How to create a parasitic drain?

gijoe985 · Post by **gijoe985** » Tue Feb 21, 2012 9:33 am

Hey all,

Joe the shop teacher here. I want to do a lesson with my students on how to test for a parasitic drain. What do you think the easiest way to create one would be? Obviously I could just leave a dome light on or something, but I want it to be hidden so that my students will actually have to use a DVOM and pull fuses? Any suggestions?

I guess I just need to find a lower amp circuit and ground a wire. That should keep them hunting for a while.

BCLS776 · Post by **BCLS776** » Tue Feb 21, 2012 10:05 am

How about you paint the light bulb black or cover it with tape? That'll make it tougher to find.

gijoe985 · Post by **gijoe985** » Tue Feb 21, 2012 10:17 am

BCLS776 wrote:How about you paint the light bulb black or cover it with tape? That'll make it tougher to find.

I've thought about that. It would work, but would be less like a real life situation where a wire gets pinched...

I just don't want to short something with too much amps. I don't need a fire.

crazyman · Post by **crazyman** » Tue Feb 21, 2012 6:53 pm

Hide a relay and power up the 85 and 86 terminals.

gijoe985 · Post by **gijoe985** » Thu Feb 23, 2012 3:13 pm

crazyman wrote:Hide a relay and power up the 85 and 86 terminals.

What would I wire it into? Just into any circuit?

crazyman · Post by **crazyman** » Thu Feb 23, 2012 8:44 pm

Whatever you wanted to wire it to that has power with the key off. It won't be much of a draw, but it will still be a draw. Just put a switch in the circuit so you can turn it off when not in use during class.

Post by **Kevin Johnson** » Thu Feb 23, 2012 11:57 pm

This brings back a good memory of talking with Clyde Davidson. He was a pyrometer and furnace tech at River Rouge starting back in the 1920s. He talked about having to find a drain that his teacher had cleverly concealed as part of a test. No, I don't recall exactly what was done.

Other memory of Clyde: He painted his room completely black so he could get to sleep quickly when he was a student.

af2 · Post by **af2** » Fri Feb 24, 2012 4:34 pm

gijoe985 wrote:Hey all,

Joe the shop teacher here. I want to do a lesson with my students on how to test for a parasitic drain. What do you think the easiest way to create one would be? Obviously I could just leave a dome light on or something, but I want it to be hidden so that my students will actually have to use a DVOM and pull fuses? Any suggestions?

A resistor between a 5 or smaller amp to earth behind the fuse block will work. You can try different values for more or less drain.

underhead valve · Post by **underhead valve** » Sun Feb 26, 2012 10:48 am

If the car you want for the test is a "network" car you only need to prevent the network from going to sleep, this will make for a very interesting search, --the componet creating the draw many times doesn't have a draw, but it keeps the network from sleeping so all the other componets have a slight draw from not sleeping ---a 2004 c240 benz with a bad seat computer would make for interesting testing.

Perhaps calling the dealers for the cars you have avalible, ask what causes draws---perhaps you can even get some defective parts to install ---this will make for a more "real world" experience than just hiding a resistor

Possibly taking out the domelight bulb and adjusting the door contact to think open door so the electronics draw but no light.

Cogburn · Post by **Cogburn** » Sat Mar 03, 2012 9:26 am

A 33Ω resistor across the radio plug or some other component will make them look for a while and actually simulate a shorted component.

peejay · Post by **peejay** » Tue Mar 06, 2012 8:53 am

Cogburn wrote:A 33Ω resistor across the radio plug or some other component will make them look for a while and actually simulate a shorted component.

That's what i am thinking... something with relatively high resistance, backprobed across the power and ground leads of the component you want to make faulty.

Mmfh · Post by **Mmfh** » Sat Mar 10, 2012 10:27 am

Could you lock up the blower motor, put something in it so it doesn't turn. Then turn the heater on low. Might take a little bit to find that and can be staged like a real life situation.

AMorrison · Post by **AMorrison** » Sat May 12, 2012 12:16 am

You could always marry my ex wife.

Hairyscreech · Post by **Hairyscreech** » Thu Jun 07, 2012 10:49 pm

If its a saloon with a trunk light then rigging the micro switch that lights the light is a good one, it will keep the light on even when the boot is shut, thus it takes a while to find as you only spot it being on all the time if you can see into the trunk when its shut.
Same deal with a glove box light, its supposed to be on when the glove box is open so no one will suspect a fault unless they can see its still on when the glove box is shut.
Both of these are pretty common faults in the real world.

Rig the fuel pump relay to run the fuel pump all the time? However i guess that will only work if the pump is really quiet or where they are doing it is noisy.

Workshop · Post by **Workshop** » Sat Jun 09, 2012 9:11 pm

AMorrison wrote:You could always marry my ex wife.

Ha, Ha..... Oh Yeah!...

Don Terrill’s Speed-Talk

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