My son's 78 Chev 4X4 has a frustrating electrical problem.(aren't they all!)
Under acceleration the amp gauge needle drops way down, and the
headlights dim, and the heater fan slows way down.
At idle the needle goes way up, and the headlights become bright, and
the heater fan speeds up to what I figure is a normal speed.
Another twist to the problem is; if you are going along and brake down
firmly the headlights brighten and the fan speeds up to normal. It
doesn't make any difference if you do this in gear or in neutral.
Things done so far:
Had alt tested: It tested good.
Replaced both battery cables
Replaced battery (even though old one tested good)