HK40USP
Santee,CA
Full Member
Joined: 07/28/2002
View Profile
|
Tom_Anderson wrote:HK40USP wrote:Tom_Anderson wrote:Do you mean .83 amps? How are you measuring it?
tom...I have a multi-meter set on 20vdc...measure is across the knife switch on the neg post.....Jim
Set the meter for 10A instead of volts and measure it again. That will give you a much more meaningful reading. Any significant draw should give you a reading of full battery voltage (12.6V) when you measure voltage drop (how you're doing it now).
thanks, I will try that tomorrow....
1996 Gulfstream Sunvoyager, 34 ft, no/slides
Spartan Chassis, B5.9 230 hp Cummins
|
Harvard
51.37N 114.42W
Senior Member
Joined: 12/24/2005
View Profile
|
If the switch were open AND if there were a significant load (current path) the voltage would be about 12.6 VDC (battery voltage) across the meter. Because you are only measuring 0.83 Volts then it means the internal resistance of the meter is much less (12.6 / 0.83 = 15 times less) then the resistance path of the vehicle. Translation: The resistance path of the vehicle is probably 10 MegOhm * 15 or 150 MegOhms. Better go find something more useful to do with your meter! Just kidding! 
Edited for spelling....and, in other words the current draw is about 12.6V/160,000,000Ohms = 0.000000078 Amps. Your battery should last til the next ice age....
* This post was
last
edited 08/18/08 08:41am by Harvard *
View edit history
|
Harvard
51.37N 114.42W
Senior Member
Joined: 12/24/2005
View Profile
|
Capt. Flipper wrote:If you are getting .83 volts across the open knife switch, you don't have a problem. VOM's are typically 20,000 ohms of internal resistance per volt and that translates into a very small parasitic current draw.
Not to be picky, but, 20,000 Ohms per Volt (in theory, 20 x 20,000 = 400,000 Ohms on a 20 volt range) applies to the "pre solid state" mechanical meter movements where the energy to move the meter came from the circuit under test. With a modern DVM that uses a 9 Volt battery to power the meter, the input resistance is typically 10 MegOhms regardless of the voltage range selected.
|
HK40USP
Santee,CA
Full Member
Joined: 07/28/2002
View Profile
|
HK40USP wrote:Tom_Anderson wrote:HK40USP wrote:Tom_Anderson wrote:Do you mean .83 amps? How are you measuring it?
tom...I have a multi-meter set on 20vdc...measure is across the knife switch on the neg post.....Jim
Set the meter for 10A instead of volts and measure it again. That will give you a much more meaningful reading. Any significant draw should give you a reading of full battery voltage (12.6V) when you measure voltage drop (how you're doing it now).
thanks, I will try that tomorrow....
Tom... the amp measure was 3.51
|
Harvard
51.37N 114.42W
Senior Member
Joined: 12/24/2005
View Profile
|
Are you sure, 3.51 Amps would kill your chassis battery within 24 hours....the 0.83 volts and 3.51 amps do not equate to one another if you are measuring across the open knife switch with the ignition OFF. It just does not add up....maybe 3.51 milliAmps but that still does not fit the 0.83 volts.
|
|
|
mike4947
N. Syracuse, NY
Moderator
Joined: 08/26/2002
View Profile
 Online
|
Jim, I hate to say it but the last time we saw measurements like that we pulled our hair out until us geniuses replaced the battery in the multimeter.
blog.rv.net Your daily guide to the Open Road
Subscribe to the daily digest
Want to sell some of your gear? -
Free Classified Listings on RV.Net
They say you learn by your mistakes, in that case I must be a genius.
|
HK40USP
Santee,CA
Full Member
Joined: 07/28/2002
View Profile
|
Harvard wrote:Are you sure, 3.51 Amps would kill your chassis battery within 24 hours....the 0.83 volts and 3.51 amps do not equate to one another if you are measuring across the open knife switch with the ignition OFF. It just does not add up....maybe 3.51 milliAmps but that still does not fit the 0.83 volts.
I had the "electro tek" meter set on 10 amp setting and yes it drains the batteries in about 1 to 2 days,....if the engine is not running I open the switch.....????????????????????????
does this sound like a direct short? there is no sparking when I close the switch.......
|
HK40USP
Santee,CA
Full Member
Joined: 07/28/2002
View Profile
|
mike4947 wrote:Jim, I hate to say it but the last time we saw measurements like that we pulled our hair out until us geniuses replaced the battery in the multimeter.
LOL... i wish that was the solution....new 9volt installed
|
50pascals
rochester, ny
Senior Member
Joined: 01/10/2008
View Profile
|
time to start pulling fuses and following wires until you find it.
Go to the fuse box for the chassis and measure all the circuits for draw. Or pull fuses one at a time while watching the meter.
Then do the same thing for the house fuse panel.
BTW 3.5 amps is low enough that you could rig up an extension cord, or lamp cord from the knife switch to get the meter near the fuse panel if you have to do this yourself.
I'm assuming your meter is inserted in the circuit to measure amp draw. Mine is a clamp type that will measure current once clamped around the wire. Much easier to do yourself.
|
zmotorsports
Utah
Senior Member
Joined: 11/29/2007
View Profile
 Offline
|
HK40USP wrote:HK40USP wrote:Tom_Anderson wrote:HK40USP wrote:Tom_Anderson wrote:Do you mean .83 amps? How are you measuring it?
tom...I have a multi-meter set on 20vdc...measure is across the knife switch on the neg post.....Jim
Set the meter for 10A instead of volts and measure it again. That will give you a much more meaningful reading. Any significant draw should give you a reading of full battery voltage (12.6V) when you measure voltage drop (how you're doing it now).
thanks, I will try that tomorrow....
Tom... the amp measure was 3.51
Make sure when measuring amps that you put the meter in 'series' with the circuit. You cannot read amps across a circuit like you do with volts. Also, with the switch open you should see battery volts. If you are seeing .83 volts with the switch closed then there is a problem, it would say that you had less than one volt (.83VDC) voltage drop across the switch. This would suggest that the contacts or connections on the switch were bad. I personally don't like anything over .2VDC voltage drop across any switch or connection. Mike.
Mike & Chrystal (F315002)
2003 Monaco Dynasty/ 26' Haulmark Edge trailer
1996 Jeep Grand Cherokee toad
|
|
|
