| Alternator/Isolator/Battery Problems/Questions [message #247443] |
Mon, 14 April 2014 20:22  |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
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Senior Member |
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The 76 Palm Beach has one 12v Engine batt up front and 2 6v golf cart house batts by the onan. Has functioned well for years.
After a recent 1000 mile trip (I assume all batts are fully charged now) After the coach was parked a few days the engine batt was dead and the house batts barely had enough juice to start the onan.
Started the onan then started the 455- Noticed that the amp meter was registering almost 60 amps and it continued to read 30+ amps after a 15 mile drive. I assumed the high amp output was because all batts were so low. The ampmeter reading finally dropped to near zero but remained positive.
With the engine NOT running I had 12+ volts at three terminals on the isolator. I assumed the isolator had gone south.
With the batteries charged and the alt working I took another 1200 mile trip. Mid trip I installed a new isolator and discovered that without the engine running and with the alt wire disconnected from the isolator I get a 9v+ reading on the wire.
So now I'm thinking the alternator/regulator is bad.
Back home and the current situation is:
Engine NOT running
Isolator readings:Alt terminal 12.24v Disconnected Alt wire 9.16v
Engine batt terminal=12.64v
House batt terminal=11.77v
With engine running and alt wire attached to isolator:
Alt terminal= 16.45v
Engine batt terminal= 15.5v
House batt terminal=15+v
While taking these readings with the engine running I discovered the alt wire is very hot.
Some where along the way the alt light stopped working- I changed the bulb but I think the contacts may be defective.
So, is the easy answer install a new alternator because the output is too high? Or are there other things to check first?
Thanks for the input.
I'm confident that Ken B. will have a solution in less time than it took me to explain the problem.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: Alternator/Isolator/Battery Problems/Questions [message #247637 is a reply to message #247455] |
Wed, 16 April 2014 17:21  |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
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Senior Member |
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Ken,
I took the readings per your instructions. At step 1 the alt was putting out over 16 volts.
I removed the alt took it to Auto Zone it failed the test on their machine. They replaced the alternator under the warranty.
New alternator also puts out 16 volts. The GOOD bulb in the alternator indicator does not light when key is turned on before starting.
Voltage at the alt wire connecting to the gauge cluster in the dash is 0 with key off 12+ with key on 14+ with engine running. So I assume the bulb not lighting is a problem with gauge cluster circuit board or contact points on light slot on the board.
Isolator readings are as anticipated from your flow chart except that the alt wire when disconnected from isolator with engine not running still reads 12+ volts.
Isolator is new- alternator is rebuilt-
How does one verify that the sense wire is functioning? How does the light failure affect the sense wire system?
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: Alternator/Isolator/Battery Problems/Questions [message #247638 is a reply to message #247637] |
Wed, 16 April 2014 17:26 |
Otterwan
Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...
Karma: 0
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Gene - I just had a nearly identical problem in my 1976 Royale. I have a digital volt meter installed, and I noticed at speed it was reading over 16 volts and at idle 15. I removed the alterntor a took it in for testing. On their tester it was putting out 16.8 volts.
Long story short I replaced it and all is well. All other charging system components were fine.
1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
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| Re: Alternator/Isolator/Battery Problems/Questions [message #247641 is a reply to message #247638] |
Wed, 16 April 2014 18:06 |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
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Senior Member |
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David,
It's certainly possible that I just got a defective rebuilt alternator.
I can replace it again. But that won't solve my sense wire/alt light issue. I'd like to get it all working properly at one time.
Have you removed the galley cabinet from the parts coach yet? I still need a GOOD one. The ones I have found so far are not as good as my original. It seems that the stove vent leaks and the water runs to the rear and settles in the back corner of those cabinets and rots the back and rear end panel.
Thanks for the input.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: Alternator/Isolator/Battery Problems/Questions [message #247642 is a reply to message #247641] |
Wed, 16 April 2014 18:24 |
Otterwan
Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...
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Gene - Sounds like the replacement alternator was bad as well. I got mine from NAPA, and so far it is working fine. I haven't removed the cabinet from the coach. I'll take a look at the back corners and see if there is any rot. I doubt it, as the Palm Beach was under cover for the 16 years it sat idle.
