1986 Ford Thunderbird Car is draining battery

Tiny
JESSELEERICH
  • MEMBER
  • 1986 FORD THUNDERBIRD
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 81,000 MILES
I was driving home, my stereo went out, my lights dimmed and at the first red light, my car died. I waited an hour and it started up to get me halfway home before dying at another red light. Went back the next day, replaced the alternator and the battery. It starts up and runs but the battery light is on. The car is draining the battery and is not being generated by the alternator, even though it's new and works. I've heard of something called a TFI module on some 80's Fords, could this be the problem? Any other suggestions?

Thank you
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Tuesday, March 25th, 2008 AT 1:04 PM

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Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
1986 Ford Thunderbird Car is draining battery

Get a test light and disconnect the negative battery cable now put the light between the cable and battery negative post is the light On? If so start removing fuses one at a time -the fuse that turns off the light is the trouble circuit. Then break out the electrical wiring diagram.

In the event you removed all the fuses and the light is still On disconnect the alternator batt. Feed and the connector-if this one turns off the light-the alternator has bad diodes.
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Tuesday, March 25th, 2008 AT 3:23 PM
Tiny
STRATELECASTER
  • MEMBER
  • 2 POSTS
Hey rasmataz,
I've got basically the same problem with my '90 Bird.
Did you notice jesseleerich stated that the alternator is new. Bad diodes in a NEW(not rebuilt/remanufactured) alternator?
I've got NEW alternator, battery, cables, starter relay, starter and all new fuses throughout. Still alternator not charging.
What else could be our problem(s)?
Please excuse the hijack
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Monday, June 16th, 2008 AT 7:05 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Remove connector from the alternator and check for voltage at the light green and red wire while key is at run position- see below


https://www.2carpros.com/forum/automotive_pictures/12900_ford_alty_1.jpg

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Monday, June 16th, 2008 AT 8:05 PM

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