North American Turbocoupe Organization



charging circuit is draining my battery
kunar Offline
Member
#1
starting last friday, the tbird started having battery drainage issues. it would be completely dead in just a few hours. so tonight i started isolating circuits to find the draw, and it's the charging circuit. there's a blue/green fusible link on the solenoid that splits off into three wires, but i havent traced it farther than that. a little background, i just put a used alternator on the car a few days before this happened. it was charging at about 14.5v after the alternator replacement. i unplugged the alternator during the testing i've done, trying to figure out where the draw is and the draw is still there with the alternator unplugged.

i'm working on finding some wiring diagrams to trace these wires down, but does anybody have any ideas? maybe there's something common that could be causing these issues? can anybody think of any problems the used alternator could have caused?
1987 Turbo Coupe
1987 Ranger 4.0, 4x4
1991 Escort GT
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Pete D Offline
Administrator
#2
Check your PMs
Pete Dunham


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BJL Offline
Moderator
#3
that is split even more times after that.
it goes to the stop/ hazard lamps.power seat. power locks. keyless entry. auto lights. main light switch. courtesy lamps. power mirrors. illuminated entry.

try pulling fuses 4 ,8 ,12 ,& 16 one at a time.
open the door and latch it and hold the door switch in. so you get better readings.
Brian J Larkin
88TC 320k miles
T3, FMIC ,3in stinger exhaust, gillis,
255 walbro, afpr, 5spd swap,spec clutch, sn95 5 lug,.
89 Cougar XR7 3.8SC Auto
95 Ranger Splash 3.0 auto
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kunar Offline
Member
#4
Pete, email sent

Brain, thanks for the heads up. According to the owners manual, that fuse link is only for the charging circuit. It looks like the yellow one is the one that splits off a million different directions. Either way, i already pulled the fuses one at a time, none of them seem to make any difference. Did it all with the door shut to keep the lights off.

edit: i stand corrected. i see in the diagrams brian sent me that the green fusible link does in fact split off sending power to all the places you had mentioned! i'll double check this stuff tomorrow.
1987 Turbo Coupe
1987 Ranger 4.0, 4x4
1991 Escort GT
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Pete D Offline
Administrator
#5
3 emails on the way
Pete Dunham


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Joe F Offline
Posting Freak
#6
Remove the alternator and have it tested; everything I've seen tells me that a shorted positive diode in the alternator will drain the battery, even with the key off.

My 2¢ worth. Hope it helps.
JR's Place - My '87 Turbocoupe
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Jeff K Offline
Administrator
#7
Probably a bad diode in the alternator. Have it tested as Joe suggested.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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kunar Offline
Member
#8
The draw is there with the alternator unplugged. I've got a hunch its probably my rear defrost... I'll find out tonight after work now that I've got an awesome set of wiring diagrams and a good explanation of where that circuit goes (thanks Pete and Brian)
1987 Turbo Coupe
1987 Ranger 4.0, 4x4
1991 Escort GT
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kunar Offline
Member
#9
after a little bit of a vacation (pawleys island, sc) i finally got back to the tbird today. yes, it's definitely the defrost thats causing issues. the switch looks like it sticks on sometimes, and even comes on by its self. ive got the rear defrost unplugged for the time being. with everything reassembled, its drawing 0.08 amps with the key out, a assume this is knay since i know the computer and radio will have a small constant draw. anybody have more detailed info on the rear defrost circuit? why is it being allowed to stay on with the key off and what fuse or circuit breaker controls it?
1987 Turbo Coupe
1987 Ranger 4.0, 4x4
1991 Escort GT
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Jeff K Offline
Administrator
#10
I am 99.5% certain the 86 and 88 defroster wiring is the same.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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