voltage is low

[Jeepeater]

with lights radio and hater fan on, my voltage is reading between 10-11v. So bad that sometimes my radio shuts off. When I rev the motor, or start driving, my volts go back up to 14v. Is my alternator going? Loose conection? Where do I start looking?

 

[broncnaz]

Could be the alternator get it checked autozone does it for free. The EB alternator doesnt put out a lot and at idle with everything on its not putting out hardly anything thats why you get low voltage at about 1400rpm I believe the alternator is putting out max amps which for most EB's is only about 42 amp or 60 amps if your real lucky. A lot of people upgrade to 130 amp alternators because the EB alt is barely big enough to run a stock EB. You may also want to check all the grounds and connections make sure they are clean could help you a little.

 

[mtkawboy]

Id have the battery load tested too. Put a voltmeter across the battery and it should have 14+ or so volts running above idle. Previous post is dead on about the altenators. When the lites get brighter when you rev it up its pretty marginal. Might be a combination of both. At least you can eliminate the battery after its tested

 

[Jeepeater]

Forgot to tell you guys its an 87 5.0 motor with 87 alternator as far as I know.

 

[SaddleUp]

Still probably the alternator. It may have a bad diode as I think that will cause low voltage output.

 

[carnage351]

It may also be your heater motor. As electric motors age, the tend to draw more amps. If the motor is old and worn out then it may be drawing 2 to 3 times more amps than it should.

 

[Jeepster]

voltage regulator. I think its in the alt. also maybe diode. have it checked.

 

[airman]

where do you read the 10-11 volts? is this while running? if not what is it while running and then check voltage at the battery while running. I saw you had another post where your fuel gauge stopped working. I agree with a voltage problem but not sure where yet. Now that gauges and radio are giving symptoms you may have a supply problem but you could have a bad ignition switch.

Where are you reading the voltage? Stock wire harness? If you jump it or change batteries does the gas gauge start working again?

 

[iwlbcnu]

Will the radio pulse on/off with the blinking of the turn signal? Mine did that and it was a bad ground from the batt to the body.

 

[RRRAAAYYY2]

If you want grab a volt meter and phone you can get to your truck with and call me at 1-888-214-7774.

 

[Jeepeater]

Yes, the radio shuts off when the turn signal is on. Volts are too low, I would think. Im reading the volts on an aftermarket guage. Im leaning towards the loose ground. because my voltmeter bounces while driving. Would that cause it to drive up to 14v when on the gas though? Lights and heater motor also brighten and speed up when reving motor. The heater motor is also new(chevy conversion).

 

[RT]

Could simply be the alt does'nt turn on until a certain RPM. On mine the alt turns on at about 1400rpm , so when I'm stopped in gear (automatic) the engine rpm is around 600rpm, the crank pulley is about 6"in ,the alt is just under 3" . The 2:1 ratio does'nt get the alt goin' fast enough.

As soon as I hit 700rpm with the motor, I get 14+ volts.

I think we just need a bigger crank pulley. A smaller alt pulley would make it pretty hard to spin with a load. (belt slipping ).

 

[RRRAAAYYY2]

Could simply be the alt does'nt turn on until a certain RPM. On mine the alt turns on at about 1400rpm , so when I'm stopped in gear (automatic) the engine rpm is around 600rpm, the crank pulley is about 6"in ,the alt is just under 3" . The 2:1 ratio does'nt get the alt goin' fast enough.

As soon as I hit 700rpm with the motor, I get 14+ volts.

I think we just need a bigger crank pulley. A smaller alt pulley would make it pretty hard to spin with a load. (belt slipping ).

Smaller alternator pulley is the easiest, cheapest way to go. You are not transferring enough power to worry about belt slip. You can get aftermartket 2" GM pulleys for about $10-$15.
You can also turn your idle up a little bit. 600 seems real low for a carburated small block.

 

[Jeepeater]

Its an 87 5.0 fuel injected motor. what size pulley should that have? I don't remember this problem in the past. You guys think its my pulley size? Is this a common problem?

 

[iwlbcnu]

Of cousre you will have low output at idle. If the radio and all is shutting off, it has to be bad grounds to the body as the battery should carry the acess at that point. Most people replace the factory neg cable and never reconnect the factory ground on the fenderwell as all replacement cables don't have the attachment point.

 

[airman]

what voltage does your gauge say with all of that stuff off at idle. I assume you got your voltage source on the gauge from in the cab likely the the run wire on the ignition?

 

[Jeepeater]

Im pretty sure it reads around 14v with everything off.

 

[RRRAAAYYY2]

Does your alternator have a large plug in the side of it, with two 10 or 8 ga wires, black with orange strip, as well as a smaller 14ga wire? Then another plug in the rear of the alternator with 3 14ga wires? If so then you have a 2G alternator.
With the truck warmed up is the big plug getting really hot to the touch? It is very common for this plug to burn up. But before doing so it causes a major voltage drop (actually its the voltage drop that causes the heat, that causes the eventual fire).
A lot of this would be a lot easier to do over the phone than on the internet, hint, hint.

 

[Jeepeater]

hey rayyyyy. What are the hours I can call? Im at work during the day. 7am-6pm est.

 

[Jeepeater]

Looks like I have exactly what you said rayyyyy. 2G although my wires look to be green and yellow. I have the plug on the side and one on the back. When I turn my key on My volt meter is showing 12volts. Should it be 14?? I had a prooblem with the battery getting drained a few months ago, because my brake lights stayed on. Since then it has been charged but maybe its low?