OK so another newb question, what should mt alternator gauge be reading? I believe i have the stock alternator so it should still work fine correct? the gauge fluctuates a little but usually once i get going it just vibrates on "0." Is that wrong? I mean car fires up and batt never dies so i have to assume the alternator is fine. so is my gauge working?
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what should my alternator gauge read?
- Thread starter Nickrp
- Start date
lowpressure
Jr. Member
you should see somewhere between 12 and 14.5 typically depending on whether or not the voltage regulator is telling it to charge. if your gauge says 0 but you have no problems with the battery dying then i would place a volt meter on the battery while the truck is running and see what volts you read. if it just says 12 try turning on the lights and then retesting. it will most likely read between 13 and 14 plus.
Low pressure is talking about a voltmeter your talking about a amp meter 2 totally different things.
It all depends on draw/condition of the battery. Usualy just after starting the guage will show a +15 or higher reading for a little while until the battery is at full charge again. When your just running around its normal for the gauge to run about 0 as there is little draw on the battery and the alternator is not charging. Turn on lights and stuff and you may see a slight charge on the guage but probably not unless your using more amps than the alternator can put out then it would show a +30 charge.
It all depends on draw/condition of the battery. Usualy just after starting the guage will show a +15 or higher reading for a little while until the battery is at full charge again. When your just running around its normal for the gauge to run about 0 as there is little draw on the battery and the alternator is not charging. Turn on lights and stuff and you may see a slight charge on the guage but probably not unless your using more amps than the alternator can put out then it would show a +30 charge.
airbur
Bronco Guru
My ammeter bounces back and forth regardless of the draw. Alternator going out?
Broncobowsher
Total hack
- Joined
- Jun 4, 2002
- Messages
- 35,507
Ampmeter shows the current flowing in and out of the battery.
the "-" shows a loss, battery discharging
the "+" shows a gain, battery charging
with the engine not running electrical loads should show a "-" reading
start the engine and the gauge will swing to the "+" and shortly return to the "0" mark
Didn't mention, the "0" is a stable condition where the charging system is providing the electrical power to run the vehicle and the battery is fully charged. After a few minutes of running th needle should stabalize around the "0" mark.
The bouncy needle. Not a sign that the charging system is failing. The voltage regulator may not be as smooth as it once was. Flakey grounds, new loads (EFI is bad for a flakey needle as the injectors fire in short pulses).
What the gauge can tell you...
Always showing "+", you have a dieing battery that will not accept a full charge anymore or the voltage regulator is bad (or bad ground or bad sense wire) causing the charging system to overproduce. Very destructive to batteries. The "cooked" battery from water being overcharged. Generally noticed as the fluid level in the battery is low.
Always "-" you are going to have a dead battery very soon. charging system not working or keeping up.
It can also tell you of a failing system. If the gauge shows all is good, but goes "-" when driving around with the headlight and/or wipers on then you know that the charging system is failing. You can drive around all you want with "0" showing, but not with a "-" showing.
Now if someone wired something directly to the battery, then you are hosed. Since whatever is wired to the battery is on the other side of the ampmeter it will show up as the battery charging by the same amount of amps the device is drawing. Do some headlight relays directly to the battery and now the ampmeter will show a charge with the lights on even though the battery is not getting charged.
Ampmeter is a good tool to show the rate of gain or loss of charge to the battery where a volt meter is only useful for the level of charge. If you watch that you are taking more out then what you are putting in you can catch that there will be a problem before the level drops off (low voltage). Where a volt meter is good for knowing how full the tank is but you may not know that you are loosing level until it is a ways down. But the height gauge (volts) is simplier then measuring flow gauge (amps).
Back to the bouncy needle. You are looking at the flow gauge. You may have a bouncy inflow (charge system) or a bouncy outflow (electrical load). Then it could be a combonation of the two. I have done a complete charging system replacment, (alternator, regulator, battery and a complete rewire) and still had a bouncy needle. Putting the factory capacator (condensor) back on the field wire may help stabalize it if all it is the regulator and not the load causing it.
the "-" shows a loss, battery discharging
the "+" shows a gain, battery charging
with the engine not running electrical loads should show a "-" reading
start the engine and the gauge will swing to the "+" and shortly return to the "0" mark
Didn't mention, the "0" is a stable condition where the charging system is providing the electrical power to run the vehicle and the battery is fully charged. After a few minutes of running th needle should stabalize around the "0" mark.
