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Disable your '01 and Newer TJ Flasher "Lamp Out" Detector for LED Tail Light Installation
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When Jeep decided to make a change to their electronic flasher circuit for 2001 and newer TJs,
George Gillespie stepped up to the plate. Here is his fix to disable the "Lamp Out" detector
circuit.
(George, Thanks for letting Mesa 4x4 put your solution up.)
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Technical Information:
"The manufacturer of the flasher changed the IC used in the '01 and up version of the flasher. I contacted Atmel with
a documentation request for the new chip, but was told it was proprietary customer-only information. I traced out the
circuit and tried deactivating lamp out detection by cutting traces, but my attempts were unsuccessful. The '01 FSM
turn signal page revealed the hazard switch function was bypassing frequency doubling to allow lamps to cycle at a
normal rate regardless of a lamp out condition.
When depressed, the hazard switch bypasses frequency doubling by taking the L91 contact to ground through the GND contact.
L91 goes to pin 6 of the IC through a 470 ohm resistor. I measured 13.7VDC at pin 6 which turns out to be about 30mA of
current. The Radio Shack 275-241 relay is rated at 1A and fits nicely inside the flasher enclosure.
How it works:
- 12VDC from the IGN contact energizes the relay coil.
- The Normally Open contact closes taking L91 to GND.
- Frequency doubling is disabled.
Turn signals only work when the ignition is on.
The hazard function works normally.
I had a lot of fun working to solve the need to disable the frequency doubling mode of the
flasher. It gave me a chance to fiddle some more with electronics, learn a bit more of the
Visio software program, dig around my Jeep and most of all to contribute to the Jeep community.
I have benefited so much from the great wealth of shared knowledge, it makes me feel good to
think I have contributed, even in a small way."
Simple steps:
1) Remove the electronic flasher, it is located on top of the steering column.
2) Remove the flasher cover, a small screwdriver and some careful prying makes this happen.
3) Go to Radio Shack and get a 275-241 relay, fine tune your soldering skills, and prepare to
make the modification.
4) Your finished product should look something like this:
5) Verify your connections, check for possible short circuits, re-install the cover.
6) Install flasher
You are finished.
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