I recently replaced the main positive cable when I was trying to solve the
problem with the starter in my 1983 900S 'sticking'. I tracked down that the
thermo-time switch is allowing current to leak into the wire to the starter
relay coil but getting back to the positive cable...

What I did was buy some heatshrink tubing the right size (about 3/4" or 18
mm diameter) and pushed a length of that over the lug that bolts to the
starter solenoid. It doesn't give a lot of heat protection but what it does
do is shrink just from the radiated heat off the engine (and in my 8V
engine's case, heat from the exhaust manifold too), and that has now almost
fully shrunk down over the back of the lug and the start of the cable
itself.

It isn't going to form any sort of hermetic seal, but it'll assist the
cable's insulation to protect the copper at the end where it's most
susceptible to damage from contaminants and heat as well to some extent.

The original positive lead in my car (not sure if was Saab-OEM or even
original equipment) was braided with some sort of polymer braiding which was
absorbing every spec of oil and any other penetrating liquid that might come
along!

That's definitely a good indicator that there is possibly a high-resistance
connection as the resistance of a connection determines how much it blocks
current flow (and this is what creates the heating as it's the same effect
as a bar radiator).

High-current connections make this more problematic since higher current
means more power (volts x amps = watts since it's a simple DC system) and
more watts means more heating as the connection resistance increases. So
even a small increase in resistance with a very high current can cause a big
heating effect.

Regards,

Craig.

I don't have a feel for how heavy a 4 ga cable is.  Presumably it is as
thick as the original and is copper.  Is it is, the cable you made
should conduct the same amount of current as the original.  Question is
are you making good enough crimped connections between the cable and
the blade to connect to both posts.

Sometims I wish I drive domestic cars.  That's what you pay driving an
import.  A guy said that to me when I complain about prices of parts
for my SAAB's.

You mean the cable itself gets got ?

That's a sure sign of contact resistance. Could be the termination to the cable
itself ( e.g. a crimp terminal gone 'bad' - you have to replace it ) or high
contact resistance at the terminal itself ( clean terminal and re-tighten using
some copper-ease ).

Graham