I have a 130 amp output alternator on my 02 F-159. I've added some electrical stuff that has me wondering if my charging system is up to the job at hand. The voltage is from 12.0 to 12.6 volts at times at a warm idle. Other times it has 13.6 volts. I get these readings when the electric fans are on. Should I upgrade the alternator?
Charging question
- Thread starter kaboom10
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The voltage sounds low--it should not be dropping below 13V at idle unless there is an exceptionally high load on the alternator.
What exactly did you add? Have you measured the current draw of the electric stuff you added?
What exactly did you add? Have you measured the current draw of the electric stuff you added?
The biggest load is the dual electric fans. Then there's all the lighting comes directly from the battery. There's several electric guages and an upgraded stereo.
If you goose the throttle does the voltage come up? Could be normal. If you find the specs on your alt it'll be 130 amps at X rpm, which will be higher than idle. Typically expect 30-40% at idle which puts you at 50 amps.
That's why cop cars have HD batteries, even though they aren't ever turned off the electricity runs a deficit at idle at times.
A good compromise might be finding a way to bypass your stereo amp and just use the headunit if you find yourself stuck crawling in hot traffic for a long time.
That's why cop cars have HD batteries, even though they aren't ever turned off the electricity runs a deficit at idle at times.
A good compromise might be finding a way to bypass your stereo amp and just use the headunit if you find yourself stuck crawling in hot traffic for a long time.
It's probably because it's a "Ford F-159" and not an F-150.
Check your battery connections, ground connections and alternator connections for corrosion and make sure they are clean/tight.
I have also seen faulty batteries cause weird voltage readings, could be a bad battery and not the alternator.
The whole charging system needs to be checked out thoroughly.
Check your battery connections, ground connections and alternator connections for corrosion and make sure they are clean/tight.
I have also seen faulty batteries cause weird voltage readings, could be a bad battery and not the alternator.
The whole charging system needs to be checked out thoroughly.
The voltage will be a steady 13.6-13.8 volts above idle. It has a new Optima battery as of a couple of months ago.
Did I call it a 159 again? The cables are original. They look puny to me. I want to go dual battery eventually. I guess I'll go get me some better cables and start building?
And u see them revving above 3500rpm all the time. Designed to work where it will be. I get charging increase just above my 600rpm. It's only got 45k miles but the age of the components are starting to show?
If you restored your stereo to stock you'd probably get your voltage back. Put a voltmeter on your battery after it's been sitting overnight, record the temp, I bet you'll find it's at least 90% charged. (There are tables on google for state of charge at any given temp). It'll be staying charged, I bet, and no action will be required. Being a high quality battery it'll put up with what is very mild abuse.
One little tiny thing you can do is route your amp power cable directly to the big + nut on your alternator. This will save the typically undersized cable coming from the alt to run everything else.
One little tiny thing you can do is route your amp power cable directly to the big + nut on your alternator. This will save the typically undersized cable coming from the alt to run everything else.
The stereo upgrade was just a head unit. I'll go up a size or 2 on the output cable.
That alternator should put out at least 80 amps at idle (the 130 amp Ford 3G alternators do). An upgraded head unit isn't going to consume that much more power, nor will gauges.
Find someone who has a clamp-on DC ammeter (or get one from Sears) and put it on the output of the alternator and see what it reads when the voltage drops below 13V at idle.
Find someone who has a clamp-on DC ammeter (or get one from Sears) and put it on the output of the alternator and see what it reads when the voltage drops below 13V at idle.
I was out without the A/C on and got 13.6-13.8 volts @ idle. I'll ck into that clamp on ammeter. Thanx for the suggestion.
You don't need more amps from a beefier alternator, you need to overdrive it at idle. Use a smaller pulley on it.
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