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How To Install & Wire A 1501-L Microvac Safety Switch With 12 Volt Solenoid

Published: 11/26/2016

 

You Need A Source Of Intake Manifold Vacuum
You can get a good source of vacuum for the microvac safety switch from the plastic insulator between the carburetor and intake manifold on most small engines and generators. This is an easy part to remove from the engine and drill, tap, and insert the vacuum fitting as shown in the 3 step by step images below.

Drill a hole in the insulator or intake manifold
Step 1: Drill The Insulator With The Proper Size Bit for The 10-32 Tap

 

Use a 10-32 thread tap
Step 2: Tap The Insulator With a 10-32 Thread Tap

 

Thread the vacuum fitting into the insulator
Step 3: Thread The Vacuum Fitting Into The Insulator & Re-Install The Insulator On The Engine

 

Now Let's Take A Look At The Wiring Diagram
Next we will need to wire the microvac safety switch, the 1501-L comes with a universal bend able bracket so you can install the switch any where that is convenient on the unit. We are going to use the wiring diagram included with your switch that does not have the ignition coil in the diagram, this is for some of the older Onan Generators. The other diagram included with your switch is much easier to follow than the diagram with the coil.

Safety Switch Wiring Diagram
This Diagram Shows Where You Need To Get Your 12 volts For Each Of The Terminals

Step 1: We Need A Constant 12 volts to The IGN or Ignition Terminal
You can use 2 sources to get the 12 volts, either the large positive post on the starter, or the positive post on the battery. Some people prefer to put an on off switch in line with this wire. We need this wire to go to the post on the safety switch that is marked IGN which is short for ignition.

Step 2: We Need 12 volts From The Starter Solenoid to The STR or Starter Terminal on The Safety Switch
Using a 12 volt tester at the starter switch or the starter solenoid, be sure you have 12 volts while the engine is cranking over only, do not wire this terminal to a constant 12 volt source. With the 12 volt tester push the start button to make sure you have 12 volts while the start button is being pushed, then let go of the start switch and be sure the 12 volt tester does not show 12 volts at that point. Now we need to wire this source of 12 volts to the center post on the safety switch marked STR short for starter. What this does is gives 12 volts to the solenoid shut off while the engine is cranking over to allow the solenoid to open giving fuel to the engine to fire up as there is not enough vacuum while cranking to open that switch, there is only enough vacuum at the safety switch after the engine has started.

Step 3: Wire The 12 volt Solenoid Valve to The SOL or Solenoid Terminal on The Safety Switch
The easy part, simply wire the terminal on the safety switch marked SOL short for solenoid, wire this terminal to the 12 volt solenoid valve, the second wire on the 12 volt solenoid is for ground.

Now Let's Test The Safety Features
With the engine or generator running, pull the vacuum hose off the vacuum fitting, the engine should shut off and if it does, you have the Microvac Safety Switch and 12 volt Shut Off Solenoid wired correctly.

If you have any questions of the proper wiring of a safety shutoff switch and solenoid, call us
We Are Here To Help.

 

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