Got in the truck about two weeks ago and both batteries were dead.

Charged them up overnight - two days later same thing.

Replaced them with two new 1000 CCA batteries on the weekend. Made sure terminals were clean etc. checked power draw with key off - none. Got in the truck this morning, both new batteries dead.

What could be causing my power drain with key off overnight?:

1.0 Cabin light: (removed bulb already)?
2.0 Cargo light: (have not checked yet, hidden behind my canopy)?
3.0 Bad headlight switch that could cause the above to stay on?
4.0 Bad shorting Altinator/Regulator. Checked altinator - altinator is charging ok.
5.0 Glow Plug Relay Controller Solenoid shorting out? There is always power going to it with the key off under normal operation, unless the solenoid is leaking there should be no power draw.
6.0 Radio - radio would't kill batteries overnight.
7.0 Auxillaries - don't have any.


Again, if you have experienced something like this before, your help would be much appreciated. Otherwise I am starting to pull fuses to find the leak tomorrow.

Seb....

 

Voltage regulator. Unplug it over night and see id it cures the drain problem. If you have serpentine belt then your regulator is inside the computer.. In that case im not sure what to do.. If you have the new body style truckthen check to see if the glove box light stays on! I always take that lightbulb out because it gets the plastic on the dash so hot that it melts And

 

I have the older body style, no serpentine belt, replace altinator and voltage regulator on right fender about a year ago. Pulled all my cab light bulb,ash tray, glove box (still need to check cargo box light hidden behind my canopy)

I will pull the voltage regulator sounds like a good thing to try after I get the new batteries recharged.

Seb....

 

Disconnect both positive battery leads.....using a test light between one lead and the battery post you may/should get a light if there is a drain. Just start pulling fuses till the light goes out then check all items powered by that fuse.

 

This is a sure way to determine voltage loss, great tip.

 

Well, I think I got it solved. Looks like the culprit is the voltage regulator. I pulled all the power leads off the starter solenoid on the right fender and checked them out one at a time with a 12 Volt light. The only circuit that drew power was the Altinator circuit (although it drew very little and hardly lit up the light). As soon as I pulled the plug on the Voltage Regulator - no more leakage.

Frustrating when new parts fail. I just installed a new altinator and voltage regulator about a year ago.

My 91 F350 has about 5 power take-offs from the starter solenoid and since I had the listing of what they did from my owners manual I was able to eliminate them one at at time (Ignition and Fuse Panel, Altinator, Headlight Switch, Emergency Flashers, GlowPlug Relay)

Thanks for the help guys.

Sebastian.

 

Get a borg warner! The grey one that says "SELECT" on top

 

Last Update:

Well, the new voltage regulator did not fix my problem it only improved how quickly my batteries drained. The batteries would hold for a couple of days if I left the truck sitting. The real culprit ended up being the Altinator diodes.

Note the test light check that PLC 7.3 mentioned does not necessarily detect a diode leak as the current quickly drops off after you connect the light. If you are lucky you might see a quick flicker of the light. The light will only stay on if the diodes are totally gone and mine were just minimally leaking current.

Bad Altinator diodes can difficult to diagnose without the proper tester.

After I checked all my other circuits for leakage, I concluded that it had to be the altinator circuit so I got it checked and yes the diodes were going bad.

The frustarting part in all this is I just replaced the diodes in my altinator and my voltage regulator about a year ago so it of course this was the last thing I though was the culprit.

Best of luck,

Seb....

 

I think this is going to be the cause of my drain issue as well. I know my alternator is about done for and not charging worth a crap, acts like bad diodes to me. I think I may look into the 3g swap.