so wiring up headlights n tail lights with a new switch and new wiring. running hot wire (battery) to switch, and then wires for tail, parking and headlights.... when i place switch in ON position, and THEN connect battery the lights work fine.... when i connect battery FIRST, then try to pull switch to ON position, i blow the headlight fuse,,,, what gives? using a painless wiring harness , 12 volt system, all wires a CLEARLY labeled..... obviously there is a fuse to the headlight system which keeps blowing,,,so something is shorting out and killing the fuse....NEW WIRING AND SWITCH...... this is in my 1950 oldsmobile. new sockets and taillights in the rear....car had already been converted to 12 volt and was running newer headlights.... any input is appreciated.... thanks
When you connect the battery with the switch on and the lights come on what happens if you turn the switch off and then back on. Does the fuse still blow?
Get a handful of fuses and start doing process of elimination. Remove all the wires from the switch except for the battery plus wire, turn it on while hooked up. It should not blow. Then put the headlights wires in place and see what happens, if it doesn't blow remove that one and hook up the tail light wires, etc, etc. Just do one circuit at a time till you blow a fuse and that will be your culprit. What amperage fuse is blowing ? You should have maybe a 25 amper on the headlights and a 15 on the tail lights, but that is just a guess. Don
the fuse is a 30a .....idk why it keeps blowing...its blowing when i go to first position...thats only to turn on the tail lights.... i havent tried turning off the switch once its on...ill have to see what happens.... would having it bolted to the metal dash have anything to do with it? when i have tested the switch it was always hanging....and not installed on the dash...where its making metal / metal contact against the dash...... if it is somehow grounding off the dash...how can i get around that> i will trouble shoot it tomorrow with lotsa fuses! i would like to be able to use this switch as it cost me some $$
What Don said is the best way to test each load on the circuits going to the switch. On thing I might add is to use a 30 amp circuit breaker for testing instead of blowing a bunch of fuses.
Remove all bulbs, then reinstall one at a time, when the fuse blows you will know what circuit to track down. The bulb might also be your culprit!
I think this part of your post is the smoking gun: ___________________________________________________________ so wiring up headlights n tail lights with a new switch and new wiring. running hot wire (battery) to switch, and then wires for tail, parking and headlights.... when i place switch in ON position, and THEN connect battery the lights work fine.... when i connect battery FIRST, then try to pull switch to ON position, i blow the headlight fuse,,,, ___________________________________________________________ Here is what I suspect. When you hook up the battery with it in the ON position, you are not putting any finger pressure on the switch. But when you pull out the switch you are possibly pressuring it into touching the metal dash, or maybe the switch has a defect in it. As I see it, as long as you aren't touching the switch it works ok, so that is sort of a red flag to me. Check the back of the dash for a spot where a wire or ring terminal may be touching bare steel when you are pulling on it. Remove the entire switch from the dash and hang it down below and see how it works then. Don
I had this problem when wiring a new build. I used a new switch from an aftermarket hot rod supplier. It was one of the cheap switches that is labeled "Lights" on the knob, basic pull out two click deal. Anyway, it would randomly blow the fuse when pulled out and I used a meter to determine that the switch was shorting internally. The plunger was grounding out internally as it was pulled out. If I turned the battery off, pulled the lights on and turned the battery on it was fine. I swapped the switch out for a junkyard OEM switch and haven't had any trouble since.
If you substitute a 12 volt bulb where your fuse goes, you can see if you have a short (bulb will glow), and it saves blowing lots of fuses. When you have found the culprit and fixed it, replace the fuse. A taillight bulb works well.
Well heres whats happened. Got new fuses from AZ 30 amp just like what I had been blowing. Began testing the switch with different loads. Tailights didnt blow fuse. Headlights didnt bloe fuse. Put both on and didnt blow fuse. Mounted switch on dash and still didnt blow fuse. Soooooo now everything works the way it should......
So the problem mysteriously fixed itself. And you still don't know the cause of the initial problem. I HATE it when that happens!
Only thing I can think of is that the new fuse can "handle" the initial shock of the first pull on the switch. Posted using the Full Custom H.A.M.B. App!
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