Home » Public Forums » GMCnet » Electrical issue (12V mystery draw)
| Electrical issue [message #266067] |
Fri, 14 November 2014 12:26  |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
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Been having engine battery/ alt problems.
Installed new/rebuilt alt 2 weeks ago.
Disconnected and cleaned all pos+ cable connections except batt cable on starter.
Installed new neg- cable between batt and engine block.
Installed new battery this a.m.
With pos cable connected (ignition switch off) and neg cable disconnected from batt; multimeter between battery and neg cable reads 12V. Doesn't seem right to me. If I leave the cables connected I assume I'll wind up with a dead battery.
Please tell me I am wrong.
The radio is turned off (only the memory light is on) nothing else that is powered by the engine batt is on.
Other than removing fuses how do I look for the source of the load.
Thanks for input.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: [GMCnet] Electrical issue [message #266072 is a reply to message #266069] |
Fri, 14 November 2014 13:14  |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
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Hi Jim,
Boost is spring loaded and is NOT on. What next? Thanks for being there and responding. With the weather up there I guess you're house/shop bound.
My wife borrowed your can opener from Judy at Treasure Island and you left before we returned it. I'll send you the price of a new Swing-A-Way. The only one worth owning. I also have a Route 66 book from Dwayne I need to get returned.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: Electrical issue [message #266081 is a reply to message #266067] |
Fri, 14 November 2014 15:22 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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What meter are you using? Most digital meters have a screaming high input impedance, which means a few microamps of current flow will be sufficient for the meter to read the battery voltage. For a proper test, set the meter to read current, and see what the current flow actually is. If it's a few milliamps, I wouldn't worry over it. More than that, unfuse and disconnect until it goes away, and then look at whatever made it go away. Radio memory, clocks, the icebox in some instances, etc.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
[Updated on: Fri, 14 November 2014 15:22] Report message to a moderator |
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| Re: [GMCnet] Electrical issue [message #266082 is a reply to message #266072] |
Fri, 14 November 2014 15:49 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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gbarrow wrote on Fri, 14 November 2014 13:26Been having engine battery/ alt problems.
Installed new/rebuilt alt 2 weeks ago.
Disconnected and cleaned all pos+ cable connections except batt cable on starter.
Installed new neg- cable between batt and engine block.
Installed new battery this a.m.
With pos cable connected (ignition switch off) and neg cable disconnected from batt; multimeter between battery and neg cable reads 12V. Doesn't seem right to me. If I leave the cables connected I assume I'll wind up with a dead battery.
Please tell me I am wrong.
The radio is turned off (only the memory light is on) nothing else that is powered by the engine batt is on.
Other than removing fuses how do I look for the source of the load.
Thanks for input.
gbarrow wrote on Fri, 14 November 2014 14:14Hi Jim,
Boost is spring loaded and is NOT on. What next? Thanks for being there and responding.
Snipped can openers and books
Gene,
The voltmeter will read ~12V with little or no provocation. It is just not the best test here.
Even the radio memory can make that happen.
Does the meter have any current scale?
If yes, start with the highest. Keep bring the scale down until you get some value that is stable and makes sense.
If it does not get real close to zero, tell us what you get.
If you can't make that work. Take a little tiny (smaller is better here) 12v light bulb and solder two wires with alligator clips and put it between the battery and everything else.
Does it light??
If yes, Sorry, the only way other than getting an expensive clamp on DC current probe is to start pulling fuses.
If you put the light where you can see it, this can go pretty fast. If you get to the end of the fuses and the light is still on.... Now you need to hunt up what the PO added. Look for inline fuses near major battery connections.
If no, we need a better instrument.
Tell us what happens.
We can walk you through this. I have done it by marine VHF more than once. <over>
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| [GMCnet] Electrical issue [message #266105 is a reply to message #266082] |
Sat, 15 November 2014 06:36 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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You miss the point here ( need to read:). We are not measuring volts here ,
we are id-ing sources, and drains.. (3.5 digit meter will show current
drains)
Use kens flow chart to see
-is there a combiner
-which batt system has the load
-are changing systems working
-what is the load like?
-you have to know where to look!!!
