9400 alternator problems - Page 2 - The Combine Forum
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post #11 of 16 (permalink) Old 11-07-2018, 08:56 AM
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Lets say you are measuring 13.5 to 14.2v (i use 13.8v as a guesstimate) at the batteries with the engine reved up to rated speed. Then you start turning on electrical loads. If you see your voltage dropping off at a certain amount of load then you have a general idea what max output of alternator is, or you have a connection issue to find. As the alternator reaches max output the regulator reaches max voltage forcing level and can't drive voltage higher, or too much voltage drop within alternator. Everything has its limits. As Jeff suggests, you can learn more by testing at the batteries or load side of relays and then right at output terminal of alternator. If voltage reading is low at both places then alternator is just not getting voltage high enough due to max output. If alternator voltage is doing ok (say 13.2v = not ideal but good enough) and battery reading is 12.2v then you have connection issues. Amperage readings are helpful for confirmation and better understanding. Technically speaking, you can figure out the problem without knowing amps but more info is always a good thing.

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post #12 of 16 (permalink) Old 11-07-2018, 03:01 PM
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Originally Posted by kenmb View Post
Lets say you are measuring 13.5 to 14.2v (i use 13.8v as a guesstimate) at the batteries with the engine reved up to rated speed. Then you start turning on electrical loads. If you see your voltage dropping off at a certain amount of load then you have a general idea what max output of alternator is, or you have a connection issue to find. As the alternator reaches max output the regulator reaches max voltage forcing level and can't drive voltage higher, or too much voltage drop within alternator. Everything has its limits. As Jeff suggests, you can learn more by testing at the batteries or load side of relays and then right at output terminal of alternator. If voltage reading is low at both places then alternator is just not getting voltage high enough due to max output. If alternator voltage is doing ok (say 13.2v = not ideal but good enough) and battery reading is 12.2v then you have connection issues. Amperage readings are helpful for confirmation and better understanding. Technically speaking, you can figure out the problem without knowing amps but more info is always a good thing.
I agree with the info in this thread and like Ken says more info is always a good thing. I found it helpful 40 years ago to understand another basic concept of load on your alternator. Not all alternators put out rated amps and they will not do it for hours on end like an all nighter with all the lights on. The little tea cup sized alternators that lots of equipment comes with will only put out that kind of power for a few minutes to recharge the batteries, not to do continuous output running lights, auto steer, monitors etc etc. A helpful little formula that explains so much is the Amps X Volts = Watts or the other way around Amps = Watts divided by Volts. Lots of lights are rated as watts so add them all up. I have some light units that have two 55 watt halogen bulbs in them. That one unit is 110 watts divided by 13.8 volts = 7.97 or call it 8 amps. Now see what starts to happen if your alternator is too small and your voltage drops to 12 volts when running, 110 watts divided by 12 volts = 9.16 amps. As the voltage drops the amp draw actually goes up, which starts a death spiral for an undersized charging system. Just do that exercise and see how many amps you need to run everything. It will shock you! Another problem is that the manufacturers are REALLY CHEAP with copper in their wire sizing. The same problem happens with the formula when you have wire that is too small for the load and distance, which can be significant on big equipment. As length of wire increases, and operating temperature increases, the resistance in a wire goes up and voltage goes down, which again increases amperage. All these little things X 20 or 30 lights and other add ons adds up to the big problem of overload. As was suggested by Jeff who obviously knows what he is talking about from experience!! LED lights decrease the load and help a problem. IIRC he has chimed in on other situations where undersized wire was part of the problem. One of my stories involved a Lex 480 that was starting to melt the F11 ? fuse in the main printed circuit board which ran a bunch of the high draw lights on the front and included some extra side lights for the outer ends of the header. I added 2 more circuits directly off the battery via a disconnect and about an 80 amp circuit breaker. I ran 2 #10 circuits up the top of the cab and connected a big continuous duty solenoid to each circuit to turn on various lights. The signal for the solenoid is the old light switch and wire which now has an easy job of supplying just miliamps of current to energize the solenoid. No more overloading in the main circuit board and the lights are better than ever. However that still takes big power to run. I am led to believe from a reliable source that the standard alternator for a Lexion is special, thus the $1600?? price tag, in that it has silver solder connections and will withstand the high heat from continuous duty and high load. And some ability to do that when the screen and vents are plugged solid with dust!! Blow them out DAILY!! I am convinced we should have liquid cooled alternators on a combine. And sized for the big continuous loads .

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post #13 of 16 (permalink) Old 11-08-2018, 08:59 PM
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These last 2 posts should be taught as standard equipment electrical troubleshooting procedure! Nicely done!
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post #14 of 16 (permalink) Old 11-11-2018, 08:44 AM Thread Starter
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Thanks for all the inputs all where very helpful. I'll keep them in my tool box for when other problems like this come up. The fix was a bad pulley with a place wore letting the belt slip under load. Replaced the pulley with 2 groove pulley everything is working fine now. Thanks again for all the help.
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post #15 of 16 (permalink) Old 11-12-2018, 11:05 AM
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?? Does the 9400 have a shorter motor than the 9500? When I changed my alternator, there is BARELY room for a single groove pulley on the alternator--its smack up against the big radiator fan bearing frame. Maybe 1/4" clearance. In fact, I had to slot the holes holding the alternator frame another 1/4" to get clearance to install the Delco.

Good you got it fixed!
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post #16 of 16 (permalink) Old 06-23-2019, 10:58 PM
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Try to check your relay and circuit breaker by battery, whether it is OK. You have replaced battery and alternator, so maybe the poor contact of battery terminals.
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