Horn/Cigar lighter fuse keeps blowing.

[DerekTheGreat]

Hello again, its me.

The horn will work for maybe 1 second before the fuse blows. This issue is new, seems to have popped up after the 3G swap and not sure if the cigar lighter will also cause the fuse to pop. Are the horns bad? Ok, I'll admit that I touched the charge wire to ground and produced some sparks when I did it.. That wouldn't be enough to melt wires somewhere would it? So far fuse only blows when horn button is pressed, so thats why I am thinking the horns themselves or maybe even the relay? My wiring diagrams are for Fords and Mercury stuff, not sure if circuit is same for Lincoln.

What say you fine folks?

[gadget73]

horns or relay is a fair guess. Unplug the horns and see if the fuse blows. there are 2 horns, so it could be either one or the wiring between.

[DerekTheGreat]

Thanks gadget, I'll do that.

[85crownHPP]

Horns definitely like to blow fuses when they start to go bad.
I really like the horns off the 2000+ town cars, I have/plan to have them in all my vehicles, even the scooter

[DerekTheGreat]

I think that's what the issue is too. Not that I'm an electrical expert but I'm questioning the relay deal, that just can't be bad, it's not the guy that goes to ground. (edit, yeah it does, duh. Horn button grounds that out and then it dumps power to horns. Like it was said, I'll unplug the horns, press the button and if fuse pops, dinner is served.) Wouldn't things that could cause the circuit to pull more amps be lower than expected resistance & a short right to ground? I took a look around and the blue wire going to the driver's side horn has a gash in the insulation but the passenger side looks fine. I was planning on relieving that '89 we found of its horns and relays for good measure. What's great about the 2000+ TC horns? Direct fit? Also, what should the resistance of the horns be?

[gadget73]

Yes. The horns tend to short internally when they die, so more load. Not sure on proper resistance, since you have access to a car that isn't blowing fuses I'd probably just measure those for reference.

[DerekTheGreat]

Wow, I'm an idiot. Duh, just use Ashley's car.

[sly]

Should be around 1.5 ohm or more for good horn.

[DerekTheGreat]

Thanks Sly. Fingers are itching. Stupid baby shower for her sister is preventing me from fixing this...

[DerekTheGreat]

I've been served plenny of whiskey though heheheh

[DerekTheGreat]

Update..

Sunday we went back to the yards and I pulled both horns and the relay for good measure off of that one Town Car. Tried them on a battery and they worked, for whatever that's worth. Concerned me that the lead for the horns (Dark blue wire) was exposed a great deal and another wire for a separate relay had the same thing going on as well, donor car was also like this.

Updates:
1) Found no issues with my relay or wiring, system grounds out the relay like it supposed to.
2) With the original horns both would blow the fuse almost instantly when run together (with any relay I used too). Either horn running separately, no issues.
3) Pulled low note horn (driver's side) and measured resistance, I got 0.5 ohms so I figure that's my short. Checked junkyard unit, 0.6 ohms. Hmmmm... Tried adjusting that knob thing in either direction but that didn't really increase resistance at all. Manual basically states you only use that to make the horn work again if it isn't and only adjust it by a 1/4 of a turn or so. I checked the high note horn I got from the yard and it measured about 25 ohms...
4) I pulled Ashley's horn as she had no problems with hers (she's really happy with me right now lol) and it also measured 0.6 ohms but I slapped it in place. I cleaned up the threads & stuff and used that silver antisieze stuff on the bolt and washer (hope that wasn't a bad idea). It worked for a little while but then I noticed the horns grew weak after about three 2 second instances of horn blowing and it has started to blow fuses again... What gives?

Based on your experiences, too much resistance in a circuit wouldn't blow a fuse, right? Fuses only go when there's a short to ground somewhere? Makes sense in my mind as no resistance seems to mean super high rate of current thus blown fuse, where as high resistance means less current flow. Please fix any stupidity here. If I can find new horns I'm going to buy both and see what it does, otherwise it's off to the dealer for this one. F'n stupid.

[gadget73]

well, Vols = current * resistance, or current = volts / resistance, so with 12 volts across 0.6 ohms, you're at 20 amps. Add in wire resistance and its probably still around 10 amps. At 25 ohms, you're right around half an amp of current. Higher resistance = lower current, directly in proportion.

[sly]

anything under 1 ohm should be considered bad. 13.6V is about the nominal for most any current calculation... so 0.5 ohms should give you over 26 amps. You want horns that are higher than 1 and much higher preferably. I didn't check the new Wolo horns I got at the parts store for my 88, but I can when I get home. 25 ohms sounds like a very good one to me. I'm betting the one from Ashley's car is also close to being done too.

[85crownHPP]

If it acts the same with horns that are nice and loud on the other car, I'd suspect a pinched wire or other short somewhere. There's a good chance the horn wires are in the same harness as the alternator wiring that goes into the interior, how deep did you go when you wired up the 3G?
Current has to be flowing somewhere excessively for a fuse to blow, try to think of any wiring you could have disturbed between the relay and the horn, even in past projects.
I'd rig up some jumper wires and test all the horns directly with a battery, just to triple check them.

[sly]

the horn fuse should be 20A but it's also got a few other things on that circuit. If one horn is less than 1 ohm, that means it's pulling more than 12 amps when you poke the button. Not a good scenario for fuse longevity. A good horn should pull less than or maybe 1 amp How else can HiFiMerc have 11 horns on his car and still only be using the one circuit. If the good ones are about 25 ohm... then they will be pulling about half an amp. I'm thinking you're dealing with old car syndrome with both cars a bit here. Kinda like I did with my 88, but you don't have a short between the fusebox and firewall that just pops the fuses as fast as you can poke them into the fusebox. At least you have to push the horn button to actually blow the fuse. Though it might be a good idea to check for wire issues. The horn wires are pretty exposed. At least on every car I've seen, the last 6-10 inches are not in loom at all.