Electrical Problem again

[Gary Lewis]

David - Sorry for your loss. Travel safely. You are in my prayers.

[PetesPonies]

Yikes, be safe. Things pop up when you don't expect them. Glad you seemed to nail down the problem.

[jdavidsmi]

Thanks for the kind words and payers, got back home late Wednesday evening.

Got the voltage regulator replaced, yesterday and so far all is good. Voltage stayed around 14 volts while the truck was running. And 12.5 or so with the motor off. The dash amp meter always shows a discharge.

But what is really a bummer is the key off short is back. Battery was dead this morning. So back to tracing wires and looking.

David

 

[PetesPonies]

Unhook the alternator one night and see if the battery is still dead in the morning.

[Gary Lewis]

Glad you made it.  And, glad the regulator is working.  

As for the key-off draw, pull the positive battery cable, put a trouble light from the positive post to the battery cable, and then pull all the fuses.  The light should go out, indicating that whatever circuit is the problem is dead.  Start replacing the fuses and when the light comes on you know which one it is.  

[jdavidsmi]

Saturday when I went to look for the key off short the battery was dead again. I put the charger on it and started working on other things. pinion seal replacement, rearview mirror replacement.

Once it warms up a bit I will attempt the short again.

David

[Gary Lewis]

You might want to pull the positive cable to charge the battery.

[jdavidsmi]

I taken the battery completely out, charged it up over the weekend, I'm taking the battery and the alternator down to the parts house and have them tested again. want to make sure I did not damage the battery with the overcharging from the bad regulator.

[Gary Lewis]

Good plan. Bad diodes could cause a drain, and you could blow diodes with the over-voltage problem.

[PetesPonies]

You still didn't pull the alternator wire and let it sit over night to see if it was dead yet? right?

[Gary Lewis]

That's a good point, Pete.  If the alternator is bad and you do my test the light will still be on when all the fuses are pulled.

[ArdWrknTrk]

If you don't have a meter, you have to have them test for backflow not just output.
Even the free Harbor Freight meters have diode test.
It looks like a line with a box and arrow in the middle.

[jdavidsmi]

Did not get into town today, so I put the battery back in and disconnected the alternator. the voltage across the battery this evening was 12.73

I will check tomorrow and see what happen.

David  

[Gary Lewis]

I think you've found the problem.  Better have the alternator tested.  Again.

[ArdWrknTrk]

12.73V is high for a battery at rest.
I'm used to seeing 12.56 or so.

If you do have a meter or self powered test light, simply test from the alternator lead to ground.

Some DMM's will not pass enough current in 'ohms' to get the diodes to block, but a test light or diode function will show that they are bad.

Or just hook the battery back up and wait a half hour, and feel the alternator case.
Is it warrm?
Yeah the diode(s) are bad.

[PetesPonies]

Not if just turned off it isn't. 2.1V is the textbook spec for a cell, thus 12.6V. But the charging is greater, so when you first turn the engine off, the battery will read higher.

[ArdWrknTrk]

Right.
Like I said 12.7x is high if the surface charge is gone.
So, that reading must have been fresh off the charger.

No battery is 'perfect' and I usually see something a little below the ideal for a LA battery.

Regardless, there are any number of ways to figure out if the diodes are bad.

Try figuring out if the 2G "fire plug" has gone south.

[FuzzFace2]

ArdWrknTrk wrote

Right.
Like I said 12.7x is high if the surface charge is gone.
So, that reading must have been fresh off the charger.

No battery is 'perfect' and I usually see something a little below the ideal for a LA battery.

Regardless, there are any number of ways to figure out if the diodes are bad.

Try figuring out if the 2G "fire plug" has gone south.

I thought that was an easy one to figure out no?
https://cimg5.ibsrv.net/gimg/www.ford-trucks.com-vbulletin/2000x1198/80-20171104_171815_3ea9a2879b6917c7e3901d278453fe6aa298c79c.jpg
Dave ----

[Gary Lewis]

I think there’s a lot more wrong than just the connector in that picture. 🙈

[85lebaront2]

Actually on the up to 1987 2G system, the voltage sense for the POS is beyond the fusible links, look at the 1986 EVTM on the website. If it fails, or has a bad connection if the alternator has been replaced with one that has the "fire plug" permanently attached, the alternator will not charge and will promptly destroy itself. Matt blew one on his 86 F150 due to that, fortunately I still had a good one from Darth and was able to help him.

I still say, I want whatever it was the engineers at Ford were on when that was designed, it must have been some "dynomite sheet mon".