Headlight Switch Question...

Tom Bowman · May 12, 2015

Why would I get ~12.25 volts at the "hot" terminal of the headlight switch (where it feeds up from the key switch), but only ~10.45 volts at the "switched" terminal, that feeds out to the headlights/taillight/worklight?

It's a fused aftermarket switch (A&I, I think). The fuse checks good with an ohmmeter, and the lights work.

I did have a bad ground on the worklight that I had to resolve, which is when I noticed that I only had ~10.45 volts at the worklight. I wanted to see where the voltage drop was occurring, and traced it back to the light switch.

Bad switch? Loose fuse holder/clip thingy on the switch?

Charles in Aus. · May 12, 2015

Very quickly remedied ; remove switch ,place on anvil , adjust with the biggest hammer you have

Some switches are just no good , you are lucky to have found out this one is bad before age and increasing resistance caused a meltdown .

Txturbo · May 13, 2015

that is to much of a voltage drop. Disconnect the wires and check the resistance between those two terminals when in the on position.

Grandfatherjim · May 13, 2015

Check the voltage at both sides of the fuse. If it's the same, the fuse/fuse holder is not the problem.
Most likely dirty contacts within the switch. If you're really enthusiastic maybe the switch will come apart and it will be possible to clean the contacts. If they aren't all pitted or corroded, a pencil eraser is about the right "abrasiveness" for cleaning contacts.

However the best bet is likely the fine-tuning-with-an-anvil-and-buy-a-new-switch method mentioned above.

Tom Bowman · May 13, 2015

Thanks, all. I picked up a different switch today.

I'll see if I can diagnose the bad switch, before I give it the recommended "adjustment". :wink:

Tom Bowman · May 21, 2015

I installed the new switch...and I'm still getting the same voltage drop from one side of the switch to the other. What's the deal?

Ark68SS · May 21, 2015

(quoted from post at 17:17:23 05/21/15) I installed the new switch...and I'm still getting the same voltage drop from one side of the switch to the other. What's the deal?

Do a voltage drop test on the switch. Use a digital voltmeter set to ~2 volts or less. Put the positive lead of the meter on the switch post with the power wire, put the negative lead on the switch post with the wire that feeds the lights. Turn the switch on and observe the reading on the meter. It should be less than .2V. If it's higher, that means there is too much resistance in the switch contacts. It's better to do this test with the motor running so that the battery charge is being maintained.
BillL

Headlight Switch Question...

Tom Bowman

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Charles in Aus.

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Txturbo

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Grandfatherjim

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Tom Bowman

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Tom Bowman

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Ark68SS

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