I thought I was being real smart when I used the stock D2 fog light wiring to hook my new after market fogs up, but they have blown the fuze twice. They worked, turn on and off through the stock switch but only stay on for an hour or so before they blow the 15amp fuze. I've tried it twice. The new fogs are 55watt, same as the factory hella fogs. What am I missing? can I put a 20 amp fuze in. Sorry if those are dumb questions. I'm a electronic rookie.

I did manage to relocate my wiper fluid bottle though...yeah me!

 

Well, if what you say is correct by specification, the amp drain is a little under 5 amps (closer to four) for each bulb. So the 15 amp fuse should be doing the job. The schematic shows nothing else for fuse 3, under hood, the output is switched by the front fogs relay. So, we could have (a) mis-labeled new fog lamps; (b) ground (skint wire) on system, not a hard short, but drawing something that when you add fogs tips the scales; (c) loose wire or connector for fuse 3. A carbon coated connector heats up when pwer runs through it, and conducts that to the fuse, which is on the verge of melting anyway.

My suggestion is to remove the fuse, and and remove both fog lamps from the circuit. Put meter on DC volts, and plug the leads into where the fuse came out of, fog lamp switch on and relay engaged. If you get any volt reading, there is a partial short, or some pirate wire added on for something else (ground effects to illuminate the glistening oil sheen...). If amp meter is rated enough, switch to amps and connect one fog bulb to see how many amps it draws (some meters will do 10 amps, some people have DC clamp on meters, etc.).

Can't advise 20 amp fuse, because wire is most likely not the correct gauge for it. Would want to know why 8-10 amp load is blowing a 15 amp fuse slowly. usually this is because there are more amps from something else installed by attorney Murphy, of Murphy's Law...

 

How many lights did you add? Are you still using the factory fogs? The math works like this:
1. Add together all of the watts for each bulb. The factory fog lights are 55 watts each. So 4 x 55w equal 220 watts. 2 factory fogs + 2 after market fogs.

2. The max wattage a circuit can handle is the voltage * the fuse rating. So 12volts * 15 Amp fuse equals 180watts max. Discos, like most vehicles, usually run between 13 & 14 volts. So 14 volts * 15 amps equals 210 watts. Assuming you have 4 x 55 watt bulbs, you are at least 10 watts over the max. Which explains why it's popping slowly, you're barely over the max and the fuse is taking it's sweet time heating up.

Will replacing the fuse with a 20 amp one work? Yes, but, as pointed out previously, that's generally a bad idea. The wiring might not be rated for 20 amps, higher amps bring more heat which will melt the wire's insulation and set your truck on fire.

 

Dang, I did not think about doubling up on the fogs. Duh... If this is the case, run a second fog relay, to be turned on by the existing fog circuit. It can handle the extra relay coil with no problem. Use that relay to switch on 12 volt power from another source to the new lights. BE SURE to use an in-line fuse holder very close to the new source of power. Auto parts store will have all this, and even a little plate that attaches to battery to provide extra connection points.

 

Thanks for the info. No, i'm not useing the factroy fogs. If I was then I wouldn't need the afer market fogs. I pretty much chopped the connectors off the factory fogs and attached them to the new fogs then plugged them in. I'll double check the grounds on the new fogs. If it doesn't work then i'll just have ot hook up an independant switch kit for the fogs.

Thanks again.

 

I installed a 20AMP fuze and the after market fogs have been running great on the factory switch. That was a few months back.

 

Remember the old fuse that kept blowing? It was made out of a metal alloy that melts, at a certain number of amps. What you have done is transfer the heat that melts the correct size fuse to the wiring connectors somewhere in your harness. Eventually one or more may start turning brown to black, insulation can melt back away from connector, connectors can heat and oxidize and heat more. Depending on where this happens, it could expose your truck to an electrical fire. Once the plastic foam used in the dash, door panels, etc. is ignited, truck will burn up in less than five minutes. You'll find plenty of vehicles in the junkyard that burned because Bubba put in a stereo, kicker amp, CB with linear, or what ever, and used no fuse or wrong fuse.

Can you get away with it short term? Depends. Long term? The laws of physics are against you. Most factories seldom put in larger wire than needed in a harness, if 16 gauge will do, they won't throw in 12 gauge, they want to save 12 cents per harness X 100,000 vehicles. Bean counterz rule!

 

x2. Install a relay fed from the battery and controlled by the fog circuit.
Compare that $10 update to what your insurance deductible will be when your car burns up.

 

5 amps? Really? Also the lights are not any more powerful then the stock fogs.They are 55w ,same as the factory hella fogs.
Regardless, these are fogs and it's not always foggy. They haven't seen mnuch action.

 

Ask yourself this... if two 5 amp fog lamps are blowing a 15 amp fuse,... might there be something else to look for? Yes, you got yourself off the trail and back home with the 20 amp. Your post will live for years on this site, maybe have several hundered to several thousand visitors. I'm sorry, but I must speak up and tell people what I feel is the right way and why. A newbie from LA (lower Alabama) might hook up more lights to go out to his favorite gator wrasslin' hole....