How to create a parasitic drain?

Tech questions that don't fit above forums

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MotionMachine
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Re: How to create a parasitic drain?

Post by MotionMachine » Mon Jun 25, 2012 9:30 am

AMorrison wrote:You could always marry my ex wife.
....or keep re-electing progressive socialists

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Re: How to create a parasitic drain?

Post by pheyden » Sun Dec 16, 2012 11:20 pm

Here's one for you. A bit off-topic but still a good one. Had a customer years ago that had a tow truck business. He had 2-way radios in the truck (big 100 watt GE). He came in one day and said that for some reason every time he took his big diesel wrecker up on the freeway, the 2-way radio would stop working. Yet, whenever he would arrive at my shop the radio worked fine. Yes, I went with him and sure enough as soon as he got up on the freeway and up to speed, no more 2-way radio. Anyone want to guess what caused this?

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Re: How to create a parasitic drain?

Post by Kevin Johnson » Mon Dec 17, 2012 12:16 am

pheyden wrote:Here's one for you. A bit off-topic but still a good one. Had a customer years ago that had a tow truck business. He had 2-way radios in the truck (big 100 watt GE). He came in one day and said that for some reason every time he took his big diesel wrecker up on the freeway, the 2-way radio would stop working. Yet, whenever he would arrive at my shop the radio worked fine. Yes, I went with him and sure enough as soon as he got up on the freeway and up to speed, no more 2-way radio. Anyone want to guess what caused this?

Wild guess. The force of the air caused his whip antenna to go horizontal and changed it from omnidirectional to more of a directional -- if it was mounted on the back of the cab that surface might have acted as a vertical ground plane.

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Re: How to create a parasitic drain?

Post by pheyden » Mon Dec 17, 2012 11:18 pm

Actually, some bright installer, when looking for a good 12V power source (remember a 100 watt transmitter will draw many amps) found a huge power wire on the back wall of the cab. It turned out that it was part of a switching circuit for the 2 speed rear end. Ergo - When he was up on the freeway at cruising speeds, he was in high range, thus no radio. Took a bit to find that one.

Paul

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Re: How to create a parasitic drain?

Post by Kevin Johnson » Tue Dec 18, 2012 7:22 am

pheyden wrote:Actually, some bright installer, when looking for a good 12V power source (remember a 100 watt transmitter will draw many amps) found a huge power wire on the back wall of the cab. It turned out that it was part of a switching circuit for the 2 speed rear end. Ergo - When he was up on the freeway at cruising speeds, he was in high range, thus no radio. Took a bit to find that one.

Paul

Interesting -- it would have cut off his radio like a switch then. I took it that the radio was still on but would not "work" as in receiving signals.

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Re: How to create a parasitic drain?

Post by user-3597028 » Tue Dec 18, 2012 8:58 am

An electric choke pull off will do the trick.

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Re: How to create a parasitic drain?

Post by MadBill » Wed Jan 02, 2013 9:55 pm

Hairyscreech wrote: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.
I had this one for real on my '70 Z-28. After I re-arched the rear springs the battery started going flat. The added rear height was just enough to tilt the mercury switch.. #-o
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.

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