Lights dim at idle
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Joined: Apr 2012
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Lights dim at idle
Hey everyone,
My 96' F150 5.0 had a bad habit of dimming the headlights at idle/in gear and slow the blower motor down quite a bit. I checked the alternator output and at idle was 12.5 volts. At 1000K rpms, it was 14.3 and CCA was 660 which was 10 more than the sticker said it was and the batt is 3 years old. I know the battery is good so i threw another alternator in there. Did the same exact thing. The alternator doesnt put out voltage until it hits a certain rpm. Took that alternator back and put my old one back in and bought a smaller alternator pulley and slighty smaller belt. Runs perfect! Not a single drop of voltage when the high beams are on along with the blower on Hi speed AND my fog lights on. The alternator is now putting out 14.3 volts at 650 rpm's in gear. For anyone having the same issue, here are 2 links. One is for the pulley and the other is for the slighty smaller belt I got from advanced auto. remember, the belt is for a 5.0 Not sure if the 5.8's have the same belt but I dont think they do. You can just ask the parts guy for a belt 1/2" SMALLER than what your truck calls for.
Pulley
Belt
My 96' F150 5.0 had a bad habit of dimming the headlights at idle/in gear and slow the blower motor down quite a bit. I checked the alternator output and at idle was 12.5 volts. At 1000K rpms, it was 14.3 and CCA was 660 which was 10 more than the sticker said it was and the batt is 3 years old. I know the battery is good so i threw another alternator in there. Did the same exact thing. The alternator doesnt put out voltage until it hits a certain rpm. Took that alternator back and put my old one back in and bought a smaller alternator pulley and slighty smaller belt. Runs perfect! Not a single drop of voltage when the high beams are on along with the blower on Hi speed AND my fog lights on. The alternator is now putting out 14.3 volts at 650 rpm's in gear. For anyone having the same issue, here are 2 links. One is for the pulley and the other is for the slighty smaller belt I got from advanced auto. remember, the belt is for a 5.0 Not sure if the 5.8's have the same belt but I dont think they do. You can just ask the parts guy for a belt 1/2" SMALLER than what your truck calls for.
Pulley
Belt