The bouncy needle. Not a sign that the charging system is failing. The voltage regulator may not be as smooth as it once was. Flakey grounds, new loads (EFI is bad for a flakey needle as the injectors fire in short pulses).
What the gauge can tell you...
Always showing "+", you have a dieing battery that will not accept a full charge anymore or the voltage regulator is bad (or bad ground or bad sense wire) causing the charging system to overproduce. Very destructive to batteries. The "cooked" battery from water being overcharged. Generally noticed as the fluid level in the battery is low.
Always "-" you are going to have a dead battery very soon. charging system not working or keeping up.
It can also tell you of a failing system. If the gauge shows all is good, but goes "-" when driving around with the headlight and/or wipers on then you know that the charging system is failing. You can drive around all you want with "0" showing, but not with a "-" showing.
Now if someone wired something directly to the battery, then you are hosed. Since whatever is wired to the battery is on the other side of the ampmeter it will show up as the battery charging by the same amount of amps the device is drawing. Do some headlight relays directly to the battery and now the ampmeter will show a charge with the lights on even though the battery is not getting charged.
Ampmeter is a good tool to show the rate of gain or loss of charge to the battery where a volt meter is only useful for the level of charge. If you watch that you are taking more out then what you are putting in you can catch that there will be a problem before the level drops off (low voltage). Where a volt meter is good for knowing how full the tank is but you may not know that you are loosing level until it is a ways down. But the height gauge (volts) is simplier then measuring flow gauge (amps).
Back to the bouncy needle. You are looking at the flow gauge. You may have a bouncy inflow (charge system) or a bouncy outflow (electrical load). Then it could be a combonation of the two. I have done a complete charging system replacment, (alternator, regulator, battery and a complete rewire) and still had a bouncy needle. Putting the factory capacator (condensor) back on the field wire may help stabalize it if all it is the regulator and not the load causing it.
fastcarkenny
Jr. Member
Alright. Broncobowsher, you are savy. I have my electric fans wired directly to the batery and it does exactly what you are saying. I show a constant 20 amp charge on my amp guage. Where is it safe to wire them with that much load and still show correctly on the amp guage?
fastcarkenny
Jr. Member
thanks in advance for your help!
- Joined
- Aug 23, 2007
- Messages
- 24,344
Wire them to the alternator output.
fastcarkenny
Jr. Member
Isnt the other end of the alternator output connected to the battery post.
It doesnt matter the where stuff is wire into if the battery is being discharged/charged the amp gauge will show it. Its just that if you wired it to the solenoid you might see a little more deflection in the needle. I wouldnt worry about it.
Broncobowsher
Total hack
- Joined
- Jun 4, 2002
- Messages
- 35,507
After it goes through the ampmeter it is.
The ampmeter reads the charge going into and out of the battery. The alternator should feed the electrical demands of a running vehicle. Take the power off the battery terminal on the back of the alternator and you are using power for other things without putting load on the factory electrical system.
fastcarkenny
Jr. Member
I got 2 votes for the output on the alternator...
fastcarkenny
Jr. Member
Thanks guys! That makes sense now! 
- Joined
- Aug 23, 2007
- Messages
- 24,344
Yes but the ammeter is between the alternator and battery.
fastcarkenny
Jr. Member
Gotcha.
chuck
Bronco Guru
If you look at the wiring dia. I think you will find that the Charge wire goes from the Alt. to the battery side of the solenoid. The load wires attach to the same place. That means that the charge to the battery is not monitored by the meter. The charge that feeds the load and the draw from the battery to the load will show up on the amp meter but not the charge to the battery.
fastcarkenny
Jr. Member
That's what I was thinking, and now that I look at the wiring, Chuck is right. It doesn't matter if the load is on the battery post, alternator or solenoid. It indicates the same on the amp guage. A practal test in my garage just now proves it... I had my fans hooked in at the solenoid. I moved it to the 2 other locations and the guage acted the same.