When you get close , use bovees sounders
http://www.gmcmhphotos.com/photos/tvs-and-vacuum/p3340.html
Looking at currents , is last resort
Erf
On Friday, November 14, 2014, Matt Colie wrote:
> gbarrow wrote on Fri, 14 November 2014 13:26
>> Been having engine battery/ alt problems.
>> Installed new/rebuilt alt 2 weeks ago.
>> Disconnected and cleaned all pos+ cable connections except batt cable on
> starter.
>> Installed new neg- cable between batt and engine block.
>>
>> Installed new battery this a.m.
>>
>> With pos cable connected (ignition switch off) and neg cable
> disconnected from batt; multimeter between battery and neg cable reads 12V.
> Doesn't
>> seem right to me. If I leave the cables connected I assume I'll wind up
> with a dead battery.
>> Please tell me I am wrong.
>>
>> The radio is turned off (only the memory light is on) nothing else that
> is powered by the engine batt is on.
>>
>> Other than removing fuses how do I look for the source of the load.
>>
>> Thanks for input.
>
> gbarrow wrote on Fri, 14 November 2014 14:14
>> Hi Jim,
>> Boost is spring loaded and is NOT on. What next? Thanks for being there
> and responding.
>> Snipped can openers and books
>
> Gene,
>
> The voltmeter will read ~12V with little or no provocation. It is just
> not the best test here.
> Even the radio memory can make that happen.
>
> Does the meter have any current scale?
> If yes, start with the highest. Keep bring the scale down until you get
> some value that is stable and makes sense.
> If it does not get real close to zero, tell us what you get.
> If you can't make that work. Take a little tiny (smaller is better here)
> 12v light bulb and solder two wires with alligator clips and put it between
> the battery and everything else.
> Does it light??
> If yes, Sorry, the only way other than getting an expensive clamp on DC
> current probe is to start pulling fuses.
> If you put the light where you can see it, this can go pretty fast. If
> you get to the end of the fuses and the light is still on.... Now you need
> to
> hunt up what the PO added. Look for inline fuses near major battery
> connections.
> If no, we need a better instrument.
>
> Tell us what happens.
> We can walk you through this. I have done it by marine VHF more than
> once.
>
> Matt
> --
> Matt & Mary Colie - Members GMCMI, GMCES
> '73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
> SE Michigan - Twixt A2 and Detroit
> _______________________________________________
> 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: Electrical issue [message #266109 is a reply to message #266081] |
Sat, 15 November 2014 07:41 |
gbarrow2
Messages: 765
Registered: February 2004
Location: Lake Almanor, Ca./ Red Bl...
Karma: 3
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Senior Member |
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Thanks to all for suggestions;
Johnny Bridges gets the prize? Reading the voltage with my super expensive Harbor Freight multi meter was only half the story.
If I set the meter right and read it correctly the current draw was 13 milliamps. Not enough to be a problem.
Public schools should teach more details about electricity than Ben Franklin with his kite and key.
Gene Barrow
Lake Almanor, Ca.
1976 Palm Beach
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| Re: [GMCnet] Electrical issue [message #266115 is a reply to message #266109] |
Sat, 15 November 2014 10:43 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I remember my first encounter with a Techtronics Oscilloscope. Small 4"
round CRT display with lines etched into the glass. At least 4 gillion
knobs on the front. You think a DMM has a lot of scales? Try that old Tec
Scope. Then came Dwell Meters, Allen Smart Scopes, Sun was the biggest
producer of Automotive Diagnostic Centers. Old Sun distributor machines,
similar to the type that Dick Paterson uses to recurve the Springfield
ignitions for our GMC's, and then came OBD 1, And OBD 2 & 2a. I almost
forgot GM CCC. Push the Fan and Warmer buttons at the same time, and the
lights in the heater/cooling module would flash a special sequence to
reveal the "magic sequence" that would tell you in a flash of light just
what was wrong with your GM car. Yeah, Right! Same ECM in the 747 computer
that Howell uses in the GMC Fuel injection. Transient current drains, you
say. Just wait. You ain't seen nuthin' yet.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Sat, Nov 15, 2014 at 5:41 AM, gene barrow wrote:
> Thanks to all for suggestions;
> Johnny Bridges gets the prize? Reading the voltage with my super expensive
> Harbor Freight multi meter was only half the story.
