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12V - STS-M12 24V - STS-M24
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FAA-PMA APPROVED for Certified Aircraft

Continuous Duty (Battery/Master Solenoid). Available in 12V and 24V. Activation: -(Ground) to S-Terminal. (Floating ground frame).

All stock meets Service Bulletin 72.


  • Silver Contacts provide 300A in-rush & 150A continuous-duty capability Much higher than OE units
  • Light spring and low-current coil for excellent engagement and holding capability
  • Single coil terminal (other end of coil connected to Battery terminal)


  • FAA-PMA Certified - stop using automotive parts and operating in the 'gray area' (aka. non-conformance) of the FAR's!
  • Lamar has retooled & upgraded the GOOD, "old-school" aircraft solenoids!
  • High Quality Manufacturing designed to take the beating our piston aircraft dish out
  • Upgraded to perform best with today's lightweight, high torque starters
  • Not automotive store parts with extra mystery terminals
  • Same OE terminal layout used for decades on our aircraft - simple to install
  • Silver contacts (vs. copper) for high-current capability and long-life
  • All-metal case construction
  • Customers Also Viewed
  • Frequently Purchased With


Perfect fit in my 1958 Cessna 175

Nathan J Verified Purchase


May 21, 2021

Silver contacts should give good service

James C
March 15, 2021

Performed exactly as advertised. Quality product. Outstanding service.

Dennis E
December 22, 2020

Fits & functions fine.

Ken S
October 23, 2020

A perfect replacement for the 3 post contactor on my Cessna 150.

Serloyd L
October 2, 2020

Exact fit and replacement for my old one. Works perfectly so far.

Richard C
August 17, 2020

Product came as Advertised. As always I never had any problems with the great service Aircraft Spruce provides. Thanks

Peter S
June 8, 2020

so far so good

Richard J
March 15, 2020

Good fit. Solid construction. No more jiggling battery leads to get relay to engage.

Steven A
February 19, 2020

to replace an original equipment solenoid in my OLD Mooney, this is the only game in town (and at a reasonable price too). it fit just fine and operates exactly as expected. as usual, no complaints with anything from Aircraft Spruce.

T. D
March 7, 2019


Q: What is the total current draw of the solenoid when actuated?

The total current draw is 0.8 amps.

Q: What is the difference between STec-A12 and STec-M12 relays?

The STS-M12 is for the battery master. The STS-a12 is for Auxiliary master, like a GPU.

Q: What size are the power and coil terminals? Also what is the recommended mounting orientation? I note that the 11-03161 (White-Rogers) unit recommends Cap Down orientation.

The coil terminals are #10's and the power terminals are 5/16ths. It is recommended to mount per the airframe specifications. If none, it is recommended to mount with the cap up.

Q: Does this Lamar solenoid include the diode? If not do I need it and what part number would it be?

Per Vendor: This product does not include the diode. You do not need the diode for the part to work correctly, it is simply a safety precaution some like to take. The airframe manufacturer might have a diode they recommend.

Q: What is the warranty for this unit?

12 mo from date of installation of product or 500 hrs - whichever comes first. Log books are required for warranty

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