Charging issue

[84prspctr]

the whole truck is rewired with a speedway harness. The charge wire looks like 10 gauge maybe a little bigger

 

[PrairieDrifter]

the whole truck is rewired with a speedway harness. The charge wire looks like 10 gauge maybe a little bigger

Battery cables? I would try running at least a thicker charge wire straight to the battery. I can't speak on that harness though.

 

[84prspctr]

I have my alternator charge wire going directly to the battery. I tested voltage again and I was getting 12.35 volts with all the lights on including the off road lights at the alternator, and 12.3 at the battery. So I took a 4 gauge starter cable and put that on to replace the old 10 gauge charge wire going to the battery and moved the voltage sensing wire from the back of the alternator to the distribution block on the starter solenoid, which is where I had the least amount of voltage. It is now charging at 12.5 volts at the battery with all the lights on at idle. When I rev it it will come up but the belt is now squealing real bad, I tightened it as much as I could. It’s a brand new belt I got when I got the alternator.

 

[84prspctr]

With just the regular headlights on I’m getting 13.1-13.27 volts at 500 rpm idle and 14 volts at 2500 rpm

 

[PrairieDrifter]

With just the regular headlights on I’m getting 13.1-13.27 volts at 500 rpm idle and 14 volts at 2500 rpm

Idle should be around 750. It should just need an exciter wire and a charge wire. What's the wiring harness setup for the alt? Wired in properly? There's nothing else to the system. If the belt is squealing there has to be something wrong with alt. Did it squeal before? Tensioned enough?

Do you have a matching pulley set? As in a/c vs non a/c.

 

[84prspctr]

Before putting on the new belt and putting a bigger charge wire and moving the sensing wire to the distribution block it never squeeled. It only does while revving it.

 

[84prspctr]

Tightened the belt more, no more noises. Started it up and it’s charging at 14.6-14.8 at startup then drops down to 14.5. At high idle with all the lights on including bumper lights it’s at 14.5 volts. Once my low idle kicks on it drops to 12.2 with all the lights on, 13.2 with the headlights on and 13.5 just running with nothing. I don’t really want to raise my idle because it runs extremely smooth where it’s at.

 

[KnuckleBuster]

It doesn’t matter if I have the trigger wire plugged in or not, it won’t charge. This one was a brand new one from db electrical. I’m going to have my old alternator tested, I measured the resistance in the battery wire going to the alternator and it’s 0.01 ohms.

You can't accurately check the resistance in that wire with an ohmmeter. If every strand of wire in it is broken except one, it will still test ok. To do an accurate test you need to check voltage drop on the circuit with approximately a 20 amp load.

As far as output goes, it is considered normal if at least 1/2 volt above base voltage with all accessories on and engine speed at 1500 -2000 rpm. Base voltage should be measured at the battery with everything off and surface charge removed.

Good luck!

 

[84prspctr]

Got all the new cables on. 4 gauge cable going from alternator output to battery positive, 4 gauge cable from batt positive to distribution block, voltage sensing wire moved to distribution block, now we’re running 14 volts at 1200 rpm with headlights on. 14.6 volts with no lights on, and 13.4 with off road lights on and headlights at 1200 rpm. Still having issue with alternator putting out low voltage at low idle, with the cam and everything in the engine it likes to idle at 500-600 rpm. I think I will try taking the smaller pulley off a 10si alternator I have and putting it on this 12si to see if it fixes that issue.

 

[PrairieDrifter]

500-600 rpm in gear? Or in neutral? I'd say you're not going to get any better at neutral idle with that rpm. I'm sure you could spin the alt faster and that might help a little. But I don't think you'll be satisfied at that rpm. That's gotta be like 250-300 rpm in gear on the brake?!

 

[SirRobyn0]

I have little to add to the discussion other than no alternator is going to keep up with that load at 500RPM idle. If you wanna run that low of an idle go for it. But your not going to charge or will charge very poorly at that RPM. Your A/C if you have it will suck at that RPM.

 

[big91burb]

I have little to add to the discussion other than no alternator is going to keep up with that load at 500RPM idle. If you wanna run that low of an idle go for it. But your not going to charge or will charge very poorly at that RPM. Your A/C if you have it will suck at that RPM.

Ok throwing in a question. I just put a reman CS130 in my 91 burb. With the lights and AC (only front rear ac not hooked up) the idle drops and lights dim a little. The voltage drops to 12.7ish at idle, and floats between 13 and 14.2 while driving . I don't have a tach but think she idles too low with AC. As far as voltage does this sound right? I will be going through ground and hot wire connections once this southern heat breaks. Last truck was a 76 k30 no AC and had no real charging variables so not sure on the "newer" truck. Thanks in advance

 

[SirRobyn0]

Ok throwing in a question. I just put a reman CS130 in my 91 burb. With the lights and AC (only front rear ac not hooked up) the idle drops and lights dim a little. The voltage drops to 12.7ish at idle, and floats between 13 and 14.2 while driving . I don't have a tach but think she idles too low with AC. As far as voltage does this sound right? I will be going through ground and hot wire connections once this southern heat breaks. Last truck was a 76 k30 no AC and had no real charging variables so not sure on the "newer" truck. Thanks in advance

My answer is, it sounds ok. It's possible that it's not idle air control valve isn't compensating for the addition load as well as it should, but by your numbers it's charging just fine going down the road ok.

At the shop we'd test the alternator by running the engine at about 1,800 RPM and applying a load with a carbon pile load tester. We should see a couple things, one is as you increase load amperage the voltage will drop. Whatever the rated output of the alternator is we should get to that amperage before getting below 13 volts, hopefully a little higher. With little load we should see 14 to 14.6 ideally. These old trucks I'd give a little variance in those numbers, but the bottom line is as long as the voltage isn't dropping below battery voltage at idle, it's keeping the battery charged and your getting decent numbers going down the road I personally wouldn't worry about it. If you really want to pursue it looking over the charging wire and grounds would be a good place to start.

Hopefully that helps.

 

[gmbellew]

Ok throwing in a question. I just put a reman CS130 in my 91 burb. With the lights and AC (only front rear ac not hooked up) the idle drops and lights dim a little. The voltage drops to 12.7ish at idle, and floats between 13 and 14.2 while driving . I don't have a tach but think she idles too low with AC. As far as voltage does this sound right? I will be going through ground and hot wire connections once this southern heat breaks. Last truck was a 76 k30 no AC and had no real charging variables so not sure on the "newer" truck. Thanks in advance

are you measuring at the battery or using the gauge? on my 1990 burb, the gauge reads about half a volt lower than what is shown at the battery with a voltmeter. also, my ECM readout from ALDLDroid for voltage shows what the gauge shows, also about a half a volt lower than the battery. I am not sure where ECM and gauge are pulling the voltage, but there is drop in the system somewhere between there and the battery. under full accessory load (front air, rear air, lights, radio, etc) my ECM reads out ~12.7v at idle when fully warmed up and the battery will show ~13.3v.

 

[big91burb]

Thank you for the replies!! I will\ need to go over the grounds and will be replacing the charge wire to at least a 6g at some point soon. I have a Chinese (shame on me)digital gauge that plugs into the cigarette lighter...... Need to hook up my DMM and run some leads into the cab to see actual. I am glad it sounds ok as I wasn't looking forward to more sweating..... I went through 3 "lifetime warranty"alternators before I got one that worked out the box. And the damn bolt hole was stripped!!! Had to put a bolt nut and lock washer ......what a damn joke!! I plan on getting a better alternator high output soon for when this one takes a ****. Then I'll have a spare. Once again thank you all!