Turn Signals

Turn Signal Tips

My Jeep® uses what is commonly called a 7-wire turn signal system since it uses 7 wires to work.  There are simpler systems out there but they are pretty easy to figure out.

Click this link or the diagram below to see a Flash animation of a typical turn signal system (you’ll need to have Macromedia’s Flash player installed).  Click the left button for a left turn signal, the right button for a right turn, and the 4-way button for 4-way flashers.  Click the Canel button to cancel the signals.  Click the brake pedal with the mouse and hold the mouse button down to “apply” the brakes.  Release the button to turn the brakes off.  This will let you see how one signal can flash while the brake light comes on on the other side.

This will show you how one of these things works and should help if you are trying to troubleshoot your system.  Many folks don’t understand that their turn signal switch can cause problems like brake lights that don’t work right.   View the animation and you’ll see why that’s the case.  The brake lights are routed right through the turn signal switch.  The diagram below shows the contacts in position for a right turn with no brakes applied:

Below are some notes I made when working on my turn signal system.


Total amperage for 4-way blinked lights is 11.7A.
This breaks down into the following:

  • Front: 2A each lamp, 4A total
  • Rear: 3A each side (2 lamps per taillight, 4 lamps total), 6A total (this spec is for my military style tail lights).
  • Signal Lamp in Sparton: 1A
  • Flasher fuse: 9A (used 15A for 4-way test)
  • Flasher: 550 3-prong
  • Sparton Signal unit: 7-wire system
  • One side blink: 5A including Sparton lamp
  • 4-way blink: 11A including Sparton lamp

All amperages shown are approximate, however, 4-way blinked system 11.7A total and front lamp 2.1A readings were taken with Fluke® DMM and are fairly accurate.


Sunday, August 25 2002 6:35 PM

Replaced the ancient “Tung-Sol” 550 flasher can with a fancy little unit from AutoZone. The replacement unit looks like it has a real relay inside of it and has some heft to it. Standard cans were $2 and the fancy one was only $6 so I figured I might as well try it. Supposedly will last 10 times longer than the regular units.

I don’t know if it will last longer (I hope so), BUT, it has *far better* flashing characteristics with a very steady normal flash rate. Old unit flashed very fast. Only problem with this better unit is it flashes correctly even if you have a lamp burned out, there will be no increase in flash speed or change of sound like the regular flasher cans if a lamp burns out.

Replaced original Sparton turn signal unit with the “modern” equivalent: the Signal-Stat® model 900. Had to give up self-cancelling operation (which didn’t work well on the old Sparton anyway so it’s not like I’ll miss it) but I gained 4-way flashing and smooth reliable switching with the new one. Unknown if an NOS Sparton would have worked better. Probably would have worked OK but they are $80 online and I got the Signal-Stat for $46 on sale at NAPA. This was cheaper than J.C. Whitney sells the Signal-Stats for with shipping.

When installing the Signal-Stat, I added a 46 ohm resistor to the pilot light lead to extend the lamp life of the lamp (grain of wheat?) they use for an indicator. Should have been more like a 30 ohm or so, but 46 was all I had and I do NOT want to have to replace that bulb as long as I own the Jeep. Also added a ground wire into their harness and moved the pilot light wire from a bad location outside the case to inside the case and harness.

Note that YOU MUST INSTALL A HIGHER CAPACITY FUSE TO RUN THE 4-WAY FUNCTION. I removed the existing 9A fuse and put in a 15A fuse before running the 4-way flasher circuit. This was not mentioned anywhere in the Signal-Stat instructions. Kind of an important omission. However, I was already aware of this problem from my previous amp readings with the meter (see above). Even with the new flasher can and smaller(?) grain of wheat(?) bulb in the Signal-Stat, total 4-way amperage still reads around 10.5A, and that’s 1.5A over the 9A original fuse. We would have had a positive smoke test for sure.

By the way, the new flasher can is rated at 25A max total. I should be able to add side markers and/or trailer lights in the future without a problem. I used a regular hose clamp to fasten it to the steering column instead of the very flimsy-looking setup they give you.

The Jeep’s flasher harness color codes* are as follows:

  • LF = single yellow wire
  • LR= single green wire
  • RF = dark grey wire in 3-wire plug
  • RR = orange wire in 3-wire plug
  • brake switch power = light grey wire in 3-wire plug
  • flasher load: white wire to flasher socket
  • flasher pilot: black wire to flasher socket

The Signal-Stat’s harness color codes* are as follows:

  • LF = green wire
  • LR= grey wire
  • RF = red wire
  • RR = black wire
  • brake switch power = grey wire with black stripe
  • flasher load: yellow wire
  • flasher pilot: sky blue wire

Therefore, the color* table between the Signal-Stat harness to Jeep harness is as follows:

  • LF = green to yellow
  • LR= grey to green
  • RF = red to dark grey
  • RR = black to orange
  • brake switch power = grey/black to light grey
  • flasher load: yellow to white
  • flasher pilot: sky blue to black

*Keep in mind your color codes could be completely different, so be sure to check yours for differences.