jmiller
Recruit
This was a thread in the 6.5 forum where I suggested a test but did not have any actual results to share.
The test consists of using a test light to check for excessive current draw that could cause the batteries to drain down over night.
This test would works on any vehicle, with or without a computer or fancy electronic memory radio's.
Disconnect the battery Ground Cable(s)
Remove the under hood lamp
disable or assure the dome light is off
Connect a test lamp to the negative battery terminal and Ground.
On a non computer vehicle, the lamp should be dark, turning on any accessory should cause a bright lamp.
On a computer controlled vehicle, the lamp should glow dimly.
On my 98 6.5 work truck I preformed the test with the following results:
A volt meter was added across the test light to show the dimness of the lamp for each step.
With Head light switch in the "ON" Position - Full brightness and full 12v across the test lamp
Everything "OFF" all fuses installed - Slightly dimmed lamp, 7v across the lamp, noticed a buzzing sound from a relay that can not engage.
After removing the CTSY Fuse to stop buzzing relay. Very dim lamp with less than 3v across the lamp
I did not chase every fuse for items that draw the small current seen in the last picture.
On my truck, the radio bat fuse, security fuse and ECM fuse should get the test light to go out. But the point of the test is that if a slightly dimmed lamp dropping 7 volts can set for weeks and start just fine then you could consider this to be normal. If you see a fully bright lamp and +11.5 volts, something is on that should not be. You can start pulling fuses until the lamp dims.
This goes to show a simple tool will do the job, an expensive current clamp or ampmeter is not required.
The principal is voltage = current X resistance. (Ohm's Law)
The test light lamp has a resistance of some constant value.
The vehicle has a resistance of some value that varies based on what is turned on. (variable resistance)
Higher the resistance, lower the current if the voltage is constant (@12.6v)
Adding the test lamp in series with the vehicle splits the load. (creates a voltage divider)
Since the lamp will draw a certain current at full brightness, any resistance added in the series will reduce the current and dim the lamp.
Lower the voltage across the lamp, the less current in the circuit.
I hope someone find this useful.
The test consists of using a test light to check for excessive current draw that could cause the batteries to drain down over night.
This test would works on any vehicle, with or without a computer or fancy electronic memory radio's.
Disconnect the battery Ground Cable(s)
Remove the under hood lamp
disable or assure the dome light is off
Connect a test lamp to the negative battery terminal and Ground.
On a non computer vehicle, the lamp should be dark, turning on any accessory should cause a bright lamp.
On a computer controlled vehicle, the lamp should glow dimly.
On my 98 6.5 work truck I preformed the test with the following results:
A volt meter was added across the test light to show the dimness of the lamp for each step.
With Head light switch in the "ON" Position - Full brightness and full 12v across the test lamp
Everything "OFF" all fuses installed - Slightly dimmed lamp, 7v across the lamp, noticed a buzzing sound from a relay that can not engage.
After removing the CTSY Fuse to stop buzzing relay. Very dim lamp with less than 3v across the lamp
I did not chase every fuse for items that draw the small current seen in the last picture.
On my truck, the radio bat fuse, security fuse and ECM fuse should get the test light to go out. But the point of the test is that if a slightly dimmed lamp dropping 7 volts can set for weeks and start just fine then you could consider this to be normal. If you see a fully bright lamp and +11.5 volts, something is on that should not be. You can start pulling fuses until the lamp dims.
This goes to show a simple tool will do the job, an expensive current clamp or ampmeter is not required.
The principal is voltage = current X resistance. (Ohm's Law)
The test light lamp has a resistance of some constant value.
The vehicle has a resistance of some value that varies based on what is turned on. (variable resistance)
Higher the resistance, lower the current if the voltage is constant (@12.6v)
Adding the test lamp in series with the vehicle splits the load. (creates a voltage divider)
Since the lamp will draw a certain current at full brightness, any resistance added in the series will reduce the current and dim the lamp.
Lower the voltage across the lamp, the less current in the circuit.
I hope someone find this useful.
