71 Alternator/ Reg Problems
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From: Mountains of N. Montana
71 Alternator/ Reg Problems
There may be a thread in here on this but I havent found it yet. So here goes... My 71 F 250 4x4's alternator doesnt seem to charge enough at idle speeds to keep the headlights bright. If I have the turn signals on or step on the brake enough to make the brake lights come on, the headlights will dim slightly... momentarily, or in time to the turn flash.. also the heater fan slows down some at idle. This truck is pretty much OE all the way... is there a better alternator and or regulator out there that will cure this? It's got a FE 360 in it. I've never had any problems with it not charging the battery enough for starting issues to happen but the headlights dimming at idle ( @6-700 rpm ) and then coming up to full brightness at a couple hundred rpm higher, is kind of a pain in the butt. Maybe it's just a regulator problem? As far as I know... it's the original from when it was new... same with the alternator... it's been in the family since 71 and I dont remember anyone ever changing much of anything on it except oil, filters, u joints and brakes and it doesnt get driven much except in the winter months, feeding cattle.
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What your describing is pretty normal. You may want to take it to a chain store that checks batteries and charging systems for free, and they might detect an open diode in the alternator (too much ripple current, but is good enough to keep everything working).
Other than the idle speed and belt tension, there is not much more you can do. You may want to experiment with how much idle speed you can stand without it banging into gear or pulling against the brakes at a stoplight(mostly happens with an automatic). You would be surprised how much difference 50 or 100 rpm will make.
Other than the idle speed and belt tension, there is not much more you can do. You may want to experiment with how much idle speed you can stand without it banging into gear or pulling against the brakes at a stoplight(mostly happens with an automatic). You would be surprised how much difference 50 or 100 rpm will make.
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