1991 Ford Thunderbird electrical issues

Tiny
MAGA-TBIRD
  • MEMBER
  • 1991 FORD THUNDERBIRD
  • 3.8L
  • 6 CYL
  • TURBO
  • 2WD
  • MANUAL
  • 40,000 MILES
So after sitting for ten years I picked up this mice infested Tbird that needed paint, tires and a battery. The clutch slipped on the way home do to a mouse nest that buggered up the clutch, a bad omen. After replacing the clutch and a good interior cleaning the brake pedal became hard and abs and brake light remained on. After charging the battery and simply turning the key to the test "click" the electric hydraulic pump came on and brakes energized. But soon after the battery died. I discovered a 60 amp constant draw on the battery. When I pulled the headlamp fuse is disappeared. A test drive revealed that when the engine was running the brake pump will not come on and the brakes discharge and the pedal becomes hard and lights come on again. Turning the car off then the key goes into run position with the engine off will charge the brakes again but once again they discharge when is running and brakes being used. The relay seems like a possible malfunctioning part in both cases but i'm a little hesitant to spend the money on parts if im not positive. The headlight switch is also suspect in this vehicle. Thanks for any insight into this ford post abortion product. :)
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Monday, December 29th, 2014 AT 8:41 AM

6 Replies

Tiny
HMAC300
  • EXPERT
Have the abs unit scanned to see if there is a code. A pro will need to do this. I tmay be a bad abs unit or due to the mouse problem they may have ate the wiring as they do that.
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Monday, December 29th, 2014 AT 9:30 AM
Tiny
MAGA-TBIRD
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Kinda makes it tough to get it there since the car has no brakes.
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Tuesday, December 30th, 2014 AT 9:00 AM
Tiny
HMAC300
  • EXPERT
You can always find the source of no brakes like maybe bleeding the system if pad and shoes are good. If abs light is on you just won't have abs the brakes will work.
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Tuesday, December 30th, 2014 AT 10:16 AM
Tiny
MAGA-TBIRD
  • MEMBER
Actually I think the electric hydraulic brake pump is run by a relay that when the key is in the on position not start, but not running it diverts power directly to charge the system. Then after running the relay lets the power cycle through the ignition switch. Seems they did this to minmize all those amps cycling through the ignition seitch and heating up do much on start up. So without the accumulator charged I havent any brakes to speak of. Two feet and two big legs barely slows the car down. I keep going back to the relay but it does click and works on one side of the switch but maybe the other side doesnt connect. They are $60 to replace and I hate throwing parts at a car. Also, it seems like it takes a long time to charge the brakes too. Wonder if thats related too. Maybe a ground on that side of the switch.
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Tuesday, December 30th, 2014 AT 11:52 AM
Tiny
HMAC300
  • EXPERT
Check the fuses and fusible links in pic I'd bet a link is burnt up and not letting relay give power to motor. I have no further comments or suggestions.
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Tuesday, December 30th, 2014 AT 12:01 PM
Tiny
HMAC300
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See pic
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Tuesday, December 30th, 2014 AT 12:02 PM

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