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Added 6-26-22

Various Meyer E-47, E-57, E-58H, E-60 (and others) Motor Solenoids used over the years and general info.

Where to start? There is much confusion when it comes to the Motor Solenoids used on plow systems. They are very simple to understand with a little guidance. Let me start out by saying some of the names I have heard them called by. Motor Relay, contactor, silinoid (I know I spelled it wrong), solenoid, starter relay all come to mind. The manufacturer of Motor Solenoids found on most of the plows out there, calls what they make and sell DC Contactors. Ok, that's out of the way. We look at them and we name them things like 3 post, and 4 post. Well that is part of what we should be looking at. What is more important is the "Duty Cycle". That is overlooked by most for sure. The duty cycle refers to how long the actual contactors inside can be in contact ("closed"), simply put. Continous duty often have a lower rating than intermittent duty, because the intermittent duty can be higher loads for shorter periods. Until somewhat recently, intermittent duty was the standard for plows. The amp rating matters, but it is rarely listed. You ask for a part# and go home and install it.

So we know what they do, but what is the difference in them? The most common ones we see attached to snow plow hydraulic units? Not much really. NO plow manufacturer makes their own Motor Solenoids (DC Contactors, silinoids, etc..) they buy them from a vendor. Trombetta seems to have the largest presence now being used with the Douglas Dynamics brands, as well as the Bucher powered Home Plow by Meyer, as well as the Meyer Standard Operating System (SOS). Snow Dogg (Buyers) has Trombetta make quite a few different ones for them, not just for plows. So when you are stuck, and you dealer is closed, or does not have the OEM Motor Solenoid you need in stock, pick another one and off you go. In the plow world, there is what we call 3 post, and 4 post. The 4 post, the two large posts are for the battery cables (load) and the two small posts are for the trigger. It does not care if you send power or ground to trigger it, as long as the other one is connected to its respective power or ground source. Any Motor Solenoid with one side marked BAT, you MUST connect the cable from the battery to it, and the load to the other one. No markings, then it does not matter. The 3 post, in the plow world, it gets its ground through the case, that is why it must be mounted to a good ground. The single small post is for 12v+ to trigger it. This is how Meyer worked until around 2014 when they switched to a continous duty 4 post..

Old faithful, the one we have all seen. I heard it referred to as a "Ford starter solenoid" when I was a kid. Meyer used this 3 post style from the begining of their electric over hydraulic systems.

The first change in design was to allow it to also be used on the new wireless Xpress plow. First mentioned in Feb. 2005. The Xpress had a power and ground cable out to the plow, that is all, the controls were wireless. So the Motor Solenoid had to fit under a cover on the unit. Still a 3 post design.

Keep in mind this is mounted on the BACK of the unit, talk about no room to work on the vehicle. The Xpress plow came off easy enough, unless this solenoid failed.... Meyer being Meyer with their "one size fits all" mentality, this became the standard Motor Solenoid for all their plows up until around 2014. The bracket was stainless.

This is the OEM 15370 with 4 posts. IF you switch the S and I connections the plow will not work. It is also a continous duty Motor Solenoid. The case is insulated, it does not ground via the mounting bracket. This part is covered by a 5 year warranty when part of a complete new plow system, so it is not in Meyer's best interest to have to keep paying to replace them. They are well made. I only had heavy commercial plowers kill them. My personal truck has the original that is 10 years old on it.

To replace a 3 post with a 4 post, the I terminal MUST be grounded using a jumper.

This the OEM 15370 with 4 posts connected to the 22691S truck side harness. The ground goes all the way back to the battery ground terminal.

This the 15059 Diode installed on the 15370 Motor Solenoid. Rather than put the ring terminal under the mounting screws for ground, it is a more direct path back to the battery using the provided ground.

Let's look at some other Motor Solenoids. First is Meyer 05028, used on the Home Plow by Meyer auto angling. It is a Trombetta. the twist here is I connected it to a 22691S truck side harness. It can easily replace the 15370 as you can see. Note how the ground for the Motor Solenoid is in the ground lug at the battery. It is a direct ground back to the battery. Much less resistance compared to grounding via the moutning screws in the body.

Here is a Trombetta used on Western plows. Below it is the Buyers aftermarket version. SAME specs, SAME part.

Here is an aftermarket 3 post Motor Solenoid 15370 connected to a 22691S truck side harness. The ground wire is NOT NECESSARY. It grounds via the mounting screws.

Aftermarket 3 post 15370. Only 100 amps, the E-47 runs @190amps, and the E-60 runs right about 200 amps. This is why a generic stater solenoid will not last.

Aftermarket Western used in the 1970's and 80's. The old cable controlled Isarmatic unit sent GROUND to the Motor Solenoid to trigger it. To do this, a jumper is ran from battery power to the small terminal, so 12v is constant, just waiting for ground to trigger.

Let me introduce you to the Trombetta Bear DC Contactor. Look at the ratings, it can carry 225 amps continously. It is rated for 25,000 - 50,000 cycles. Note the copper contacts last half as long as silver. All the plow Motor Solenoids out there are the cheapest, copper is cheaper than silver....

Wiring schematic. I never sold one for a plow believe it or not. Every one I sold went on an electric v box spreader. Great for dual batteries, or for regulating power to a winch in the rear, or a towed vehicle or trailer.

To give you an idea of just how large the Bear is, side by side with an aftermarket 3 post 15370. The Trombetta Bear weighs over a pound more than the 15370!

I hope this info gives you a better understanding of just how Motor Solenoids work, and shows you options when you are in a tight spot. You can use every one of these Motor Solenoids on your plow without problems (other than where and how to mount). Brands don't really matter, how the Motor Solenoid is constructed (materials; eg; copper vs silver contacts) and what the load ratings are matters most. If you are stuck, get any one you can mount, and run with it until you can get the proper part. The major problem these days is the stupid covers over the pumps, and the manufcturers deciding to put the Motor Solenoid under the stupid cover on the plow itself instead of under the hood. Not that there is much room under the hood these days, but more than under the aggrivating pump cover for sure.

Visit the Trombetta web site DC Contactor section for more info than you will know what to do with.




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Suite 9
Franklin, NJ  07416
(973) 209-PLOW
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Author: Chuck Smith

Common Misspellings: Meyers, Mayer, Mayers, Myer, Myers, Maier, Maiers, Meijer.