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gunner · 09-19-2016, 02:27 PM

My previous outing a month ago the voltmeter gauge would fluctuate between 12 and 14 volts. I replaced the voltage regulator and everything appeared fixed. I went camping this past week and the problem reoccurred. It would start fluctuating after driving approximately 10 miles. The volt meter would stay at 12 volts for a couple of minutes and then increase to 14 volts. It did this for the two hour drive to the campground and home. When it went down to 12 volts I stopped and verified that I was only getting only 12.3 volts at the Battery. When I came to a stop I was sometimes able to have it jump to 14 volts by revving the engine. It would either be at battery voltage or full alternator output of 14 volts. I did clean all of the connections at the Voltage Regulator at the campground which didn't resolve the problem. Don't understand why it works fine the first 10 miles of driving before acting up. Any suggestions? Also I was using my generator to power the roof air conditioners both times on the way to the campsite and back home the generator would stop after running for approximately 1.5 hours. It would start back up after I got to the campsite or home so I am glad it wasn't the generator voltage regulator. Very frustrating.

tevake · 09-19-2016, 03:13 PM

Gunner, you might want to check your Battery separator/ isolator at the front under the hood. Replacing mine brought the charging voltage into the correct range. Except for when the headlights are on, then the gage drops back to the low 12 volts.

Also I'm wondering if your voltage reg could be at fault. Letting the ful charge thru to recharge low batt, from sitting as well as powering the starter, then shutting down too much once they have recovered.

Purely conjecture on my part. Electrics are all a mystery to me. Just a little less so after dealing with them on my coach.

Engine cooling and electrics issues seem the bane on our coaches.

Keep us posted as you get it sorted.

Cheers Richard

gunner · 09-19-2016, 03:45 PM

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.

WayneG · 09-20-2016, 04:34 AM

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.

gunner · 09-20-2016, 05:13 AM

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.

WayneG · 09-21-2016, 08:34 AM

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.

bkahler · 09-21-2016, 08:49 AM

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

gunner · 09-21-2016, 10:35 AM

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.

gunner · 09-21-2016, 03:00 PM

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.

bkahler · 09-21-2016, 03:13 PM

Quote:

Originally Posted by gunner

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

gunner · 09-21-2016, 03:32 PM

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.

gunner · 09-21-2016, 03:53 PM

Quote:

Originally Posted by bkahler

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.

mayco · 09-22-2016, 05:24 AM

Seems like we've had a rash of self destructing alternators here lately.

PeterH-350LE · 09-22-2016, 05:29 AM

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.

gunner · 09-22-2016, 10:31 AM

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.

bkahler · 09-22-2016, 04:52 PM

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

gunner · 09-23-2016, 05:24 AM

I have already committed to upgrading to 98 amps from my previous 78 amp alternator. It should be repaired and upgraded either today or latest Monday. I hope 98 amps will be sufficient and not get a voltage drop when turning on all of the exterior lights.

mayco · 09-23-2016, 05:43 AM

Gunner, have you converted any of your exterior lights to LEDs? That will help some on the load side. Ive done all my running lights but nothing to my head lights or tail lights. Even when pulling the light switch out to the first position, without headlights, there is a good bit of amp draw on that circuit. One of these days Ill do my headlight conversion.

gunner · 09-23-2016, 09:39 AM

I have changed to LED the top running lights and back up lights. I have not done the turn signal, tail lights or the head lights.

bkahler · 09-23-2016, 04:49 PM

I couldn't find the Lestek alternator in my shop. It could be in the barn and I'll try and look for it sometime this weekend. I may also have some pictures that I took of it and will search for those as well.