[Vwdiesel] Starting problem: '85 Jetta 1.6L non-turbo

[W Davis]

Recently, I have had a problem starting my car when
the engine is warm.

When the engine is cold, the car starts right up.

After being driven, for even a short distance, and
after the engine is shut off, it is hard to re-start,
and sometimes will not crank, as if the battery is
weak.

This happens when the glow plug indicator does not
light up, as if the car is warm enough to start
without the glow plugs heating up.

When the car cools down for a bit, the glow plug
indicator light comes on, and the car starts normally.

The load reduction relay seems to get warm.
Could that be the problem?

Many thanks,

William
1985 1.6L Jetta, non-turbo.

PS:
Glow plugs are new, g-plug relay is new, and matched
to the plugs..."fast". 
(Plugs and relay were bought new in a kit.)

Alternator tests good, battery practically brand new.