blower fan surges

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Sep 3, 2002 | 11:22 PM

dbarracuda

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blower fan surges

hey guys
The blower fan for the AC and heater surges with the rpm in my 77 f150 w/400. is this normal of is something getting ready to go? i was thinking maybe the blowere fan of the voltage regulator. i just replaced the alt. cause it was whinning.
Thanks

David

Sep 3, 2002 | 11:38 PM

LxMan1

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From: Louisville,Ky.

blower fan surges

Could be a stuck regulator!! It could be way overcharging which will burn up your battery. If you have a volt meter, hook it to the battery while it is running, then rev it up some. You should never get over 14 1/2 volts. If so, replace the regulator. If you don't have a meter, AutoZone can check the truck for you.

Sep 4, 2002 | 08:40 AM

73Custom

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Joined: Apr 2000

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From: SD

blower fan surges

My '73 does the same thing, blower fan slows down at idle and speeds up at 900+ rpm. I've replaced the alt, batt, cables, regulator and checked the wiring, with no change. It's been that way for over 5 years, I've just learned to live with it. The headlights do the same thing...

Marty

Sep 4, 2002 | 11:57 AM

laptopgeek

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From: texarkana, tx

blower fan surges

Heh heh heh....welcome to the world of the mid 70's...Harrison does this too.... even to blinkem lights change with the rpm...too low and they don't blink. Too low and the blower doesn't work.

Sep 4, 2002 | 09:52 PM

Mike W

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Joined: Apr 2002

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From: Central Kali

blower fan surges

A whine in an alternator indicates that one of the diodes is shorted. The blower motor rpm depends on the voltage input. A heavier wire connected close to the alternator would help eliminate some voltage drop. The blower is going to slow some when at idle.

Sep 5, 2002 | 12:18 AM

Torque1st

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blower fan surges

One other thing that all of you gentlemen need to keep in mind:-)

If there is a loose or bad connection anywhere in the alternator or battery connections you can get a condition called "Load Dump" that can build transients as high as 400V on your electrical system. It is kind of like firing your ignition coil, only this time the coil is your alternator windings and the spark plug is all of your electronics etc. This Load Dump transient can blow the diodes in your alternator, even your NEW alternator! It can also fry ignition modules, stereos, electronic voltage regulators, and other things.

When diodes are blown in the alternator, you will get lowered output and voltage that varies with RPM. Kind of like the old generator setups.

Sep 5, 2002 | 12:38 PM

William

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From: Sun River St. George

blower fan surges

I use the biggest battery that will fit in the tray and an 85 AMP one wire alternator. Cables, wires, connections must be in good order. No surges or low power problems, alternator is quiet and I get 14.5 volts consistently at anything over 900 rpm.
William in Atlanta