1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
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| Re: Alternator/Isolator/Battery Problems/Questions [message #247649 is a reply to message #247443] |
Wed, 16 April 2014 19:10 |
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WildBill
Messages: 232
Registered: January 2014
Karma: 1
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I would look for a voltage drop between the key and the #2 terminal on the alternator.. In cases where we wanted a higher voltage to the battery To be higher I would place a resistor to reduce voltage to the #2 terminal on alternator to make it charge at a higher voltage. The no. 1 terminal just turns the alternator. You can actually run a jumper from alternator battery positive to the #2 terminal and the regulator will charge to designed regulator voltage. You could also run it to while side battery on the isolator or the house side of the isolator. Whatever you want if you are happy with voltages. I would source off vehicle battery or straight off the alternator.
[Updated on: Thu, 17 April 2014 11:36] Report message to a moderator |
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| Re: [GMCnet] Alternator/Isolator/Battery Problems/Questions [message #247650 is a reply to message #247641] |
Wed, 16 April 2014 19:09 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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gene did you consider this
*DIM ALTERNATOR LIGHT - FUSE-*
There is one other condition that can cause the symptom of a dimly lit
idiot lamp. A GMCer replaced his alternator, and still had the dim glow
problem. He checked a diode that is supposed to eliminate this on some
production models. NO luck. He then discovered that his* 10 AMP dash
instrument gauge fuse was blown*. The fuse provides 12 volts to one side
of that lamp and if it is blown it does not have 12 volts there. When the
alternator starts putting out 15 volts there is a differential 15 - 0 and
it gets an indication. Replace the fuse (or check wiring and grounds to
make sure you have 11.5 to 12 volts at the lamp and the glow should cease,
except when the alternator is not putting out 15 volts, which is the way it
is supposed to work. It was reported in GMCMN in March 98 page 5. (John
Dolan)
from here
http://gmcmotorhome.info/engine.html#alternator
erf
On Wed, Apr 16, 2014 at 4:06 PM, gene barrow <barrowgene@gmail.com> wrote:
>
>
> David,
> It's certainly possible that I just got a defective rebuilt alternator.
>
> I can replace it again. But that won't solve my sense wire/alt light
> issue. I'd like to get it all working properly at one time.
>
> Have you removed the galley cabinet from the parts coach yet? I still
> need a GOOD one. The ones I have found so far are not as good as my
> original. It seems that the stove vent leaks and the water runs to the rear
> and settles in the back corner of those cabinets and rots the back and rear
> end panel.
>
> Thanks for the input.
> --
> Gene Barrow
> Lake Almanor, Ca.
> 1976 Palm Beach
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: Alternator/Isolator/Battery Problems/Questions [message #247658 is a reply to message #247648] |
Wed, 16 April 2014 20:15 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| Matt Colie wrote on Wed, 16 April 2014 19:09 |
| gbarrow wrote on Wed, 16 April 2014 18:21 |
Ken,
I took the readings per your instructions. At step 1 the alt was putting out over 16 volts.
I removed the alt took it to Auto Zone it failed the test on their machine. They replaced the alternator under the warranty.
New alternator also puts out 16 volts. The GOOD bulb in the alternator indicator does not light when key is turned on before starting.
Voltage at the alt wire connecting to the gauge cluster in the dash is 0 with key off 12+ with key on 14+ with engine running. So I assume the bulb not lighting is a problem with gauge cluster circuit board or contact points on light slot on the board.
Isolator readings are as anticipated from your flow chart except that the alt wire when disconnected from isolator with engine not running still reads 12+ volts.
Isolator is new- alternator is rebuilt-
How does one verify that the sense wire is functioning? How does the light failure affect the sense wire system?
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Do you mean that the heavy lead from the alternator shows ~12V when disconnected from the center terminal of the isolator with the engine off???
That just cannot happen with a good alternator.
Matt
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OK, Matt is entirely correct.
I would consider these indications two different problems. The light bulb is in the exciter circuit or start circuit for the alternator. You would like it to work correctly but it should not be part of the current over voltage problem since the alternator is starting OK.
You said you read the sense line going to the alternator and it reads about 14 volts. This a correct reading. So the question is why are you seeing over 16 volts at the center terminal of the isolator and only 14 at the sense line. These readings mean you have over a 2 volt drop (difference) between those two points. There is a .7 drop going through the isolator. That leaves an additional 1.3 or more drop unaccounted for.
