires:

Orange - Power
Black - Ground
Brown - Feed from right Turn signal switch
Violet - Feed from left turn signal switch
White / Brown - Output to right turn signals
White / Violet - Output to left turn signals
White / Green - Output to speedo light

Now for a 1990 turn signal flasher you have just the following wires:

Orange - Power
Green - ground wires coming from both the left and right turn signal switches.

I guess this is what I would do. As I mentioned before...with the old style flasher the turn signals are controled via the ground wire from the switches. So I would take the following wires and "jump" them....or pull/cut them from the connector and directly connect them...which way you do it is your call:

Brown - White/Brown
Violet - White/Violet

Now with the old style flasher you need a power feed....so take the orange wire going to your turn signal module and use that although I would also take the white/green wire for the speedo and splice to that too so your speedo has lights.

Now the bigger challenge will be getting the green wire (ground) from each switch down to the old style flasher. I dont know the direct routing of the ground wire from your switches but more than likely they splice in with a bunch of other grounds. So I would splice into them and run separate ground wires for each to the old style flasher.

Make sense? Does to me...but I think I talked myself into it while writing this! :laugh

Hopefully somebody can read this gibberish and say if it makes sense!

EDIT: Oh yeah!...and welcome to the XLForum from Buffalo, NY!

17th April 2010, 04:07
do the wires from your switches show a ground or a hot when depressed?

17th April 2010, 14:38
Hey Cosmo,
Thanks for your input on this issue. Yes, I have checked eBay, but unfortunately I lost my job last month so I don't have extra cash to spend at the moment. As for your instructions, looks & reads like it just may be what I'm looking for. But as a45junkie mentioned and I forgot to check, is if the switches even go to ground when pressed. Thanks for reminding me a45junkie! I will give this a try and let you know how it works out.


17th April 2010, 17:15
The switches have a common hot wire then go to the modulator to give it a signal to turn on that side. even battery voltage can mess them up.

mine would come on and not flash or not come on.

I replaced the battery and the problems went away.

I bought a turn signal modulator for my 91, I was still back to the same problem.

I changed the battery it was OK. (the battery would start the bike) at any rate put the charger on your system and see if there is any change. also if it has the wrong wattage bulbs they wont work correctly

17th April 2010, 17:58
well if thats the case it will be easy to put a auto type flasher in the circuit and make em flash but you will have to hold down the button the whole time, and you will not have fourways

18th April 2010, 01:07
MAN!! I am SO P!$$*& at myself right now!!! Why is it ALWAYS the simple stuff that comes back to bite me in the you know where?!?! I never even took into consideration the battery. The bike always starts every day no matter the time or the temp. Just need to pull the choke on it in the mornings is all. As soon as I put the charger on it, it went to charging. I will let you all know in the morning how things are going, but if this fails the next step is to follow Cosmo's suggestions. This is me kicking myself in the A$$ %a$$, %a$$, %a$$, %a$$, %a$$, %a$$.


18th April 2010, 02:03
I know your low on cash right now but you might also consider looking around for a motorcycle salvage yard. Here is a link to some Georgia salvage yards (did a quick google search, there are probably more).


Just a thought if other things don't work out.

18th April 2010, 02:21
That list is VERY outdated. There are only 2 on that list that are still in business. Rockdale & Steve's. All others are out of business. But thanks for the input.