Before I found out that....I tested the battery as it stands dead cold, at 12.4 volts. Turned headlights on for 1 minute, and voltage loss was down to 12.02.

i know the truck won't start with that low voltage.

i turned headlights back off and voltage climbed slowly back to 12.3 volts after another minute.

If i am confirm I'm doing my pvc testing correctly, my voltage drop test is garbage and will need to buy a new voltmeter, as all my voltage drops are incorrect.

with that being said, I also ordered a new motorcraft sw1951c solenoid (with 3 posts as I still have mechanical fuel pump, and will wire the solenoid up the way I was told, without running a lead wire to the solenoid on the starter, instead, I'll put on the jumper terminal. I'm sure the Chinese solenoid won't last, as it never did in the past....

 

Here's another iteration of the test, note the loose bolt and crap clamped on terminal and eyelet....no way that's only showing .01 resistance.

 

Most all consumer DVOM's have a fine enough scale to measure the resistance. And it is far far more accurate then measuring for Volt drop as you see will the resistance increase before you pick up the volt drop.

 

You are absolutely right...................


Cause you have the meter set on DC Volts instead of Ohms

 

No, it doesn't work that way. The resistance in a circuit like this is inferred, by means of a voltage drop test, because it can't really be measured practically. It's the only way to accurately test excessive resistance in high amperage circuits.

http://www.aa1car.com/library/voltage_drop_testing.htm

"It doesn't take much of an increase in resistance to cause trouble. Let's say a 120 amp alternator operates in a circuit that has a normal resistance of 0.11 ohms. If that resistance were increased to 0.17 ohms because of a bad wiring connection, the alternator's maximum output would be limited to 80 amps. In other words, an increase of only 0.06 ohms (almost nothing!) would reduce the alternator's maximum output by almost a third! Under light load, the drop in charging output might not even be noticeable. But in a high load situation, the alternator wouldn't be able to keep up."

Keep in mind it helps to read the task at the link here for the OP. We're measuring a cable or connection in parallel, with the voltmeter set on its lowest setting. Since voltage always seeks the path of least resistance, any voltage loss will be displayed as a positive number.

(Oftentimes people misunderstand the term "voltage drop", thinking it means the voltage across the battery terminals. That is a specific type of testing, but not what's referred to here.)

 

Get rid of those clamp on battery terminals! Junk.

 

What is the temperature in KY right now. 12.4 volts is a little low for a sealed maintenance free battery, depending. It should still spin the motor OK though.

You want to see 12.80 volts, surface charge removed on a sealed, maintenance free battery. That's at 77° F; turn headlights on for five minutes. Turn off then wait at least 10 minutes before measuring. It should "bounce back" to 12.80 volts.

There is a correction factor applied when temperature is lower, for both charging and open circuit measurement.

 

You are not saying anything I don't know I'v been doing this sort of diagnostic testing for over 4 decades and what do know went to shcool got a masters in this sort of stuff and specialized in tracing QA QC faults for serveral years. Ijust might happen to know a thing or 2 about this sort of stuff.




All you are suggesting is doing the same as has been done that has resulted in NO SOLUTION. Doing the same stuff over and over is not going to fix this. There is a reason to OHM out the cables and connections that will been needed later on to verify other checks.


So instead of jumping to conclusions maybe ask why I asked for this.....
Seriously any time something new is brought this board you lot have not seen or heard of it is the same old crap. You all think you know it all already and have nothing to more to learn........


Oh and BTW standard lead acid batteries generate 2.1Vs per cell, in a standard 12V auto battery the at rest voltage should be right around 12.6V, Not 12.8V. 12.4V is perfectly fine and falls with in serviceability. This battery is NOT a mait free battery, AGM, or other is it is standard low mait group 31 battery.

 

Pulled my starter to make testing easier, I showed absolutely no resistance and voltage drop. What matthew says is to make a jumper between the 2 large posts and run the remote wire to the fenderwell solenoid, is this correct?

 

 

Went back to page 8 and re wired. The small post on the starter gets the jumper to the large post. That eliminates the 10 gauge wire from the fender solenoid altogether.

 

 

All components tested good, to minimize headaches, im wiring in the factory direct drive starter to fender solenoid. I feel like I'm gonna start welding these Chinese solenoids again and I should have the Motorcraft one tomorrow. But i might be able to find out if the Chinese solenoids are the reason it's welding, or maybe the problem lies deeper.

 

 

The $64 dollar question: You later said everything tested good. How did the parts store test the starter? This is very important. Did they just apply power to it and watch it spin? Or did they have a special machine that puts a load on it and makes it work hard?

Spinning the starter without a load on it is practically worthless. You'd catch one that is totally dead, but it wouldn't fault a starter that fails only under load.