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Old 07-17-2013, 07:07 PM   #1
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Alternator Help???

I sure hope somebody can help me with this problem. My load/amp meter on the dash has been occasionally going to zero load for a while and then the next time I would look it would show a normal electrical load. A few days ago I drove about 40-50 miles and it never moved off of zero amps and the volt meter on the dash showed about 12 volts also. The tach hasn't worked right since I bought the coach about 3 months ago. Most of the time would show zero RPMs but occasionally would read about 3000 RPMs which is above the governed speed of the Cummins 8.3. So anyway I figured the alternator was the culprit so I removed the Leece/Neville A001090772 and took it to a local repair shop. Got it back today with a new OE regulator and new bearings(the bearings felt a little rough when rotating the shaft by hand). I reinstalled the alternator and it doesn't work. The connections on the alternator are two heavy cables, one positive and one negative and two smaller wires, one for remote sense and one for ign/field. When testing with a multimeter, I see battery voltage on the sense wire and no voltage on the ign/field wire. It is my understanding that this field wire is switched with the key but I don't see any voltage regardless of ignition key position. I haven't been able to locate a fuse anywhere for this wire. I found a connection in the chassis electrical panel labeled "ign to reg" that has three wires attached to it and I do get power there with key in on position.
Something else I thought was strange was that there is a wire labeled "tach" that was taped up in the plastic wire protector at the alternator. looks like it came from factory this way. I thought the tach was supposed to be hooked to one of the three AC taps on this particular alternator. With this not hooked up, I don't understand how I ever got any reading on the tach whether accurate or not.
I'm about to go back out and run a jumper wire to the alternator field and see if it will charge and then I'll try some more research to see why I'm not getting power to that terminal.
I appreciate any input.

I'm not real good on forum posting. I guess you can set up a signature or something that has your info on it but I haven't done that so I'll just type it in here:
1994 Holiday Rambler Navigator
Spartan chassis
300HP Cummins 8.3 free of any electronics
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Old 07-17-2013, 07:27 PM   #2
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If you want to set up a signature line .
When in " User CP " in the blue bar below your welcome and the Google AD.
Grey box on the left hand side, click " Edit Signature " to fill out the info.
All the wiring , gauge and Alt. info I have is for Freightliner Chassis so I'll let the Spartan Chassis members help with your problem.
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Old 07-17-2013, 08:13 PM   #3
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Thanks for the help on the signature Skip. I'll take care of that after I fix the electrical problem.
Also here is an update. I ran a jumper wire from the ign terminal on the alternator straight to positive post on battery then started engine and the alt worked showing about 70 amps on the load meter and still no tach. I checked the voltages on the inverter monitor panel and both chassis and coach batteries show a little over 13 volts with engine running so I assume the battery isolator is closed and charging both chassis and house batteries. That brings up another question. I am slowly learning about this new to me motorhome and it's systems and I found a box labeled "isolator relay delay". It seems like I remember reading on these forums that the isolator closes to tie all batteries together for charging only after the chassis batteries are charged. Is this what the isolator relay delay does? And how long does this normally take because I saw the same voltages on chassis and house batteries only about a minute after starting the engine and I would assume the chassis batteries were somewhat discharged because of the alternator issue.
One more thing. During all these issues, the BATT light on the dash never came on. I just thought of that and turned off the engine and turned key back on without starting and still no BATT light. I pulled bulb and checked it and it is good. I know in my truck with the key on before engine start that light is on. I wonder if not getting power to the terminal at the engine is related.
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Old 07-17-2013, 08:20 PM   #4
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I'm going to guess that this is not the original alternator that was in the coach when it left the factory.

The fact that the ignition wire is working at the chassis box shows the ignition switch is working. The alternator is probably working, it's just that line to activate it is dead. It's got to be somewhere between that box and the alternator. Maybe running a new line?

I don't know why the tach wire is not hooked up. It should be hooked up to an AC post.

The previous owner of my coach had replaced the original alternator with a Leece Neville alternator and botched the wiring in the coach. It took me a long, long time to get things sorted out so that it works properly.

