ok, ill admit that this is new to me, i know i have mixed them up before.
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charging problem?
- Thread starter Alabama Mike
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Alabama Mike
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OK, several have said I need to rebuild the alternator, While checking wiring is on my list of things to get done today, let me explain further about my problem and then tell me if you still think I need to rebuld alternator, Gen 2 is showing 14.6 volts when running, Battery is showing 12.7 when running, battery is showing 12.7 when truck is off as well, if there was a draw wouldn't the off voltage be much lower? The battery is good and had it had a full charged day before yesterday, my thinking is its loosing its voltage as I crank the truck up since Gen2 is not replacing the juice. I'm still trying to get a grasp on this 24V system and would like to exhaust all avenues of diagnosis before pulling parts and rebuilding, Now don't get me wrong I appreciate your input, But I plan on keeping this old truck a long time and want to learn its ins and outs, Just seems to me GM could have put 1 24v alternator and made things alot easier. Thank everyone of you for your help on helping me learn a little.
While either bulb will work the difference is in the brightness (heat) of the bulb.
The 194 bulb is 3w and goes in the 24v GEN2 circuit. The 168 is a 5w bulb and goes in the 12v GEN1 and other lights.
If you install the 168 5w bulb in the GEN2 socket it will burn almost twice as bright and get hotter. The additional heat will soften and distort the cluster housing. I have seen some cluster housings that have turned brown from all the additional heat.
The reverse happens if you install the 194 in the other sockets. The lower wattage burns less bright and makes the lights harder to see.
You can't just install a 24v alternator and then draw the majority of the 12v electrical needs off of one battery. That creates an imbalance in the system. The alternator will charge the 12v front battery and overcharge (cook) the rear battery that needs no charging. While it may seem like GM complicated the system, it is actually a very simple system. Just takes some understanding.
Now to your problem.
Where are you checking the voltages at the alternators? What terminals and what grounding location.
The biggest issue with the CUCV charging system is clean connections and burnt fusible links.
Check the following fusible links:
Blue GEN2 link at the 24v buss bar behind the rear battery
Blue 12v to GEN2 wire at the 12v diamond shaped 12v buss bar. The red portion of the wire has a white stripe
Thanks for clearing that up. i have a pile of those bulbs, and i just replaced one in my white 28. did not see this particular issue. i cant find any marking on the bulb's either.
Alabama Mike
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OK, I have check all the connections, I'm getting 28-30 volts to the buss bar when running, on the wiring diagram there is a suppressor between the negative bar and the positive bar. my suppressor has the end broken off, will that keep battery 2 from charging?
Edit: I repaired the end and seems nothing has changed. If I'm getting 28-30 at the bar that would tell me both alternators are working, right? what I'm not understanding is where the batteries are getting there feed from!
Edit: I repaired the end and seems nothing has changed. If I'm getting 28-30 at the bar that would tell me both alternators are working, right? what I'm not understanding is where the batteries are getting there feed from!
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Your alternators are working, you must have a dirty connection at the back battery, on the other hand if it turns over to start good that may not be the problem. also check the ground at the back of the motor by the can fuel filter. it has a bolt with a stud to hold the negative cable , it has been known to cause problems.
Alabama Mike
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well I have cleaned all the terminals, tested continuity on all the wires, chased all the wires down and made sure nothing was broken or disconnected, positive buss bar has a good 28-30 volts, small wire coming into the negative side of #2 battery has 14.5, still I can't get #2 battery to show any better than 12.7, and still have Gen2 light glowing, read the TM's today also, They are no help in diagnosis that's for sure.
Are you able to rev the engine slightly to see if the glow of #2 light changes? when running what is the output of #1? i checked one of my trucks today and tried to duplicate your issue. if i dont rev my truck slightly my #1 light wont go out.(energize) when it does go out i only have 13.9 on the front battery(#1) and 14.9 on the #2. 28.8 total. i think my #1 is a little weak but still within range.
I would check you #2 output at the big red wire at the back when running. is it 14v? if not try to energize the alternator manually by probing the two wire plug with a test light to ground. i think the brown wire is the energize wire. sorry you are having so much trouble.
Alabama Mike
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Well, I'll get back on it tomorrow, I've mess with it till I'm completely perplexed today, I do understand now the the reading I was getting on the back of alt #2 was the input from alt #1 and that the other wires coming off the back was at 28V. I understand how there getting the 28V, but if you have 14V or so going in the the back of Gen 2 and 28v or so coming out how can gen 2 charge battery 2? you can change the RPM and nothing changes on mine, I'm trying to read everything I can find to get a better understanding on just how the system works, If I can understand it I can fix it, But understanding it seems to be the biggest problem right now.
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Your 2 12 volt batteries are connected in series to get 24 volts.
Each battery is charged by it's own 12 volt alternator. The only way this can work is with the second alternator having an "isolated ground" so they can be connected in series(by the batteries).
Each alt simply charges 1 battery just like any other auto.
Each battery is charged by it's own 12 volt alternator. The only way this can work is with the second alternator having an "isolated ground" so they can be connected in series(by the batteries).
Each alt simply charges 1 battery just like any other auto.
Alabama Mike
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Doghead, what is the out put of Gen#2? I'm getting 28 volts or so, how can that alt charge a 12v battery? I'm not trying to be difficult, I'm trying to learn how the system works. You have power from Gen1 going in at say 14.5 volts, Gen 2 picks this up and adds to it, producing 28 volts or so, if Gen 2 charges battery 2 where is that voltage coming from?
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It is a 12 volt alt.
If you measure the voltage at the negative and positive studs on the rear of it, you will get the output voltage(12-14V).
Both alts are identical. The drivers side is grounded with a wire. The passenger side is not grounded to the chassis(it is grounded to the rear battery negative terminal only).
When you get a 24 volt measurement, you are using the chassis ground, there by measuring both alts in series.
I always simply tell people to measure each battery(on it's terminals) with the truck off, then with it running. Unless you have a bad wire or battery, those will be your battery voltages and alternator output voltages.
If you measure the voltage at the negative and positive studs on the rear of it, you will get the output voltage(12-14V).
Both alts are identical. The drivers side is grounded with a wire. The passenger side is not grounded to the chassis(it is grounded to the rear battery negative terminal only).
When you get a 24 volt measurement, you are using the chassis ground, there by measuring both alts in series.
I always simply tell people to measure each battery(on it's terminals) with the truck off, then with it running. Unless you have a bad wire or battery, those will be your battery voltages and alternator output voltages.
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Alabama Mike
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after talking with doghead on the phone last night, and with a little explaining on his part, I went back out and tested Gen2 again, and it is indeed bad. My thinking was that the system had to be grounded to the chassis, all other systems I've ever dealt with are. But seems I have run into something I've never seen before. Kinda makes me feel bad now, I spent 4 or 5 hours yesterday cleaning wires and checking continuity and still didn't get it. But thankfully I'm starting to get my head around it now. Thanks to everyone who helped me out I really do appreciate it!!!