Well, I'm still having problems with my electrical system. My guages go dim and some of my accessories go dead (clock, radio) when stopped at a light. When I get back up to speed, or if I rev the engine, everything comes back on. Also, when I turn something else on (wipers, heater if it was off, etc.) something that I had on goes dead.
I just had my battery, battery cables, and starter replaced within the past week or so because of this same problem.
I know that I'm taxing my alternator as it is but could there be "intermittent" problems with it :confussed: My mechanic has tested it but can't find anything wrong.
Does anyone have any clue what's going on?
Help!! I know that I've asked this question before but I can't figure this out.
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85 TC Auto
250-280 rwhp or Bust!!!!
mods: Sony HU, Pioneer 6.5" 3-way in the door and Pioneer 6x8 2-way in the rear deck; full 3" exhaust installed(dp, hi-flow cat, 3" MAC mustang GT cat-back)
On a side note, when I'm in Park with my foot on the brake, the speedo reads 10-15mph ?!?!? When the brakes aren't applied the speedo reads ~10mph steady. THis just started happeneing when I noticed the wierd electrical stuff.
I dont know the whole story behind your issues, but have you checked the alternator? If you replaced it are you sure it is of good quality?
That's what I thought it was at first but my mechanic checked it out and says that there's nothing wrong with it unless it's an "incidental" problem.
Since you have an '85, you have an external regulator. These are notorius for going bad and wreaking havoc on the electrical system. Also, check the main plug (black in color and oval shaped) that connects to the wires coming off the alternator. These often develop increased resistance over time (coorosion, etc...) and will burn up along w/ the associated wiring.
I had very similar symptoms when the wiring and alternator went south on my daily driver. If you want a rock solid electrical system, I would do the following:
1) Undo the ground wire at the block and thouroughly clean it and the contact surface.
2) clean or even replace your positive battery cable if the ends are showing significant wear and tear or the battery end does not hold tight to the batt. terminal.
3) remove and clean the positive cable that attaches to your starter. If this corrodes enough it can cause significant hard starts and in the worst case the corrosion can cause a short that will spark during the starting of the car.
4) Clean the terminals on your solenoid and the eyelets from the wiring that attaches to it.
5) MOST IMPORTANT: Do the 3G alternator upgrade! I went w/ the 90 amp unit to save some money and time, and it is like a brand new car. Between the Jeff K Tech article and the various threads on this forum, you should have no problem installing it. Pound for Pound, it was one of the best upgrades I've EVER done to the car.
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1985 T-bird TC, 5Spd, Black (The Project)
1985 T-bird TC, 5Spd, Black (The Project II)
1986 T-bird TC, 5Spd, Black (The Show Car)
1986 T-bird TC, 5Spd, Silver (The Daily Driver)
1989 Mustang GT, 5Spd, Black
Mr. T -How'd the upgrade go?
For me it went well. Jeff K's article was a big help. Even in the dead of winter here in Michigan, I get full juice at idle w/ the blower motor on high, the rear defrost on, my headlights and foglights on, and my radio on. It really worked well.
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1985 T-bird TC, 5Spd, Black (The Project)
1985 T-bird TC, 5Spd, Black (The Project II)
1986 T-bird TC, 5Spd, Black (The Show Car)
1986 T-bird TC, 5Spd, Silver (The Daily Driver)
1989 Mustang GT, 5Spd, Black
The speedo jumping / reading with the car stopped is a sign of electrical noise in the system. BTDT. Likely the regulator, as Mr T said, or possibly a blown diode in the alternator. Could also be a bad batt to frame ground, motor to frame ground, bat batt terminal connections, etc, etc.
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Jeff Korn
88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)
Well, I just got it tested at the Autozone near my house and after they charged the battery they found that the diode in the alternator was bad. When they ran the test it was only pulling 28 amps!!!! Now I need to get a new alternator
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Mr. T - Do you have part numbers for the 90 amp alternator? I might take it in today and need the part numbers ASAP!!!
I actually purchased a kit through PA Performance (
www.pa-performance.com) The kit I purchased was actually a 1 wire alternator kit and 4 guage wire w/ fuse. In hindsight I should have made my own 4 guage wire to save a few bucks. It came w/ a new D-plug and good instructions. Couple their instructions w/ Jeff K's write up, and you are all set.
One thing I did change was that the 1 wire kit is designed to have the voltage sense wire mounted to the stud on the back of the alternator. I wanted it to get a better read on actual battery voltage, so I cut and added a lead to the solenoid stud. Very minor change, and the way it really should be hooked up.
Here are the part #'s and prices I paid:
PA1614 95amp 3G Alt. 1965-93 all w/ 6 groove serpentine pulley $169.00
PA462802B 3G Regulator Plug 1 wire Type $12.95
PA241101 2-Groove Pulley $4.00
PA9904-1 #4 power wire kit Phoenix Gold 31" long 200 amp $31.50
Again, you can hunt save $17.00 right off the bat by swapping your 2 groove pulley off your old alternator (mine was pretty beat up and I did not have access to a pneumatic gun at the time) and finding a D-Plug in the junkyard. Save some more money by making your own main power lead (4 Guage is really overkill for my set-up, but I can always swap this to another car) and find a used alternator in the junkyard. I paid for convenience and new parts. The choice is yours.
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1985 T-bird TC, 5Spd, Black (The Project)
1985 T-bird TC, 5Spd, Black (The Project II)
1986 T-bird TC, 5Spd, Black (The Show Car)
1986 T-bird TC, 5Spd, Silver (The Daily Driver)
1989 Mustang GT, 5Spd, Black