Key off, all fuses in - 12.6
Key on, all fuses in - 5.5
Key on, IGN A pulled - 6.5
Key on, IGN B pulled - 5.5
Key on, IGN A & B pulled 9.4 Dash comes on
Key off, IGN A & B pulled 10.3 climbing
Key off, all fuses in - 10.4 climbing

 

What’s the voltage at the crank fuse during key on but no start?

pull the crank fuse and starter relay and see if anything changes


George

 

.03 V at crank fuse with key on
No change when crank fuse or starter relay are pulled

 

We are at a massive disadvantage because we don't think that we can accurately measure current to find the problem. That said, Do you have a known good battery with side post mount like your blazer that you can swap for a set of measurements to humor me? All your voltages would require 150A+ with a healthy battery. My blazer draws 98 amps during cranking and holds 10.6V. Things would be smoking, fuses would be getting blown. The only cable that is not fused is the black cable from the battery down to the starter. Have you disconnected it at the starter to see what happens?


George

 

What would be an easy way to verify the readings on the clamp?
Not sure about a battery, have to think on that.
I have unhooked the starter a couple times with no changes, but I can do it again as nothing seems to stay the same.

I will try all of them in the morning.

 

maybe key off and headlights on, measure red cable, find out the wattage of the headlamp bulbs, compute the amperage/current.


George

 

Also, clamp one of the load test cables during a test

 

Battery voltage before test 12.6V, during test 12.1V, after test 12.5V. Measured amp draw on battery tester positive lead was 106 amps. Battery again tested good after 10 seconds.
Starter disconnected, key off. Systems not sleeping Both IGN fuses pulled 9.96 V Red wire .92 amps. Black starter wire has .2 amps????
Battery recharged.
Starter disconnected key off, sleeping. both IGN fuses pulled 12.92 V Red wire .21 amps. Black starter wire has .2 amps, both together .33A
Starter disconnected, key off, both IGN fuses in 12.86 V Red wire .17 amps. Black starter wire has .2 amps
Starter disconnected, key on, both IGN fuses in 5.5 V Red wire 7.8 amps. Black starter wire has .2 amps
Starter disconnected, key on, both IGN fuses pulled 9. V Red wire 1.55 amps. Black starter wire has .2 amps
Starter disconnected, key off, sleeping, both IGN fuses pulled 12.3 V Red wire .21. amps. Black starter wire has .2 amps

Going to look at the black starter wire again

Should I go buy another battery?

 

A 1156 bulb (under hood light) draws 1.9 amps with clamp on meter. Sounds about right.

 

Been working all day, I’ll look at this after dinner

George