The alt light on my 66 has started glowing. I noticed it today when the clutch on my 200 4R wouldn't lockup. I have disconnected the TCC from the circuit and the glow gets brighter as engine rpm rises. I have 12volts at the battery not running and 14.5 while the engine is running. Battery is an Optima red top. Alt/reg are stock 66. The voltage at the fuse for the TCC is <10 volts. With the TTC connected and in 2/3/4 gear engagement the light is full bright (I may post this part of the question in the tranny forum). Might a short in the TCC circuit take out the reg or alt? Any thoughts?

I'd suspect you have a wells electronic regulator and the part of the circuit that controls the light has failed. The regulator and alternator are working and charging the car so it can't be anything too serious.

As for the TCC, I'd suggest you take a good look at it before you try using it again.

Peter

I check it all again and I'm getting about 3.5 volts at the battery side of the fuse (fuses are good). This is the circuit that turns on with the ign switch and causes the GEN light to come on when the TCC is engaged. I hooked the TCC to a full time 12 volt fuse and all looks good. The GEN light does not glow or come on. Of course, this isn't the way to run the TCC since it will draw current even when the ign is off (I have a relay that controls the TCC and don't want full time juice to it).

What might cause that circuit to show only 3.5 volts?

In that case, it sounds like there is a bad connection between the fuse and the power source.

I take it it's 3.5V when the TCC is engages and is actually higher when it isn't??

Peter

3.5 is without anything attached to the fuse block.

Trace the power source back and you'll find the source of both problems. The alternator light is turned off by applying 12V to both sides of the bulb. If the regulator side has 12V and the power side drops to 3.5V the light comes on.

Peter