69 TI Harness

[Lawrence S.]

The TI harness on my 69 L71 seems to be too warm? I really don't know how hot the harness should be? But I have checked the grounds and they seem fine. I can grab the harness and hold it without burning my hand, but it just seems too warm to me? It warms us right after the car starts. I realize this is a vague question but not sure how else to explain the issue?

Thanks

Lawrence

[Richard M.]

Re: 69 TI Harness

Lawrence, It is normal for the harness to get warm. The internal wires are of a special type with integrated resistance for the coil+ connection. I have some notes somewhere with the resistance value which I'll try to find. If you look at the wiring diagram for TI it shows the resistors in the circuit as part of the harness.

It acts similar to a ballast resistor in a points ignition system, but instead of a separate component it's built into the harness wiring. That's why the wire is sheathed in a special white insulation.

Warm is normal, however burning hot is not normal.

Rich

[Lawrence S.]

Re: 69 TI Harness

Ok thanks Rich. Makes me feel better. Thanks again for all the help resolving the issue on the car. Now time to put some miles on the car.

Lawrence

[Richard M.]

Re: 69 TI Harness

Glad to help Lawrence.

I found my harness notes. The coil circuit resistance value in the harness is 0.3 ohms.(R8 in the CSM "Ignition Pulse Amplifier" wiring diagram) With IGN on, not running, the voltage at the coil+ from the TI Module output transistor is typically 2.5 to 4 volts. The current in the circuit is quite high at these values, so the 0.3 ohm series resistance generates a substantial amount of heat. With the engine running, the continuous high current pulses from the AMP generate much heat as well.

The Battery supply to the Amplifier in the harness resistance value is 0.7 ohms. This dropped voltage supplies the Amp as well as the input to the Pickup Coil to generate the timed pulses to the AMP circuit. At CRANK, this resistance is bypassed to supply full Battery voltage to the PU AND the AMP for increased spark at the slow motion of the engine. The Bypass is in the harness PINK wire which is sourced from the Starter Solenoid R terminal.

Rich

[Lawrence S.]

Re: 69 TI Harness

Rich,
I need to check the voltage at the pink wire. As you may recall, that is where I had 3.9 volts a few weeks ago prior to changing out the mangled engine wiring harness. Per your post to me at that time and per your schematic, the bypass voltage should be 12 volts. Currently, when the key is in start position and engine turning over it will not fire, but the instant the key goes from start to on the car fires? It seems like I still have a low voltage that is not being bypassed correctly to the amp? I will check the values per your schematic.
Lawrence

[Richard M.]

Re: 69 TI Harness

Lawrence, That condition, where the engine tries to fire off as the key moves from CRANK to RUN, is a indication of two possible failure conditions...

1 - Very Possible... A defective Pickup Coil circuit. Either the PU wire connections in the distributor, plug or harness, or a defective pickup coil internal winding. I have seen this exact same scenario in my experiences. I recall you repaired bad connections in your PU Coil connectors.

You need to verify again, with 2 terminal plug removed and ohm meter at the dist terminals, that you get 500-700 ohms consistently there, with wiggling the wires to verify. Either way, I feel you should consider a new PU Coil. K&B makes them and can be bought from many of the suppliers. You'll need to remove and totally disassemble the distributor to replace it, or send the distributor out for PU Coil replacement.

2- Possible a defective bypass CRANK circuit(i.e small gauge Pink wire) coming from the Solenoid R Terminal to the TI harness. The Bypass voltage at that circuit should be whatever the battery voltage is during CRANK. Ensure your meter GROUND is good, and use the COIL- as your meter ground and verify it's true engine/chassis ground at COIL-. I have never seen this condition occur in my experiences, but it may be the condition you're seeing. The bypass circuit also powers the TI Module at BAT+ power during crank so ensure all connections to the TI Module are good also.

I would do this as a diagnostic method.... A assistant at the IGN switch key would be needed here. During CRANK, connect a jumper from BAT+ to the bypass small gauge PINK wire circuit directly in the harness to override the SOL R terminal circuit. If engine runs, immediately disconnect the BAT+ jumper and if the engine continues to run, that is then the fault and eliminates the PU Coil as the fault. Don't leave the BAT+ jumper on continuously after the testing and engine run, only during crank.

If engine does not run at all, it narrows down the PU Circuit as the suspect.

Rich

[Lawrence S.]

Re: 69 TI Harness

Rich,
The old harness had the small gauge pink wire from the "R" post at the solenoid, but the new harness has the larger gauge yellow wire connected to the "R" post on the solenoid. I then took that wire clipped the connector that would had gone to the coil, and connected it to he wire connector that connects to the distributor. I clipped the wires and connected them per the AIM. Do I need to retrieve the small gauge pink wire from the old harness and run that from the "R" post to the distributor connector?

Lawrence

[Richard M.]

Re: 69 TI Harness

IIRC They changed the gauge and color to Yellow at some point. If YEL at R terminal goes to the same place as where the PINK wire did at the dist conn as shown below, then you should be fine.

http://tispecialty.com/articles/66-71diagram.htm

[Lawrence S.]

Re: 69 TI Harness

Lawrence, That condition, where the engine tries to fire off as the key moves from CRANK to RUN, is a indication of two possible failure conditions...

1 - Very Possible... A defective Pickup Coil circuit. Either the PU wire connections in the distributor, plug or harness, or a defective pickup coil internal winding. I have seen this exact same scenario in my experiences. I recall you repaired bad connections in your PU Coil connectors.

You need to verify again, with 2 terminal plug removed and ohm meter at the dist terminals, that you get 500-700 ohms consistently there, with wiggling the wires to verify. Either way, I feel you should consider a new PU Coil. K&B makes them and can be bought from many of the suppliers. You'll need to remove and totally disassemble the distributor to replace it, or send the distributor out for PU Coil replacement.