> If I set the meter right and read it correctly the current draw was 13
> milliamps. Not enough to be a problem.
>
> Public schools should teach more details about electricity than Ben
> Franklin with his kite and key.
>
> --
> 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
>
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Unsubscribe or Change List Options:
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| Re: [GMCnet] Electrical issue [message #266116 is a reply to message #266105] |
Sat, 15 November 2014 11:58 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Mr ERFisher wrote on Sat, 15 November 2014 07:36You miss the point here ( need to read:). We are not measuring volts here ,
we are id-ing sources, and drains.. (3.5 digit meter will show current drains)
Use kens flow chart to see
-is there a combiner
-which batt system has the load
-are changing systems working
-what is the load like?
-you have to know where to look!!!
When you get close , use bovees sounders
http://www.gmcmhphotos.com/photos/tvs-and-vacuum/p3340.html
Looking at currents , is last resort
Erf
Gene,
He has found that he has a 13mil (0.013 ampere) drain.
So, if he has a decent 80AH battery he should be good for about 3 months (give or take).
If I were he, I might go looking for that 13mils just to know what it is.
It is a complete mystery to me why you think looking for current when there is a current drain is a last resort.
We are also trying to do a remote diagnostic with a man that has limited experience and an unknown instrument.
When I had the marine (pleasure boat) service, I kept a record of what meter each owner carried. If he didn't have one, I would give him one and tell him to leave it in the package until he got in touch with me.
A current probe is a nice thing to have. You can measure the current flow in any circuit you can get it around without disconnecting anything. Unfortunately, the good ones aren't cheap. Mine it cost 300$ but it will read from 400A to 20mil barefoot. If you don't have one, once you establish that there really is a drain on the bank, the remaining resort is pulling circuits (be they fuses or breakers). This is much faster with a light bulb in series. When the light goes out, you found it.... Like when the oven light in the coach got left one.
I fail to see how a vacuum diagram is germane to this topic.
Matt -
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Electrical issue [message #266119 is a reply to message #266116] |
Sat, 15 November 2014 12:35 |
Otterwan
Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...
Karma: 0
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Senior Member |
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The battery in my son's car would randomly go dead (like down to 5 volts) if he didn't drive it for a week or two. But some times it would go two or three weeks and start fine. Battery would charge and hold charge fine if not connected. Finally tracked the draw to an FM iPod transmitter the he occasionally left plugged into the cigarette lighter socket.
Moral here is anything in the cigarette lighter socket is a draw.
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: [GMCnet] Electrical issue [message #266120 is a reply to message #266115] |
Sat, 15 November 2014 12:40 |
lotsofspareparts
Messages: 726
Registered: May 2014
Location: Arlington, WA
Karma: -9
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Senior Member |
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James Hupy wrote on Sat, 15 November 2014 08:43I remember my first encounter with a Techtronics Oscilloscope. Small 4"
round CRT display with lines etched into the glass. At least 4 gillion
knobs on the front. You think a DMM has a lot of scales? Try that old Tec
Scope. Then came Dwell Meters, Allen Smart Scopes, Sun was the biggest
producer of Automotive Diagnostic Centers. Old Sun distributor machines,
similar to the type that Dick Paterson uses to recurve the Springfield
ignitions for our GMC's, and then came OBD 1, And OBD 2 & 2a. I almost
forgot GM CCC. Push the Fan and Warmer buttons at the same time, and the
lights in the heater/cooling module would flash a special sequence to
reveal the "magic sequence" that would tell you in a flash of light just
what was wrong with your GM car. Yeah, Right! Same ECM in the 747 computer
that Howell uses in the GMC Fuel injection. Transient current drains, you
say. Just wait. You ain't seen nuthin' yet.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Sat, Nov 15, 2014 at 5:41 AM, gene barrow wrote:
> Thanks to all for suggestions;
> Johnny Bridges gets the prize? Reading the voltage with my super expensive
> Harbor Freight multi meter was only half the story.
> If I set the meter right and read it correctly the current draw was 13
> milliamps. Not enough to be a problem.
>
> Public schools should teach more details about electricity than Ben
> Franklin with his kite and key.
