Noticed my voltage drops from 13.5 to 14 volts to 12 volts when idling with head lights on and cooling fan running. My radio also starts cutting out intermittently when idle drops to 12 volts at idle. Is this normal on a Powergen alternator? I have read about bearing noises on other posts but have not noticed any. Engine is a 53 Flathead in my 40 coup and it runs fine an have it idling at 750 RPM. Anyone else have this problem?
That’s a lot of draw at idle, I’m going to be the first to say get rid of the electric fan. What does it put out at 2000rpm? Oh and check amperage output. That’s the one that really matters. Sent from my iPhone using H.A.M.B.
Check your pulley ratios. If it’s stock Flathead, you may be able to put a smaller pulley on the alternator with no problem. That’s if the alternator is doing what is supposed to do at it’s given rpm. Bones
I thought about the pulley also. Has it been doing this since installed or something new? It's normal for the voltage gauge to drop a little as you turn on accessories. Do the lights dim when you let off the gas? Battery could be on the way out.
Understand that headlights pull a lot of power, understand that electric fans pull a lot of power, together.....you figure it out, turn one or the other off and see what happens. Turn both off, all is good, you don't have enough generating power to keep up, its that simple.
What’s the alternators rated output? At idle? And at a certain rpm ? Is your battery sized correctly? Is it good? Wiring correct? Clean ? Tight? A fan, lights,and radio are a big draw on a modern car and alt, never mind older stuff that idles low. Do your home work and report back !
The way stators are wound determines how much amperage out put at a given RPM. Take 2 alternators the same size one rated 40 amps the other at 70 amps. The only difference is the stator. The 40 amp will charge more at idle but less at 5,000 rpm the 70 is just the opposite. We tend to buy alternators like cam shafts. If a 90 amp is the same price as a 68 amp we tend to buy the 90 amp. If the cam we need and the cam Warren Johnson runs is the same price what do you buy? Head lights draw 10 amps a good fan draws 15 amps a real good fan draws 20-23 amps. That said most cars do not idle for long periods of time and once off of idle the 90 amp alt. will charge the battery at a high rate. AS stated all ready a pulley change would help. A peace of 10 gauge wire from the back of the alt. to your system would be good.
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