Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

It just keeps getting better....

After rebuilding my rear window motors and putting it all back together now I have some parasitic draw on the battery.

While I had the car apart I forgot and left my keys in the ignition. Ignition was not on, just the key was in the slot. That is what I assumed killed my original battery. Since my original would not take enough of a charge to come back to life I just got a new battery. Now I'm finding that the new battery is discharging faster than it is charging.

So what could it be? If all I did was remove the rear window motors and reinstall I don't see how that can be related. I tried putting my multimeter inline between the negative post and the negative cable and it's not showing any drain but If I put a test light inline between the post and the negative cable it does blink like something is running.

Any ideas?


  • just to see I disconnected the motors (fortunately you can get to them via the speakers) but the drain continues. Must be something else.
  • I've been burned before by the obvious stuff even replacing parts that didn't need to be replaced. It might be already something you did but double check the little stuff. Map lights, Under hood/trunk lights.
  • Hood light has been disconnected for years (car shows and such). I don't have visor lights or a trunk light. I checked the glove box light and it was not hot so I don't think that's it. I hate to start pulling fuses.
  • I think now it is the alternator. With the negative bat cable removed I can put a test light between the negative terminal and the negative cable and the test light strobes. If I disconnect the alternator from the voltage regulator and then use the test light I get one flash and then it goes dark. I'm thinking that flash is just some residual current.

    Reading online others have reported a bad diode in the alternator makes it leak power back through the alternator and into the bracket causing the discharge. So until I get a chance to get a new alternator I can just disconnect it when not in use.

    Now I am left to wonder what caused the alternator to go bad while I was working on the rear windows?
  • Murphy's Law?

    Good to hear you are making progress.
  • It sounds like your voltage regulator has finally gone out. IF your battery is draining and there is no clear culprit, charge your battery back up with the alternator completely disconnected, both plugs. When the car sits every piece of metal gets cold on the engine and disconnecting the alternator ensures a battery draining voltage regulator will allow the alternator to cool down too. When the battery is completely charged plug the alternator back in (alternator and voltage regulator). Wait a couple of hours and take your hand and wrap it around the alternator in the area the voltage regulator is bolted to the alternator. If that area of the alternator is hot or very warm you need to replace the voltage regulator AND BRUSHES.

    Now, finding a parts store that carries the regulator and brushes may be difficult. I used to get mine at Napa. The brushes are probably very worn and replacing a regulator without doing the brushes is a waste of time.

    If you like the easier route you can just replace the alternator if you like because you'll get a new regulator and brushes with it. BE SURE you compare the alternator with the replacement when you are at the parts counter. SOME rebuilds have the plugs on the alternator turned in the direction OTHER vehicles need them in which will make plugging your alternator harness into the alternator impossible without pulling the wiring across the alternator.
  • Constant holding of power window buttons in either the up or down position when the motors have the windows all the way up or all the way down can fry a voltage regulator.
  • Got the alternator out this morning and took it down for a core exchange for another Motorcraft. Should be here on Monday and I'll be back in business. Would cycling the window motors when not connected to the regulator fry the VR? As I recall that was the last thing I did before the battery as dead a few days later.
  • alternator is swapped out and lik2gadd you were right, they did have the case rotated about 90 degrees but it all still fit and I didn't feel like fussing with it anymore.

    Lets add it all up:
    6 1/4-20 nuts to replace window motor bushings 2.00
    Crappy Radio Shack multimeter 20.00
    Window regulator that I didn't need 85.00
    Window guide rod mounts that I did need 100.00
    New battery that I probably did not need 145.00
    Rebuilt alternator that I did need 220.00

    Crusin' in my 5.0 with the top pulled back so my hair can blow...priceless

  • Bill,,,,, You got to Live it!
  • Thats supposed to say "Love" it!
  • Glad to hear you got it going!

    Working on cars can get expensive. A WARNING about 1/4-20 nuts in the window motors, I have been told in years and years past that the little $7.00 package of "HELP" Products 3 nylon grommets is worth the investment when fixing Ford power windows.

    (see picture)

    The 1/4-20 nuts DO NOT GIVE when a window is rolled up or down to its limits and when rolled to its extents can cause glass breakage. I think that may be more common in vehicles with window frames though, but be careful anyway. I have always used the nylon parts when repairing my malfunctioning window motors, cleaned all of the old trash and grease out of the motor gear assemblies and repacked the areas with new grease.

    I'm not sure if cycling the windows like you asked would cause the voltage regulator to fail. Years back a friend "ratcheting" (unlock,lock,unlock,lock and on and on) the power door locks in my brother's Grand Marquis fried a voltage regulator. I have had regulators drain batteries in the past, probably from age, and just replaced the regulators and brushes and fixed charging problems. The brushes were hard to locate last time (my first choice for parts being Napa). The last alternator draining the battery problem that I had was different, I had a parts car here so I did a 10 minute alternator swap and cured my problem.
    Ford Window Motor Inserts.jpg
    576 x 345 - 25K
Sign In or Register to comment.