Question about 1965 Ford Mustang
Have 65 Mustang with 289. Alternator light stays on constant. Battery is good, have replaced alternator and voltage regulator. Engine shuts off immediately when battery cable disconnected. Any help on what to look for next??
The alternator is not producing any power . If it were the engine would run without the battery. Check the wiring on the alternator. It must ave an exciter wire to make it work.
Posted on Oct 07, 2008
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Posted on Jan 02, 2017
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I am seeing a lot of mustangs are having battery draining issues and I wish to share some simple solutions found while working on a friends 03 GT 4.6ltr.
In a quiet area, key switched off, hood up, Listen carefully close to alternator. I heard a high pitched hissing/whistle sound at low volume, came from back of alternator. This sound was the voltage regulator/rectifier staying on when key is off due to faulty diodes inside the voltage regulator/rectifier circuit, can cause battery to go dead after car not ran in about 2-7 days.
After having the alternator tested free at a parts store, test showed alternator was good because the faulty diodes in the alternator did not show up on the test, the machine did not test for faulty drain back issues that were present.
There was battery voltage running at all times through the two-wire connector on back of alternator. Disconnect the battery first for safety and to reduce chance of short circuit. The yellow wire/with white stripe is hot while car is off so I traced this from the 2-wire connector on the alternator then closer towards driver side front fender. Next I cut the Yellow/White Stripe wire, spliced a good connection wire to it and ran it through a hole in the fire-wall to the fusebox(under dash), connected it to a 15a fuse that does not get used but has power when key is turned on but no power when key is off.
The purpose for re-routing the hot wire to the alternator, is to turn off the alternator charging circuit when the key is turned off so it may not run down the battery. I am seeing good results with this fix(or patch) so far. No More Parasitic Battery Drain!
Another fix can be to change the small pulley on the alternator to a larger pulley so the alternator does not spin too fast, putting too much energy through the diodes can cause a charging system to act a fool. So if you have charging issues and have an alternator changed, putting a larger pulley on can make sense turn into saved dollars(especially on high revving engines).
I hope this info helps to solve some draining battery and/or alternator issues.
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