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Old 09-19-2016, 04:45 PM   #43
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1984 34.5' Airstream 345
Greenville , Ohio
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I installed a new Isolator last year and had no problems, installed a new voltage regulator a month ago after seeing the fluctuations my previous trip and drove approximately 60 miles with no problems, in fact previous to changing the voltage regulator my voltage would drop down to 12 volts when I turned on the headlights after I installed the new voltage regulator the voltage stayed at 14 volts. Now it is starting the fluctuations again.
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Old 09-20-2016, 05:34 AM   #44
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1984 27' Airstream 270
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Depending on what alternator you have, it may be that the field or sense wire giving you problems. There are many online discussions on this topic. For a quickie, the field wire gets the alternator field "kick started" when you start the engine and the RPMs are low. The field wire can be hooked up in various ways, usually through a resistor wire or light bulb to the ignition switch.
The sense wire is used to adjust the output voltage to a proper level for your electrical system. I have seen this wire attached in all kinds of wrong ways. One wrong way is to tie it to the output of the alternator, but that will set the voltage to that point, and then any voltage droop in the system beyond that will not be sensed. GM's method is to tie it to the battery connection on the starter, giving a more accurate compensation for droop. With all the various configurations in a Airstream, it could be tied on anywhere.
The fact that it happens after driving for a while could be your alternator may be overloaded and causing heat problems. Mine would overheat due to high load and I found that it was not the load doing the overheating, it was belt slip due to a wrong pulley-belt combination. (Always keep your OEM pulley if you do a swap) I had to go to a alternator shop to get a replacement pulley and the overheating problem went away.
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Old 09-20-2016, 06:13 AM   #45
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1984 34.5' Airstream 345
Greenville , Ohio
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I have made no changes prior to these fluctuations. Changed Voltage Regulator to possibly correct, it did improve voltage output with load (headlights and lights on). When these fluctuations occur the only load on alternator is battery charging and ignition, no other accessories are on. I did clean the terminals and tightened the alternator belt when I got to the campsite with no improvements. I believe your explanation of the field wire should be something I need to investigate. Is there anything in the internal components of the alternator that also could be causing this for example failing diodes etc. Every time I start the engine when cold the charging circuit goes to 14 volts something with heat I believe is causing this.
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Old 09-21-2016, 09:34 AM   #46
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The normal voltage from the alternator should be about 14 volts. Unless you have a older alternator, 1960's? the voltage regulator is built into the alternator, along with the rectifiers.
This is approximately what is in my 84, it uses a resistor wire in place of the lamp on the field connection.
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Old 09-21-2016, 09:49 AM   #47
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Wayne,

Just FYI, one of the upgrades that Airstream provided was higher amp output alternator by Lestek that used an external regulator. I've seen several rigs with this combination.

Brad
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Old 09-21-2016, 11:35 AM   #48
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My system uses an external voltage regulator, which is actually one that is used in Ford vehicles. I have taken my Alternator to a repair shop, they are to test it and let me know what repairs are needed plus what would it take to upgrade it from 78 amps to approximate 100 amps.
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Old 09-21-2016, 04:00 PM   #49
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My alternator is completely shot, the stator is burned up, the armature shaft bearing surfaces are galled consequently I decided to have it completely rebuilt changing the output amperage from 78 to 98. One thing that is somewhat confusing the alternator has a internal voltage regulator and also uses the external Ford voltage regulator. I am going to have to trace the wiring to see how the external regulator is used in the circuit, it could just be used as a relay to trigger the charging circuit of the Alternator. If someone has a wiring diagram of this circuit that would be great.
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Old 09-21-2016, 04:13 PM   #50
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Quote:
Originally Posted by gunner View Post
My alternator is completely shot, the stator is burned up, the armature shaft bearing surfaces are galled consequently I decided to have it completely rebuilt changing the output amperage from 78 to 98. One thing that is somewhat confusing the alternator has a internal voltage regulator and also uses the external Ford voltage regulator. I am going to have to trace the wiring to see how the external regulator is used in the circuit, it could just be used as a relay to trigger the charging circuit of the Alternator. If someone has a wiring diagram of this circuit that would be great.
Gunner, I may have the Lestek alternator laying around somewhere in my shop. If I can find it you're welcome to it.

Brad
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Old 09-21-2016, 04:32 PM   #51
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You may want to look at the orientation of the male blade terminals on the Lestec alternator. If the flat of the blades are oriented in-line with the diameter of the alternator it has an internal regulator, if the flats are located in the direction of the width (front to back) of the alternator it has an external regulator.
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Old 09-21-2016, 04:53 PM   #52
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Gunner, I may have the Lestek alternator laying around somewhere in my shop. If I can find it you're welcome to it.

Brad
You wouldn't happen to know what Amperage Lestek Alternator Airstream upgraded to. The reason I am asking is that I am upgrading the one I have to 98 amps and I am wondering if Airstream increased to even higher amperage than the 98.
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Old 09-22-2016, 06:24 AM   #53
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Seems like we've had a rash of self destructing alternators here lately.
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Old 09-22-2016, 06:29 AM   #54
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I replaced the one the previous owner put in because of the same issues Gunner has. That fixed the fluctuation, but it still drops down to 12.5 all lit up. Using the turn signal will add some more pain.
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Old 09-22-2016, 11:31 AM   #55
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I traced my wires coming from the external voltage regulator to the front of the engine, found they were not attached to anything and haven't been used. My purchase of a new voltage regulator was for naught. Someone prior to my purchasing this Motorhome must have switched to a new alternator with an internal voltage regulator. I eliminated the wiring and external voltage regulator, every wire removed helps with cleaning up the wiring harness.
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Old 09-22-2016, 05:52 PM   #56
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For some reason 140 amps comes to mind on the Lestek. I'm going to look for it this evening, if I find it I'll post the info.

I upgraded my Argosy alternator to a 140 am CS-144 GM alternator. It was almost a direct bolt in swap. Had to bend a tab slightly and enlarge a couple of holes. I can provide details if desired.

Brad
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