Technical Wiring issue

It says to run the wire to the ignition switch. Which terminal on the ignition switch do I use


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What do you want it to do if you get low oil pressure? Horn, kill the engine etc.

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if you are using that switch for an electric fuel pump, you want to run the wire to the terminal that gets power when the engine is running. might need to do a volt or continuity test to tell which one it is.

 

Connect the I terminal to the terminal on the ignition switch that has power when the key is in the ON position. The S terminal should go to the terminal on the solenoid that receives power from the ignition switch when cranking the engine over. The P terminal goes to the pump.

 

If you are using the switch for electric fuel pump ....should be using a relay... most of these switchs really cant carry the current that the electric pumps draw...top pic shows connected through relay....could save a break down because of switch failed through current overload...
I use a different type of switch which operates from the coil pulse (tacho pin).... pulse from coil opens switch..no pulse switches off....also it opens for 5 seconds when first switched on.. which will operate fuel pump to prime carby....This switch is a safety switch used for LPG installations for cars

 

Electric fuel pumps have varying current requirements, some are really low current, others are high current. A relay is a good idea, but might not be needed. I don't have one on mine, I've been using that PS64 switch on several different vehicles over the years, although always with the same 6-71 blower. I think one time the switch died electrically, a few other times it started leaking, probably because it lives pretty close to the header.

So, if the current draw of the pump is 5 amps or less, you should be able to get by without the relay.

 

Which terminal on the switch?

 

My guess Ignition 1 could go the I terminal and the S terminal to Ignition 2 . Ignition 2 should be for the resister bypass and only hot with the switch in the start position.

 

do you have the original wiring diagram for the vehicle the switch was used on? I bet I have one around here, somewhere...but I'd have to guess about which switch it is.

Do you have a multimeter? you can measure the resistance from the BAT terminal to the IGN1 and IGN2 terminals, when the switch is in different positions, and figure it out.

 

Do you have a 12V test light or a volt meter? If not, now is the time to get one (both). With a test light, connect the ground clip to a solid ground position under the dash, then turn the ignition switch to the "On or "Run"" position, that is the position where the key sits when the engine is running. YOu don't have to start the engine, just turn the key to that position. Note, some switche's have an "Accessory" position, which is one position before the "Run". You could actually use either, but I would use the Run terminal. Now with the switch in that position probe the terminals on the switch to find which one illuminates the test light, that's the one to use.

With a meter the procedure is basically the same, clip the ground probe to a solid ground point, set the meter to read DC volts for 6 or 12 volts (probably use the same position, often that is 0 - 20 volt range), and probe the terminals until you find the one with voltage present.

Note, be careful when probing these terminals so that you don't short the probe against something else that can conduct electricity, or you will get some sparks flying, and maybe a blown fuse and a permanent burn mark on the probe.

 

Simplest place to pick up power for that would the positive side of the coil. That way the switch will be enabled whenever you want the car to start and run. Plus you don't need to probe around under the dash, or kill your back to connect stuff. If you have a resisted coil, then you pick up power before the resistance.