First why is there +12 on the alternator lead when the lead is disconnected from the isolator? As Matt said, that needs to be found and fixed.
Second I would look at the fusible link. They are notorious for developing a resistance. The fusible link is a 6" piece of 16 gage wire between the horn relay and the big terminal labeled "Vehicle positive" (or something like that) mounted on the aluminum plate that the isolator and boost solenoid / relay are mounted on. Physically inspect this wire. Tug on it and see if it falls apart.
Third - I would get out a volt meter and meter the voltage on the engine side isolator output. I would expect it to be .7 lower that the input or about 15.3. While you are there check the House side of the isolator also. It should read about the same as the engine side. Then work forward in the circuit towards the sense line. First checking the voltage at the other side of the fusible link. If it is OK, continue checking the various wiring components working toward the sense line. You need to find that additional 1.3 voltage drop.
I am assuming that you have the engine side wiring diagram for the coach. If you do not, send me your email address and year of the coach and I'll email you one. Keep in mind that these are old coaches and many times these problems and oxidized terminal connections, oxidized fuses, and worn or oxidized switch contacts. Suspect everything in the circuit as you trace it down.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
[Updated on: Thu, 17 April 2014 06:24] Report message to a moderator |
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| Re: Alternator/Isolator/Battery Problems/Questions [message #247677 is a reply to message #247443] |
Wed, 16 April 2014 23:10 |
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WildBill
Messages: 232
Registered: January 2014
Karma: 1
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Senior Member |
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Dim glowing alternator light can be caused by a bad diode trio inside the alternator. It pulls ac off the stator and turns it into dc. Should one of t he 3 diodes in the diode trio fail your alternator light will glow. It's your power suply to the regulator. $2.00 piece at best but needs to work.
And yes in regards to the fuse, the light has 12 volts to what people would normally think the ground side of the bulb. Alternator not charging provides the ground to up illuminate bulb. Burnt out bulb, charging system won't excite, might with higher rpm's due to residual magnetism. Bulb turns out because of 12v+ on both sides of bulb when charging system working
[Updated on: Thu, 17 April 2014 11:37] Report message to a moderator |
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| Re: Alternator/Isolator/Battery Problems/Questions [message #247686 is a reply to message #247658] |
Thu, 17 April 2014 06:57 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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One other request. If you remove the center wire to the isolator that is going to the alternator again, when you read the voltage on that disconnected wire, please also read the voltage on the center terminal of the isolator. I'm expecting it to be zero.
Another shotgun thing to check. The aluminum plate that the isolator is mounted on is suppose to be grounded direct to the engine battery negative terminal. There should be a wire (about 14 gage black) running from the engine battery negative terminal direct to the aluminum plate that the isolator is mounter on. Just check to see if it is intact.
In my previous posting I said that the fusible link was attached to the fan relay. It is really attached to the HORN RELAY. I corrected that error in my post but emailers do not get corrections.
I'm looking at the wiring diagram. I should have looked at it before I previously answered your question from memory.
The sense line to the alternator is only two wires. One wire is a 12 gage red one that is connected to the horn relay on the same terminal as the fusible link. The second wire is a white 12 gage one that attaches to pin 2 of the alternator. Those two wires are attached together somewhere between those two locations. I'm not sure where that connection is.
Forget any reference I made to other connections like switches, fuses, etc. I was thinking at the time that it might have been routed through ignition switch or something. It is not. It is a simple direct route from the horn relay to the alternator pin 2 with a change of color in route.
Realizing this, I'm thinking your sense lead problem is probably the fusible link or the connection at the horn relay. I would loosen that nut on the horn relay and clean (shine) that terminal and ALL wire connectors and then reassemble. I use stainless tooth washers and anti-oxidation grease for longevity but for now just get them shiny for a good connection.
One last comment on the generator light. Mine failed a year an a half ago. Most, not all, alternators will start just fine without that circuit. Mine does so I was in no rush to fix it. I drove it that way for about a year. When I got around to fixing it, the bulb was not blown. It turned out to be a poor (oxidized) connection at the light socket. I cleaned it with a pencil eraser.
Good Luck
Ken
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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