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TCI problems Yes or No?

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Many times we over look the simple and expect the worst TCI failure. Most ignition failure causes are connection issues and not the TCI. Here are the steps I use to trouble shoot an ignition problem on a first gen with suspected TCI problem.


1. Remove battery and battery compartment.


2. Unplug both connectors from TCI box


3. With a digital ohm meter connect the black neg lead to the black battery cable. Do not connect to frame or chassis for a ground. Now measure with the red lead of ohm meter to a frame bolt or engine bolt. You should have O ohms or slightly higher.The ground connection to chassis is good.Now we are ready to measure TCI connectors.


4. On the smaller 6 pin connector measure the black wire. It should read 0 ohms or slightly higher. This is the gnd output from TCI to the pickup coil center taps. It may be easier to insert red test probe into the back of the connector plug to take these readings. NOTE: The ground comes from the TCI. You won't have a ground connection on the stator side with connector unplugged. The main ground to the TCI comes in on the output connector from the frame and loops through the TCI to the pickup coil input connector then through the pickup coil connector along lower frame next to stator.

5. Now measure the Orange,Gray,White/Red,and White/Green wires one at a time. These are pickup coil inputs to TCI.They should read 115 -125 ohms normal. If you don't have this or loss of one or more the most common cause is connector failure. (see white connector plug along frame above stator and clean contacts).


6. The Black/White wire is the Emergency Inhibit line. If it measure 0 ohms or has a low resistance the bike willl not start. Normally this measurement is done with the battery hooked up via jumper cables and ign switch on. Various sources through energized relays can inhibit this line. Such as emergency killl switch,side stand relay,tilt switch.clutch switch,etc.


7. With battery unhooked lets move to the 8 pin plug. measure the black wire should be 0 ohms system ground.


8. With the battery unhooked move the black lead of ohm meter to the Red + battery cable and turn on ignition switch. We are now going to measure the resistance back through each Primary Ignition coil to the battery positive lead.


9. Measure the Orange,Gray,Yellow, and White wires. Each should read 2.5 to 3 ohms ref the red battery lead.These are the induction output wires that fire the energized ignition coils, The Red/White wire is 13.8 volt supply line and should read 0 ohms.Thats it for the dc continuity test of connections to TCI. The Black/Yellow,Black/Red wires are from the pressure switch and should only be measured with engine running. The pressure sensor converts pressure into voltage which varys the timing advance with changes of pressure caused by rpm increase. These timing changes can be viewed with a Oscilloscope measuring the pickup coil input pulse and the corresponding output pulse for each cylinder.This is not something you need to worry about now.


If all is well to this point and the obvious has been checked including Spark plugs and plug wires it's time to check the TCI. Before removing it (a patience trying task) I would plug in a spare unit. Every first gen owner should have a working spare or know where you can borrow one. If the TCI is defective remove from bike, open the case by removing the 4 phillips screws exposing the soldered side of circuit board. place in oven at 100 degrees for 30 minutes to remove any moisture in module. You can remove any corrosion from solder side of circuit board with gentle strokes of an old tooth brush and an electronic contact cleaning spray. If you have soldering ability and a low wattage iron resolder all connections below the heatsink nuts on the circuit board. These are the contacts leading to the out side connectors. The heatsink nuts hold the switching transistors that fire the ignition coils. Resolder the 3 terminals of each transistor. with a magnifying glass carefully inspect the remaining solder connections on the board. Anything that has a dull color or hairline crack should be resoldered. You have now fixed probably 95 % of TCI failures. Actual componet failures are rare and can only be accomplished by electronic techinicians with specialized desoldering stations and a schematic of the TCI. Not to mention parts availability for a 20 year old technology. Watch used TCI's can be bought on Ebay ocassionally for $50 bucks.


10. The best way to check a TCI is on the bike but I have plans for bench testing later.


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