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[GMCnet] Unknown Source of VoltGE [message #119928]

Fri, 25 March 2011 12:29

Arthur Mansfield

Messages: 290
Registered: April 2010

Karma: 0

Senior Member

ALL

I am trying to get the RV ready for the road and decided I would like to have a radio which I have not had since I bought the RV.

I just installed a new radio and speakers. While checking the input voltage I found even with the front battery disconnected I had voltage present. I also noticed with the battery disconnected and I input the key I get the buzzer for a short time and then it goes away. Is this coming from the rear battery? If so is something wrong?

Art & Doris
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Re: [GMCnet] Unknown Source of VoltGE [message #119930 is a reply to message #119928]

Fri, 25 March 2011 12:45

Bob de Kruyff

Messages: 4260
Registered: January 2004
Location: Chandler, AZ

Karma: 1

Senior Member

Arthur Mansfield wrote on Fri, 25 March 2011 11:29

It's possible a PO wired the radio to the coach battery (mine was) or you have some other component with capacitance in the circuit. After the buzzer dies down, do you still have 12V at the connection? Another possibility is that the caoch battery is connected to the chassis battery--is your boost switch off?

Bob de Kruyff
78 Eleganza
Chandler, AZ

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Re: [GMCnet] Unknown Source of VoltGE [message #119932 is a reply to message #119930]

Fri, 25 March 2011 13:39

WD0AFQ

Messages: 7111
Registered: November 2004
Location: Dexter, Mo.

Karma: 207

Senior Member

I have our cd and radio player wired to house batteries also. That is so Teri can listen while we are parked and not put a drain on the engine battery.
I suspect what Bob mentioned. You may be getting voltage from the back batteries. I did not look at the year of your coach. We have a motorcycle battery to start our Onan in the rear, 74 model. I put a combiner on it to stop the voltage from going to the house system.
Dan

3 In Stainless Exhaust Headers One Ton All Discs/Reaction Arm 355 FD/Quad Bag/Alum Radiator Manny Tran/New eng. Holley EFI/10 Tire Air Monitoring System Solarized Coach/Upgraded Windows Satelite TV/On Demand Hot Water/3Way Refer

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Re: [GMCnet] Unknown Source of VoltGE [message #119933 is a reply to message #119928]

Fri, 25 March 2011 13:39

emerystora

Messages: 4442
Registered: January 2004

Karma: 13

Senior Member

On Mar 25, 2011, at 11:29 AM, Arthur Mansfield wrote:

> ALL
>
> I am trying to get the RV ready for the road and decided I would like to have a radio which I have not had since I bought the RV.
>
> I just installed a new radio and speakers. While checking the input voltage I found even with the front battery disconnected I had voltage present. I also noticed with the battery disconnected and I input the key I get the buzzer for a short time and then it goes away. Is this coming from the rear battery? If so is something wrong?
>
> Art & Doris

Here is something that I posted back in Dec. 2004. It might be your problem:

Others have had similar problems when installing a radio. Seems that some have used a wire that went to the radio because that thought it was a ground but it actually was a wire that went from the dash lights to the radio to power the bulb in the original GMC radio. Those bulbs would receive power through the headlight switch that has a reostat to dim the dash lights. If you or your installer used that wire as a ground it would cause the problem that you have described.

If I recall it might be a gray wire. I can look this up for you on the schematic if you need me to. The problem is that if you put a test light betweeen a known 12 volt source and this wire the test bulb will light so it is easy to think that this is a ground wire when it actually isn't but it isn't hot unless the dash lights are turned on.

Most modern radios do not have the separate bulb that lights the face plate of the radio, even when the radio is off so you would just want to tape off this wire.

Emery Stora
77 Kingsley
Santa Fe, NM

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Re: [GMCnet] Unknown Source of VoltGE [message #120082 is a reply to message #119933]

Sat, 26 March 2011 22:04

Arthur Mansfield

Messages: 290
Registered: April 2010

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Senior Member

Thanks

I always disconnect the engine battery when not in use. I checked over circuits and they show power with an ohm meter but when I insert the key and the buzzer goes of the power is gone. Can I have something wrong with the house battery circuit that causes this.

Art
76 EL
On Mar 25, 2011, at 1:39 PM, Emery Stora wrote:

>
> On Mar 25, 2011, at 11:29 AM, Arthur Mansfield wrote:
>
>> ALL
>>
>> I am trying to get the RV ready for the road and decided I would like to have a radio which I have not had since I bought the RV.
>>
>> I just installed a new radio and speakers. While checking the input voltage I found even with the front battery disconnected I had voltage present. I also noticed with the battery disconnected and I input the key I get the buzzer for a short time and then it goes away. Is this coming from the rear battery? If so is something wrong?
>>
>> Art & Doris
>
> Here is something that I posted back in Dec. 2004. It might be your problem:
>
>
> Others have had similar problems when installing a radio. Seems that some have used a wire that went to the radio because that thought it was a ground but it actually was a wire that went from the dash lights to the radio to power the bulb in the original GMC radio. Those bulbs would receive power through the headlight switch that has a reostat to dim the dash lights. If you or your installer used that wire as a ground it would cause the problem that you have described.
>
> If I recall it might be a gray wire. I can look this up for you on the schematic if you need me to. The problem is that if you put a test light betweeen a known 12 volt source and this wire the test bulb will light so it is easy to think that this is a ground wire when it actually isn't but it isn't hot unless the dash lights are turned on.
>
> Most modern radios do not have the separate bulb that lights the face plate of the radio, even when the radio is off so you would just want to tape off this wire.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
>
>

