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Old 02-09-2014, 05:19 PM
Augustinaris Augustinaris is offline
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Default Odd Parasitic Battery Draw

I have a problem with my 1988 ford ranger 4x4 2.9L. It is having a very strange parasitic battery draw, which has stumped me.

After sitting over night, a freshly charged, known good battery is completely dead. Below are some tests that I've done:

1) If I disconnect battery, then connect ammeter in series with negative cable, I get about 3 or 4 mA. (non parasitic)

2a) If I run the truck, turn it off, then connect ammeter while disconnecting negative cable(battery never completely disconnected from circuit), and after about 10 mins, there is about a 4.5 AMP draw (very large)
2b) I pulled every fuse/breaker I could find in fuse panel under steering wheel, and Amp draw did NOT change noticeably.
2c) While reading this 4.5 AMP draw, I disconnect the alternator at regulator, and instantly goes down to 0Amps.

3) I brought the Alternator to a Napa, and it tested Good.

4) Battery nonrunning voltage is 12.7V, while running voltage is 14V.

5) Was told to check AC voltage of battery while truck running, and it is about 30.2 V AC.

6) I replaced Negative Battery Cable, and Solenoid to Starter Cable.

7) I unplugged most every electrical connector I could find under the hood to ensure no broken wires/corrosion/water in connections, and all look good.

8) If I disconnect battery and have it sit a while, then connect it back up when I want to start the truck, it starts right up.

If anybody has anything else for me to check, or any suggestions, they would be GREATLY Appreciated!

Thanks!
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Old 02-09-2014, 05:34 PM
fazda93 fazda93 is offline
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Default Re: Odd Parasitic Battery Draw

I would dis-connect the Alternator,and see if the draw goes away.You will have to unplug,and unhook everything,but its a shot.There is a diode bridge in the alternator that converts the AC that it generates to DC.This bridge also acts as an electric "dam" to keep Battery voltage from backing up into the Alt wingdings.If one or more of the diodes are open/shorted it will allow batt voltage to drain back through.As the Alternator is "Hot" all the time,this can occur even when its not running.One would think however that an indicator on the dash would show a charg/discharge problem,but ive seen defective bridges,with no outward indication.This is a shot in the dark,but in the realm of possibility.
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Old 02-10-2014, 03:11 PM
Augustinaris Augustinaris is offline
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Default Re: Odd Parasitic Battery Draw

Quote:
Originally Posted by fazda93 View Post
I would dis-connect the Alternator,and see if the draw goes away.You will have to unplug,and unhook everything,but its a shot.There is a diode bridge in the alternator that converts the AC that it generates to DC.This bridge also acts as an electric "dam" to keep Battery voltage from backing up into the Alt wingdings.If one or more of the diodes are open/shorted it will allow batt voltage to drain back through.As the Alternator is "Hot" all the time,this can occur even when its not running.One would think however that an indicator on the dash would show a charg/discharge problem,but ive seen defective bridges,with no outward indication.This is a shot in the dark,but in the realm of possibility.
I did as you suggested, and surprise, surprise, Battery was connected all night and once I connected the alternator back up in the morning, it started right up. I guess I need to check the diodes more closely on the alternator.
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Old 02-10-2014, 05:54 PM
fazda93 fazda93 is offline
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Default

Quote:
Originally Posted by Augustinaris View Post

I did as you suggested, and surprise, surprise, Battery was connected all night and once I connected the alternator back up in the morning, it started right up. I guess I need to check the diodes more closely on the alternator.
Awsome .. if it's a new Alternator then have them replace it ......
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Old 02-10-2014, 06:59 PM
sheltonfilms sheltonfilms is offline
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Default Re: Odd Parasitic Battery Draw

I would get that replaced asap! One guy had the same issue and it ended up killing every module that didn't have a diode associated with it (PCM i know for sure has one, and either ABS or Airbag modules have one too). Fried his GEM, RAPS, ABS/AIRBAG (whichever one doesn't have the diode).

Wait I just saw you have a late 80s truck. Probably not too many modules on that one.
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