>
> --
> 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
>
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
I have one of those Tek Scopes, mine is a type 549 Storage Oscilloscope. It has a type CA Plug in. Vintage 1960. Still works too, and has about 200 tubes in it.
Jared
Jared & Tina Lazaron + 14yr old Daughter.....
77 Eleganza II "Recherché".....
73 Canyon Lands 230 "Elephant"
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| Re: Electrical issue [message #266125 is a reply to message #266067] |
Sat, 15 November 2014 13:12 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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We've a saying in my business regarding oscilloscopes and swept analyzers ( specialized type of 'scope for the non-electronic weenie types), "There's Tek, and there's everybody else." I currently have an Advantest analyzer and an Agilent analyzer, and the saying still holds. I borrow an old 396P when I want to see what the RF system is actually doing.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Electrical issue [message #266128 is a reply to message #266069] |
Sat, 15 November 2014 13:24 |
<rallymaster
Messages: 361
Registered: May 2014
Karma: 2
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Senior Member |
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"You betchum, Red Ryder"
Even after Danaher acquired them.
I remember (vaguely) talking to someone who worked somewhere in Salem
(?), OR, a buncha years ago. The subject got around to test equipment,
and to scopes. The guy said that HP was the best, and they had two of
them in a storage closet, but everybody used the TEK 545, cause no one
could get the HPs to work.
RonC
On Sat, 15 Nov 2014 12:12:55 -0700 Johnny Bridges
writes:
> We've a saying in my business regarding oscilloscopes and swept
> analyzers ( specialized type of 'scope for the non-electronic weenie
> types), "There's
> Tek, and there's everybody else." I currently have an Advantest
> analyzer and an Agilent analyzer, and the saying still holds. I
> borrow an old 396P
> when I want to see what the RF system is actually doing.
>
> --johnny
>
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| Re: [GMCnet] Electrical issue [message #266131 is a reply to message #266128] |
Sat, 15 November 2014 14:09 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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Blame that name change on my Samsung cell phone spell correction software.
I know it is Tek. Phone refuses to accept that spelling. Golly, I love
hand held devices smarter than I am supposed to be. (Grin)
Jim Hupy
On Nov 15, 2014 11:26 AM, wrote:
> "You betchum, Red Ryder"
>
> Even after Danaher acquired them.
> I remember (vaguely) talking to someone who worked somewhere in Salem
> (?), OR, a buncha years ago. The subject got around to test equipment,
> and to scopes. The guy said that HP was the best, and they had two of
> them in a storage closet, but everybody used the TEK 545, cause no one
> could get the HPs to work.
>
> RonC
>
> On Sat, 15 Nov 2014 12:12:55 -0700 Johnny Bridges
> writes:
>> We've a saying in my business regarding oscilloscopes and swept
>> analyzers ( specialized type of 'scope for the non-electronic weenie
>> types), "There's
>> Tek, and there's everybody else." I currently have an Advantest
>> analyzer and an Agilent analyzer, and the saying still holds. I
>> borrow an old 396P
>> when I want to see what the RF system is actually doing.
>>
>> --johnny
>>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: Electrical issue [message #266139 is a reply to message #266067] |
Sat, 15 November 2014 18:13 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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I use to carry a Tektronics scope in my trunk for work. I believe it is a 475. I used it quite frequently for work things. It was and still is bullet proof. Every two years we sent them in for calibration but they never were off. I drove a convertible and one time the top leaked in the winter and soaked the trunk. I got it out at a customer site and it was full of ice. I brought it inside and opened the front gates the IBM CPU and stuck the scope inside it to warm it up. 1/2 hour later it was thawed and dry. It worked just fine. I still have that scope today and I used it a couple of weeks ago to look at the ignition on a Chevy Blazer. It makes it very easy to spot an open spark plug wire, bad plug, or almost anything bad on the high voltage side of the ignition system.
I wish I could use it on an GMC HEI system but I can not figure out how to probe the high voltage output from the coil to the rotor. What I always have done in the past was to display the coil output on channel 1 and trigger the sweep off of on the #1 plug wire.
I also have used it to spot bad diodes in the alternator without having to remove it from the car.
The modern coil on plug systems put an end to that method of ignition diagnosis.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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