Nasty parasitic draw from plow

[mkmc]

Hey yall
After my new plow truck (k5 blazer) killed a known good high quality battery inside of 48 hours I decided to bust out the multimeter and see if I could figure out the cause. It didn't take very long to discover what the problem was. I have a hydraulic plow, the unit under the hood has a solenoid on top with a wire straight to the positive terminal of the battery. Naturally this was my most suspect bit of kit as the interior is very barebones... upon testing that direct line I found it was drawing in excess of 1.3 AMPS even while everything else was shut off, and no draw at all otherwise.

In terms of fixing this, I was contemplating installing a kill switch for overall battery use + a bit of extra security as well, but am just curious if this is a common issue with a potentially easy fix. is it generally supposed to be wired directly to the battery but interrupted on the ground side by a switch in the cab or something to that effect (as far as I can tell all the other buttons/knobs in the cab are for other things namely: 1 lights on the plow, 2 light on the roof, and even with all those 'OFF' the draw is still present.

thanks

 

[75gmck25]

I’ve never measured voltage, but I know there are solenoids that are specifically rated for continuous duty, and some are not. For example, the common Ford external starter solenoid works fine for a starter (short engagement) , but will not last if used for something like switching a dual battery setup.

In other applications they may use latching solenoids, where it only draws power when switching. There are others that have a default “off” position, and they only move the contacts and draw power when switched to “on”. I don’t know if they have them for general use in cars, but it seems like that is what should be used for your plow.

 

[Ricko1966]

I'm sure your plow isn't supposed to have a constant draw. First thing try to find why it has a draw and fix it. An easy solution would be interrupt plow 12v power with a relay,relay trigger could be truck head lights,toggle switch,alternator etc. So plow would only have power when the truck was on so your plow couldn't drain your battery when you parked.

 

[DrvnDrvr]

Rick's right, it shouldn't have any constant draw. The solenoid probably has a short in it and needs to be replaced. My plow draws no power unless it's operating. My guess is the wire from the battery to the solenoid is a heavy gauge. There should also be smaller wire going from the solenoid to the plow control. Check and see if there is any current from the controls to the plow causing the solenoid to engage slightly.

Does yours look anything like this?

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[mkmc]

ill take a look and get some pics for you

 

[mkmc]

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[Ricko1966]

Use a test light instead of your meter. Test light in series and lit,start disconnecting components 1 at a time,watch for your light to go out.It probably is going to go out when you remove the trigger wire from the solenoid.

 

[mkmc]

Use a test light instead of your meter. Test light in series and lit,start disconnecting components 1 at a time,watch for your light to go out.It probably is going to go out when you remove the trigger wire from the solenoid.

thanks Ricko, can you confirm this here is the trigger wire? sorry i'm an electrical noob haha

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[Grit dog]

Yup it is. And it should go to the controller I believe. When you engage any plow function that solenoid latches and power to the pump motor.

 

[mkmc]

thought id close the loop on this- was sitting in the cab letting the truck warm up and happened to notice the half rubbed away sticker on top of the plow controls. it is a warning that if you leave the plow control switches anywhere but in the middle (like i had been since that's how the seller left it) that it would drain the battery lol.
did my multimeter test again with the switch in the middle and what do you know, no parasitic draw
so i was dumb but.. still glad i know how to test for this now.

im still considering installing a kill switch as an anti-theft measure. the risk is low but it feels like an easy way to prevent loss of an uninsured dream truck

 

[SDJunkMan]

thought id close the loop on this- was sitting in the cab letting the truck warm up and happened to notice the half rubbed away sticker on top of the plow controls. it is a warning that if you leave the plow control switches anywhere but in the middle (like i had been since that's how the seller left it) that it would drain the battery lol.
did my multimeter test again with the switch in the middle and what do you know, no parasitic draw
so i was dumb but.. still glad i know how to test for this now.

im still considering installing a kill switch as an anti-theft measure. the risk is low but it feels like an easy way to prevent loss of an uninsured dream truck

If it's a Meyers plow, it can also burn out the selonoid if left in the down position (I've mistakenly burned out several over the years). The plow uses power to open the valve and closes it when power is removed. It really sucks to have the selonoid go out in the down position when you are away from home, I've had to drop my plow in the corner of one of my lots and chase down a selonoid so I could finish plowing, now I usually carry a spare.

 

[DrvnDrvr]

On my plow the switches are momentary so never had these issues.

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