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Re: [GMCnet] Unknown Source of VoltGE [message #120095 is a reply to message #120082]

Sun, 27 March 2011 08:10

Hardie Johnson

Messages: 483
Registered: January 2004
Location: Raleigh NC

Karma: 0

Senior Member

Arthur Mansfield wrote on Sat, 26 March 2011 23:04

Oddly, no one else mentioned that the old isolator my have failed. The (Yandina) combiner is a better solution.

Hardie Johnson "Crashj"
1973 26 foot Glacier, White Thing
Raleigh NC

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Re: [GMCnet] Unknown Source of VoltGE [message #120101 is a reply to message #120095]

Sun, 27 March 2011 10:45

mike miller

Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon

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Hardie Johnson wrote on Sun, 27 March 2011 06:10

...
Oddly, no one else mentioned that the old isolator my have failed. The (Yandina) combiner is a better solution.

From what I understand:

While it is POSSIBLE for the isolator to fail "shorted," (full connection -- both ways) the normal "failure mode" for the isolator is "open." (IE: no connection -- either way.)

If I had power on a "chassis" circuit with the chassis battery disconnected, I would suspect a PO added "upgrade" that crossed the house and chassis power systems before suspecting a bad part.

Art,

Do you have a combiner?

Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo' http://m000035.blogspot.com

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Re: [GMCnet] Unknown Source of VoltGE [message #120102 is a reply to message #120082]

Sun, 27 March 2011 12:14

Bob de Kruyff

Messages: 4260
Registered: January 2004
Location: Chandler, AZ

Karma: 1

Senior Member

I still think it's a capacitance issue. That's why I asked earlier if the voltage goes away once the buzzer stops. There's a component in there somewhere that has enough capacitance to show voltage until the buzzer drains it dow,

Bob de Kruyff
78 Eleganza
Chandler, AZ

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Re: [GMCnet] Unknown Source of VoltGE [message #120104 is a reply to message #120095]

Sun, 27 March 2011 12:28

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

Hardie Johnson wrote on Sun, 27 March 2011 08:10

Arthur Mansfield wrote on Sat, 26 March 2011 23:04

Oddly, no one else mentioned that the old isolator my have failed. The (Yandina) combiner is a better solution.

It would take a double diode failure inside the isolator to cause this which is highly unlikely. If you think that the isolator is your problem, simply check for voltage on the center terminal of the isolator. If you find voltage there, then disconnect the terminal going to the engine side and check the voltage on that terminal too.

I highly doubt the isolator is your problem. It is more likely something cross connected to both 12 volt electrical systems.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: [GMCnet] Unknown Source of VoltGE [message #120106 is a reply to message #120104]

Sun, 27 March 2011 12:38

James Hupy

Messages: 6806
Registered: May 2010

Karma: -62

Senior Member

There is a possibility that something like the capacitor on the refrigerator
compressor or the AC could be storing energy that is drained by the buzzer.
More likely that, than something cross or double wired. If that were the
case, the voltage would be present constantly, not just until the buzzer
drains it off. The isolator, when it fails, usually opens the circuit and no
voltage passes. Did you recently install some equipment?
Jim Hupy
Salem, OR
78 GMC Royale 403

On Sun, Mar 27, 2011 at 10:28 AM, Ken Burton <n9cv@comcast.net> wrote:

>
>
> Hardie Johnson wrote on Sun, 27 March 2011 08:10
> > Arthur Mansfield wrote on Sat, 26 March 2011 23:04
> > > Thanks
> > >
> > > I always disconnect the engine battery when not in use. I checked over
> circuits and they show power with an ohm meter but when I insert the key and
> the buzzer goes of the power is gone. Can I have something wrong with the
> house battery circuit that causes this.
> > >
> > > Art
> > > 76 EL<>
> >
> > Oddly, no one else mentioned that the old isolator my have failed. The
> (Yandina) combiner is a better solution.
>
>
> It would take a double diode failure inside the isolator to cause this
> which is highly unlikely. If you think that the isolator is your problem,
> simply check for voltage on the center terminal of the isolator. If you
> find voltage there, then disconnect the terminal going to the engine side
> and check the voltage on that terminal too.
>
> I highly doubt the isolator is your problem. It is more likely something
> cross connected to both 12 volt electrical systems.
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
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