View Full Version : Magnetic start swtiches wiring?

10-03-2009, 08:02 PM
Hi all,

I'm trying to help a lucky buddy who managed to obtain two original B737 magnetic start switches, and I need a wiring diagram. I seem to remember seeing one here or on AVSIM, but I can't find it anywhere.

The switch has a total of 10 contacts, labeled X1, X2, A1/B1, A2/B2, A3/B3 and A4/B4.

A picture is attached. I assumed the X1 and X2 are 28v and control the solenoid. After failing to find a generic 28v power supply either in my closet or the local Radio Shack, I put three 9v batteries in series and attached to these contacts, but nothing happened. Am I totally off base?


10-04-2009, 02:00 AM
X1 and X2 are indeed the contacts for the solenoid. They officially need 28v but all i ever had in my hands allready worked with 12V.

At 12v the solenoid will not hold very firmly, but at 14-20V it will. So its not neccesairy to use 28V.

When powered the switch holds in the left position. Without power it jumps to the off position.

Have you fully pushed and fully turned to the left the knob with a powered solenoid?
Without a powered solenoid, you can not fully turn the switch to the left.

The other terminals are for the switch position. Inside the startswitch there's a cam that triggers a combination of microswitches.



10-04-2009, 01:06 PM
Thanks! That should solve the mystery.