2- Possible a defective bypass CRANK circuit(i.e small gauge Pink wire) coming from the Solenoid R Terminal to the TI harness. The Bypass voltage at that circuit should be whatever the battery voltage is during CRANK. Ensure your meter GROUND is good, and use the COIL- as your meter ground and verify it's true engine/chassis ground at COIL-. I have never seen this condition occur in my experiences, but it may be the condition you're seeing. The bypass circuit also powers the TI Module at BAT+ power during crank so ensure all connections to the TI Module are good also.

I would do this as a diagnostic method.... A assistant at the IGN switch key would be needed here. During CRANK, connect a jumper from BAT+ to the bypass small gauge PINK wire circuit directly in the harness to override the SOL R terminal circuit. If engine runs, immediately disconnect the BAT+ jumper and if the engine continues to run, that is then the fault and eliminates the PU Coil as the fault. Don't leave the BAT+ jumper on continuously after the testing and engine run, only during crank.

If engine does not run at all, it narrows down the PU Circuit as the suspect.

Rich

Rich,

The resistance at the PU coil is 575 ohms during the wiggle test. The "on" voltage at the pink wire is 7.27 volts. The voltage at the pink wire during crank is 9.39 volts. The battery voltage with switch off is 12.55 volts. I have not tested the voltage at battery during crank. Need to do this.
I will try your jumper test and see what happens.
Thanks
Lawrence

[Terry M.]

Re: 69 TI Harness

Rich,

The resistance at the PU coil is 575 ohms during the wiggle test. The "on" voltage at the pink wire is 7.27 volts. The voltage at the pink wire during crank is 9.39 volts. The battery voltage with switch off is 12.55 volts. I have not tested the voltage at battery during crank. Need to do this.
I will try your jumper test and see what happens.
Thanks
Lawrence

I have been debating throwing this out here because I don't want to confuse the issue, however you can take it for what it is worth.

Two years ago the original TI Amplifier on my 1970 failed. (I should be glad it lasted 44 years. Who said the TI system was fragile?) I had purchased one of the first "new & improved" boards in the late 1980s and so in that went. The engine only started upon release of the key; just like yours. I was told that this was a "feature" of this early replacement board, and that it had to do with the current draw of the transistors in this generation of the board.
This Spring I got a current replacement board and installed it. The engine now starts on the first crank.
I can not remember the brands of the different boards I used, but I could look for the paperwork if it is really necessary.
I just pass this on for what it is worth.

[Richard M.]

Re: 69 TI Harness

Rich,

The resistance at the PU coil is 575 ohms during the wiggle test. The "on" voltage at the pink wire is 7.27 volts. The voltage at the pink wire during crank is 9.39 volts. The battery voltage with switch off is 12.55 volts. I have not tested the voltage at battery during crank. Need to do this.
I will try your jumper test and see what happens.
Thanks
Lawrence

Lawrence,

7.27 volts at the Yellow/Pink wire may be typical as you are reading voltage from the IGN switch but through the TI Harness dropping resistance wire as shown in the diagram. However, you should read Battery voltage at the Yellow/Pink wire coming from the SOL R terminal during CRANK. Definitely check BAT+ volts at CRANK directly at the battery. It's possible the 9.39 volts at the Pink wire is all you're getting from it. If so, battery or connections are suspect. Do this check before the jumper test.

I have been debating throwing this out here because I don't want to confuse the issue, however you can take it for what it is worth.

Two years ago the original TI Amplifier on my 1970 failed. (I should be glad it lasted 44 years. Who said the TI system was fragile?) I had purchased one of the first "new & improved" boards in the late 1980s and so in that went. The engine only started upon release of the key; just like yours. I was told that this was a "feature" of this early replacement board, and that it had to do with the current draw of the transistors in this generation of the board.
This Spring I got a current replacement board and installed it. The engine now starts on the first crank.
I can not remember the brands of the different boards I used, but I could look for the paperwork if it is really necessary.
I just pass this on for what it is worth.

Terry, I think you had one of the original M & H modules. Very early modules had issues at high RPM also. Is it metal around the edges and encapsulated in the center with black epoxy? If so, M & H.

In Lawrence's case, his doesn't start, it just tries to fire off as he releases the key to RUN. One spark burst and that's all, no run.

Rich

[Lawrence S.]

Re: 69 TI Harness

I will check and clean the ground wire from the battery.

[Richard M.]

Re: 69 TI Harness

I will check and clean the ground wire from the battery.

Mornin' Lawrence, Yes, and the SOL R terminal too. Seems odd you're only getting ~9 volts. If you move the meter ground to different GND points, including BAT-, does it change? COIL- is the most important GND point, but check others for reference.

I'll be in and out today, readying for a hurricane here on the FL east coast.

[Lawrence S.]

Re: 69 TI Harness

Rich I hope all goes well with Matthew.
Will check different ground points.

[Terry M.]

Re: 69 TI Harness

Terry, I think you had one of the original M & H modules. Very early modules had issues at high RPM also. Is it metal around the edges and encapsulated in the center with black epoxy? If so, M & H.

In Lawrence's case, his doesn't start, it just tries to fire off as he releases the key to RUN. One spark burst and that's all, no run.

Rich

Rich,

I will have to do some checking to determine the configuration of that antique board. The car is not at home until the ceiling is raised in the garage (Which is too long a story to go into here, and way off topic besides.) I was not sure my experience was relevant, and your comments lead me to believe my first hunch was right. Sorry to have intruded.

Best of luck with the weather.