Hope this helps.
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Old 07-17-2013, 08:32 PM   #5
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i have seen a battery isolator go bad OR send all power to the house batteries
your load/amp meter i am sure only reads one set of batteries
so if all of the load is going to the house batteries you well see no load on the meter

seen this on a older ford RV isolator

if you want to know whats really going on install one of
Bogart Engineering Products | Bogart Engineering units
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Old 07-17-2013, 09:56 PM   #6
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The IRD is working ok. They usually kick in after the voltage reaches about 13.2 volts. They often have a delay to allow the engine to stabilize after startup.

Sounds like you are on the path of the missing field connection. Wish I could help with the tach.
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Old 07-17-2013, 11:25 PM   #7
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Dangit!!! I just posted a long update and accidentally hit the backspace key and the stupid computer browser backed up to the last page and lost everything.
I'll try again.
I was curious why the alt/batt idiot light wasn't working so I removed the bulb and checked the socket with a multimeter and with the engine not running and the key switch in the on/run position I saw battery voltage. I don't understand why the bulb doesn't light up but anyway I reinstalled the bulb which now glows dim and started engine. Believe it or not the load meter showed 70 amps and tapered off to about 30 amps after a few minutes. I thought maybe I left the jumper wire that I hooked up earlier on but I went and checked and I did have it disconnected. I ran the engine for about an hour and monitored the load and voltmeters. I turned on lights etc. and watched load increase and voltage remained constant on the analog dash gauge and the digital monitor panel.
I don't understand how a loose dash warning light bulb would prevent the alternator field from being powered, but that seems to be what happened. I'll keep you posted on any changes.
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Old 07-17-2013, 11:44 PM   #8
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That's not an uncommon ocurance in the world of electronics. I almost always disconnect & reconnect all the connectors anywhere near the suspect area if I have a flakey or intermitant problem.
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Old 07-17-2013, 11:59 PM   #9
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Skip426, thanks for the help. I setup some signature info and what is a DSDP?

JIMKATE, I agree something doesn't seem right. The tach should be on an AC tap. I will check my manuals tomorrow. I think I remember seeing in the Spartan manual what alternator was installed.

Terry, That Bogart stuff looks cool.

YC1, Thanks for the reply. Mine never seems to have any delay after start I see load immediately. Tomorrow I plan to hook up that tach wire to an AC tap on the alternator. We'll see what happens.
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Old 07-18-2013, 12:15 AM   #10
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The bulb could be in series with the alternator field. I would have to see a schematic but seems possible.
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Old 07-18-2013, 10:43 AM   #11
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We are going thru about the same problems as you ....

Check, fix and/or replace all grounds in the dash area.

Check, fix and/or replace all grounds that have to do with the alternator and/or voltage regulator. You may need to have another ground from the alternator to the frame added.
You may need to replace the voltage regulator. If you need to do that find the part number and have the local auto parts store look up the part number. Do not worry if it comes off of something like a Ford truck. (The PO replaced with one that cost $100 from an RV place while we got the same one from an auto parts store for $25.)

Check, fix and/or replace the grounds at the batteries. You again may need to add another ground from the batteries to the frame.
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Old 07-18-2013, 11:32 AM   #12
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I have seen alternator circuits where the dash bulb is wired in series with the field voltage. If the bulb is burned out, or not making good contact with the socket, it will lower the voltage to the field so the batteries will not be adequately charged while the engine is running, or won't charge at all if the bulb is open circuit.
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Old 07-18-2013, 02:53 PM   #13
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the older GM alternator circuits are setup this way they use a light in the system
as a floating ground to + to tell the alternator to come on of off line not sure if this is the same
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Old 07-18-2013, 03:10 PM   #14
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I have learned that when the alternator guage reads low, the last thing to check would be the alternator. The first thing to check would be the battery cable connections. A poor battery cable connection will definitely prevent the alternator from doing its job which would result in a low guage reading and because the alternator is still in good shape, no warning light.
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