klowninc89
1/2 ton status
ok my 94 suburban volts been dropping down to red at idle in gear while driving. havs a new alt and battery....im confused...i have fram body and engine grounded? any ideas? please help
CK5
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charging issues
- Thread starter klowninc89
- Start date
454Sub
5/8 ton status
Sure the ALT is good? New doesnt mean good. There is a wire on the backside of the ALT, its by itself, its red, see if it is intact. That wire charges the battery.
Jester1
1/2 ton status
Could be a fusible link or bad gauge also. Put a voltmeter on battery while idling and should be making 14+ volts to battery. If not at battery then to post on back of alt. If alt is making 14+ volts but not at battery I suspect wire or connection inbetween.
klowninc89
1/2 ton status
Well its the second alt. Just to be safe...I took it to advance auto and it passed but said battery need charged? How could it be the wire? Fuseable links just go not slowly pop right?
meanboyjr
1/2 ton status
My '76 K5 has the same problem, but intermittently.
At startup with the truck cold, voltmeter reads 14+, regardless of idle. As the truck warms up over 10 minutes or so, volts will drop to around 8 at idle, but will climb back up to 12-14 at speed. I notice this happens more when the weather is wet.
It's really noticeable when I'm running a full load - lights, blower, wipers.
Like I said, it's intermittent. I've double-checked all grounds. Battery is around 4 or 5 years old, alt is less than 2 years old. I replaced the alternator pigtail when I popped in the new alt, as the original was cracked.
I'm wondering if my issue is similar to the OP's. I have not been able to track it down yet.
At startup with the truck cold, voltmeter reads 14+, regardless of idle. As the truck warms up over 10 minutes or so, volts will drop to around 8 at idle, but will climb back up to 12-14 at speed. I notice this happens more when the weather is wet.
It's really noticeable when I'm running a full load - lights, blower, wipers.
Like I said, it's intermittent. I've double-checked all grounds. Battery is around 4 or 5 years old, alt is less than 2 years old. I replaced the alternator pigtail when I popped in the new alt, as the original was cracked.
I'm wondering if my issue is similar to the OP's. I have not been able to track it down yet.
Jester1
1/2 ton status
Copper wire does corrode and can have bad spots in it. Also the crimped ends or bolted ends. Just give it a good look see to make sure all is tight and right. If the jacketing on the wire is suspect then the corrosion can keep electricity from point a to point b. (or at least slow it down to make it look intermitent)
I don't trust their tests. I've had the tests be wrong.
As already mentioned, what's the voltage on the back of the alternator and at the battery with it idling with "no" electrical load? What is it with everything electrical turned on? Should NEVER go below 12V, and normally should be up in the 13V range.
The older GM altenators (not the "one wire" ones) can test "good" on a tester even if one or two of the 3 diodes in the diode trio are bad,it'll still charge,but at reduced output,and sometimes it'll drain the battery dead,if you let it sit a day or more ,the diodes are supposed to prevent the current from grounding out the battery when the engine is off...battery cables that are old and all gangrene inside can restrict the flow of current back to the battery too,and cause low or erratic charging readings,as can bad grounds...so can partially burnt fusible links...or any of the thick red wires at the starter to the fuse block and altenator.......................................................................................................................I've seen more than one Chevy with the big red wire to the altenator get all crispy where they go over the valve cover and get all corroded,and if you have the two wires on the plug at the altenator,the white or tan one is what tells the altenator how much to put out,if its not getting a full 12V signal,it wont put out much of a charge...
Jessie James
1/2 ton status
While this is probably not the case, I had an old truck that was doing this.
Turns out the starter solenoid was not disengaging after I started the motor. The problem is that it then gets spun by the motor and drains your battery at a very high rate.
Turns out the starter solenoid was not disengaging after I started the motor. The problem is that it then gets spun by the motor and drains your battery at a very high rate.
Keep in mind that alot of alterantors dont like to charge below 1500rpm's. If your gauge is reading correctly when driving down the road you may not have a problem at all. This is even a more common problem with high output alternators and they usually have a note that comes with them telling you this.
454Sub
5/8 ton status
Also if your idiot light for the ALT is out, it wont charge below i believe 2k. It needs resistance in one of the plug wires for it to operate correctly. Just learned that in Hot Rod magazine today.
