Checking for drain
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New User
Joined: May 2004
Posts: 19
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From: Port Orchard, WA
Checking for drain
92 Aerostar, with mucho miles. I have noticed that in the mornings, especially when colder out, when I start driving and let off the gas the ammeter goes down (discharge) sometimes the van will stall. Now normally I can live with this, however today I went to start the van and nothing, just the starter solenoid clicking. I travel frequently and once I left the battery hooked up and told the son to drive it or start it once a week, well he tried and it was dead, nothing. My last trip I disconnected the negative battery cable and told him to hook it up if he needed it and to disconnect it when done. He did, and it started right up for him. He disconnected it and when I came back home 3 weeks later I hooked up the negative cable and it started right up. I am not sure how I would go about checking for a drain, since that is my first thought. Dome lights don't work since I pulled the light years ago (would stay on all the time). This is a beater van but hey it has given me 190,000 miles plus and can't afford to lose it right now. Any help would be appreciated.
Lead Driver
Joined: Sep 2003
Posts: 7,012
Likes: 204
From: SoCal
If you can connect an ammeter between the battery and the negative terminal, you can read the drain current. Then you can start pulling fuses until the drain current stops. This will at least get you started on where to look.
Elder User
Joined: Dec 2004
Posts: 718
Likes: 0
From: North Jersey, New Jersey
If shorted diodes are the cause then a rebuilt alternator is the way to go.
If you have the original Ford alternator the rebuilding parts (including the diode pack) can be purchased from the dealer but the cost of those parts (unless they are the brushes which in your case it is clearly not) can easily go over the cost of a rebuilt unit.
I rebuilt an alt once new bearings brushes and such but it was only for fun and to see how involved it was. It was actually pretty easy.
Then again I have rebuilt electric motors so I guess that helped me out.
You said that you removed the dome light since it wouldn't go off.
Maybe even though the bulbs out something on that dome light circuit is still drawing current?
In any case what the guys said is spot on get an ammeter and do some detective work. Just make sure that the ammeter supports DC current and not only AC.
If you have the original Ford alternator the rebuilding parts (including the diode pack) can be purchased from the dealer but the cost of those parts (unless they are the brushes which in your case it is clearly not) can easily go over the cost of a rebuilt unit.
I rebuilt an alt once new bearings brushes and such but it was only for fun and to see how involved it was. It was actually pretty easy.
Then again I have rebuilt electric motors so I guess that helped me out.
You said that you removed the dome light since it wouldn't go off.
Maybe even though the bulbs out something on that dome light circuit is still drawing current?
In any case what the guys said is spot on get an ammeter and do some detective work. Just make sure that the ammeter supports DC current and not only AC.
Elder User
Joined: Dec 2006
Posts: 830
Likes: 0
From: Kitchener,Ontario,Canada
I'd bet your alternator is on the way out, rectifiers diodes are faulty. This will affect the charging rate of the alternator which is why you get a discharge at low revs. Suggest getting charging circuit checked, could be a simple case of replacement Voltage reg/rectifier unit.
Battery should hold charge for at least a month, the ammeter in series with the battery is a good way to check for unknown discharge. You can also check the battery state with a hydrometer.
Battery should hold charge for at least a month, the ammeter in series with the battery is a good way to check for unknown discharge. You can also check the battery state with a hydrometer.
