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I got a new old light switch for my 54 pickup is there any way to test it off the truck with a volt meter i thought i would attach some cables to the hot side turn it on and see what readings i get any thoughts or worries here!!!!! I love fooling around with electrical stuff but I get into trouble sometimes OOOPS... Peter

you dont need to connect cables to it. Just use the continuity (ohms) function and you can see what actuates when you turn the switch on/off.

Hey Pete. Check the Events Section in case you haven't already for an old Chevy truck get together in our area.

I,m not shure about the 54 but most tail & dash lights don,t feed off the main hot wire to the headlights. They have a separate cicuit comeing from the fuse block. It can confuse you when you are testing.

Cjoe can you give me a quick lesson on how to use the OHM part of my multi meter to test those points . I asumme each post should show some resistance and if it does then that part of the switch works. Also I would think that the most likely part of the switch to break would be the off on portion and the reostat part to turn the dash lights on... Peter

Peter,

The main purpose of the OHM function is to read resistance between two points...for the average handyman, this function is used mainly to find continuity, or a good path between any two points.

On any scale, sticking the probes together will deflect the needle and tell you 'things are touching'. It's the same deal when you check your light switch. Stick one probe on a terminal, and with the other probe you will be able to see which terminals are connected electrically to the first.

It lets you see what is hooked to what when the switch is open, closed, on 'park' etc.

Select the function that might read RX10, or some such thing. You will know it because when both probes are touched together, the needle will deflect.

Basically, this function shows a path between one probe and the other probe. Technically it will do more than just show continuity.

Sorry for stealing the spotlight Carl...it's the mad scientist in me!

Stuart

You know your my hero cousin Stuart.... Peter

no sweat Stuart, you are way ahead of me on the electrical end of these old trucks.

Petmil...the only thing I would add (or change) to what automarc has said is that if you are new to using a VOM (volt/ohm meter) I would suggest getting a digital unit. They are quite inexpensive (about $25 for one that is sufficient) and they will give a readout of the function so there is less confusion in understanding the scale. Basically you set the function to continuity (ohms = resistance), you should now have a reading of 1 (showing infinite resistance = open circuit) touch the 2 probes together and you will have a reading of 000 (zero resistance = complete circuit). You do that to verify the meter is working correctly. Next, WITH NO POWER TO THE SWITCH, touch one probe to the battery post of the switch, turn the switch on and watch the readings as you test continuity through each post on the switch. Some switches have more than one on position (parking lights vs. headlights). Be sure to test each post from the battery post at each on position as some lights (taillights & dash lights) will actuate on both positions. Any reading will tell you there is a continuous circuit between these posts at that switch position. Lack of a readout means that post is not actuated with switch in that position (either because it isnt supposed to actuate OR something is faulty). When checking the dash lights you will get varying reading between battery post and dashlight post as you turn the reostat. That will show the correct operation of the reostat in the switch. Good luck and have fun...

Carl