This is on the 1980 300 cd 617 n/a
Car is the daily driver and needs to go every day.
Lately I have been having a strange starting issue.

Problem:
Lately the car has been turning over real slow. I mean like 6v tractor slow or timing way advanced on a big block slow. The kind of slow you get before the battery starts clicking. But it still somehow starts. Runs fine after starting.

Block heater plugged in and works fine
Glows work fine test fine
New Bosch battery last march
Battery before starting sits at 12.3 volts
Battery with car running and no accessories on is at 13.7 volts
Battery cables are tight

Other observations:
The other night on a long trip the headlights seemed dim. If I turned off the heater blower they got noticeably brighter. Sometimes the heater seems to blow better then others on the same settings. Which had me thinking alt or voltage regulated but I can't consistently replicate the conditions.

Also the car had been starting strong but seems to do this slow thing when it snows. I am thinking maybe moisture from the snow has something to do with it??


Any help would be great my brother already hates this car the last thing I need is for it to leave him stuck at work. My guess is starter or some real weird electrical gremlins. Anything common come to mind?

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1980 300CD - 130,000 Daily Driver
1984 300CD - 325,000 Dad's summer cruiser

1977 K10 - The Grinch - lifted, locked, winch, 37's. Beadlocks.. 379 t Detroit Diesel
1956 Willys Wagon - buick 225 oddfire v6
1982 SJ 410