Re:1) generic Gremlin speedo cables, 2) diodes in alternators...

[Gremlingts@xxxx]

 1) I would take along the old cable, when or if you decide to go 
cable-hunting. It is almost a certainty the wrong cable will be selected if 
you DON'T take the old part along, it's hard to cross-reference AMC now, and 
with all the changes in engines and trannys they made in the '70s, a sure bet 
it won't be a simple choice! Some parts stores have a generic cable section, 
depending on simply the two ends of the cable housing ( screw on, push-in, 
etc ), so taking the old one along, although that will basically disable the 
car, is a given if you want to get it right the first time. 
2) The diode is simply a one-way electricity "valve", that allows flow in 
one direction, but not another. An alternator produces Alternating current, 
meaning the polarity changes back and forth constantly, like your house 
current. There are kits you can buy, actually, to tap into your alternator's 
pre-diode stage, to run small 110 AC devices off of, as the alternator does 
produce 110 volts AC . The diodes basically "chop" the negative wave off, 
then use several others to "smooth out" the peak voltage to make a fairly 
even 13-14 volt output. That is actually what the "Rectifier" is, is four 
diodes ( in the shape of a box , ends soldered to make a 4-sided square), 
with input on one end, output on two others. That 4-sided circuit is 
predominant in ALL electronic devices, from your digital alarm clock to your 
stereo, as it is the primary means of converting AC into DC voltage and 
current. Anything using DC voltage has to have one of these circuits. So, 
when one goes bad, it may let the current flow the other way, so your 
charging capacity drops or stops, as it's like filling a bucket, then 
emptying it again, doesn't do much good either way! 
The dimly pulsing Alt. light on the dash is related to a bulb issue on 
early cars from '70 or so, and it's also just a characteristic of the 
Motorola charging system, most don't run optimally, I bought a totally 
rebuilt one for my '70 Javelin, and the lights ( headlights, etc. ) STILL 
pulse slightly, so unless I put in an external filter to clean it up the rest 
of the way, I'll just live with it, or change over to a GM alternator. My '74 
Gremlin system hasn't seemed to pulse, except for the light now indicating a 
problem. Anyway, that's my lesson for the day, ya'll have a good week! I'll 
be job hunting....

Jerry
Electronic Repair Technician, 18 years experience
'74 Gremlin, needs repairs.